Institut für Textiltechniklib.ugent.be/fulltxt/RUG01/001/418/392/RUG01-001418392... · 2010-09-08 · Institut für Textiltechnik S t u d i e n a r b e i Masterarbeit t ... France

Institut für Textiltechnik

S t u

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Mas

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2008

Processing, morphology and product parameters of PVDF filaments for biomedical applications

Abid Omar

Association of

Universities for Textiles

Rheinisch - Westfälische Technische Hochschule

Aachen

Institut für Textiltechnik der RWTH Aachen

Prof. Dr.-Ing. Dipl.-Wirt. Ing. Thomas Gries

Fakultät für Maschinenwesen

Diplomarbeit Vorgelegt als:

von:

Diese Arbeit ist nur zum internen Gebrauch bestimmt. Alle Urheberrechte liegen beim Institut

für Textiltechnik der RWTH Aachen. Für den Inhalt wird keine Gewähr übernommen.

Betreuende Assistentin:

Aachen, August 2008

Dipl.-Ing. Stéphanie Houis


Matr.-Nr.: 285005

Abid Omar

Masterarbeit

Abstract 2

Abstract

Poly(vinylidene fluoride) (PVDF) has become an established polymer in both general

and biomedical applications. Its properties include its interesting ferroelectric behavior

of piezo- and pyro-electricity, excellent biocompatibility and chemical resistance. As a

thermoplastic polymer, it is easily processed to solids, films, textiles and coatings.

There has been an immense amount of research in studying and understanding its

unique properties, especially of its ferroelectric effects from the beta-phase

conformation. However, research of its properties in the textile form as filaments has

been very limited.

This project establishes the processing parameters for melt-spinning PVDF filaments,

and analyzes the morphology and product parameters of the formed filaments. PVDF

filaments were successfully spun from 90–340 dtex in 24 and 72 filaments of round

cross-section. Different crystalline structures were achieved by changing process

parameters of draw temperatures and draw ratios. Analysis by tensile testing, contact

angle evaluation, differential scanning calorimetry and x-ray diffraction was carried out.

The draw temperature was confirmed to have the most significant effect on achieving

the different crystalline structures, with a draw temperature of 70 °C resulting in the

highest alpha to beta phase transformation.

Keywords: Poly(vinylidene fluoride), PVDF, filaments, morphology, biomedical

Acknowledgements 3

Acknowledgements

I gratefully acknowledge everyone who helped me and supported this project at the

Institut für Textiltechnik der RWTH Aachen (ITA), especially David Djudjaj at the ITA

Spinturm (INNOTEX).

Additionally I thank the people at the Deutsches Wollforschungsinstitut an der RWTH

Aachen e.V (DWI) who went above and beyond the call of duty to assist in my project.

Prof. Dr. Crisan Popescu and his Ph.D students were instrumental in DSC analysis. I

would like to acknowledge the help of Dr. Zhu Xiaomin for arranging x-ray diffraction

analysis with Dr. Dimitri A. Ivanov at the Institut de Chimie des Surfaces et Interfaces

(ICSI) in Mulhouse, France. Additionally, Brigit Mohr, Vishal Goel and Mohamed

Salama Moustafa were of assistance.

I could not have done it without my support system in fellow E-TEAMer Britta Michalski.

Finally, I would like that thank Dipl.-Ing. Stéphanie Houis for her gentle supervision.

Copyright information

The author gives admission to make this Master’s thesis available for consultation and

to copy parts of the Master’s thesis for personal use. Any other use falls under the

limitations of the copyright, especially with regard to the obligation of mentioning the

source explicitly on quoting the results of this Master’s thesis.

Abid Omar

Aachen, 20 August 2008

1 Introduction 4

Table of contents

1 Introduction ........................................................................................................ 9

1.1 Objectives ............................................................................................................ 9

2 Literature review .............................................................................................. 11

2.1 The poly(vinylidene fluoride) molecule ............................................................... 12

2.1.1 Synthesis of poly(vinylidene fluoride) ................................................................. 12

2.2 Crystal structure and morphology ...................................................................... 13

2.2.1 Polymorphism .................................................................................................... 13

2.2.2 Phase formation and transformations between phases ..................................... 16

2.3 Ferroelectric phenomena ................................................................................... 17

2.4 Properties ........................................................................................................... 18

2.5 Commercial aspects .......................................................................................... 19

2.6 Applications ........................................................................................................ 19

3 Experimental .................................................................................................... 21

3.1 Material .............................................................................................................. 21

3.2 Spinning ............................................................................................................. 21

3.2.1 Melt-spinning plant ............................................................................................. 21

3.2.2 Spinning terminology ......................................................................................... 23

3.2.3 Spin plan for yarn production ............................................................................. 24

3.3 Linear density ..................................................................................................... 25

3.4 Tensile testing .................................................................................................... 26

3.5 Wetting and surface energy ............................................................................... 26

3.5.1 Measurement theory and methods .................................................................... 26

3.5.2 Experimental ...................................................................................................... 28

3.5.3 Experimental procedure ..................................................................................... 29

3.6 Differential scanning calorimetry ........................................................................ 31

3.6.1 Interpretation of double endotherms .................................................................. 31

3.6.2 Experimental procedure ..................................................................................... 32

3.7 X-ray diffraction .................................................................................................. 33

4 Results and discussion ................................................................................... 34

4.1 Spinning of PVDF filaments ............................................................................... 34

4.1.1 Spinning of ultrafine filaments ............................................................................ 35

4.2 Linear density ..................................................................................................... 35

4.3 Tensile testing .................................................................................................... 35

4.4 Wetting and surface energy ............................................................................... 37

1 Introduction 5

4.4.1 Contact angle and material constant determination ........................................... 37

4.4.2 Surface energy determination ............................................................................ 38

4.4.3 Conclusion ......................................................................................................... 38

4.5 Differential scanning calorimetry ........................................................................ 40

4.5.1 1st heating scan .................................................................................................. 40

4.5.2 Cooling scan and 2nd heating scan .................................................................... 42

4.5.3 Polymorphism .................................................................................................... 43

4.5.4 Conclusion ......................................................................................................... 44

4.6 X-ray diffraction .................................................................................................. 47

4.7 Comparison of XRD and DSC results ................................................................ 49

5 Conclusion ....................................................................................................... 50

5.1 Future scope ...................................................................................................... 50

6 Bibliography ..................................................................................................... 52

7 Appendix ........................................................................................................... 55

8 Declaration ....................................................................................................... 59

1 Introduction 6

List of figures

Figure 2.1 Schematic representations of PVDF β-, α- and γ-phase molecular conformations (left to right) [1] ........................................................................... 13

Figure 2.2 Crystal structure of the α-phase of PVDF is in the TGTG′ conformation [12] .................................................................................................................... 14

Figure 2.3 Crystal structure of the β-phase of PVDF is in the all-trans conformation [12] .................................................................................................................... 14

Figure 2.4 Molecular orientation in (a) the γ-phase and (b) the δ-phase [12] ............... 15

Figure 2.5 Schematic diagram of the spherulitic morphology of PVDF [12] .................. 16

Figure 2.6 Transformations between the four main phases of PVDF [13] .................... 17

Figure 3.1 Illustration of extrusion section of bi-component melt-spinning plant ........... 22

Figure 3.2 Illustration of takeup module of bi-component melt-spinning plant .............. 22

Figure 3.3 Wetting of a surface and contact angle measurement [27] .......................... 26

Figure 3.4 Wilhelmy method for contact angle measurement ....................................... 27

Figure 3.5 Sample preparation for Washburn adsorption measurement [29] ............... 29

Figure 3.6 Rate of adsorption for hexane and water for determination of material constant and contact angle................................................................................ 30

Figure 4.1 Optical micrographs for 24 filament (left) and 72 filament (right) yarn specimens ......................................................................................................... 34

Figure 4.2 Stress-strain behavior for sample V5 is typical of PVDF fibers .................... 36

Figure 4.3 Strength and elongation vs. draw temperature and draw ratio for samples V1–V15 ............................................................................................... 36

Figure 4.4 Contact angle vs. draw ratio and draw temperature for samples V1–V15 ... 38

Figure 4.5 DSC thermograms for the 1st heating scan .................................................. 40

Figure 4.6 DSC thermograms for the cooling scan and 2nd heating scan ..................... 42

Figure 4.7 Degree of crystallinity vs. draw temperature and draw ratio of the α- and β-phase according to curve fitting on DSC thermograms .................................. 44

Figure 4.8 Degree of crystallinity vs. draw ratio and draw temperature according to DSC results ....................................................................................................... 44

Figure 4.9 DSC thermograms for samples V6–V8 with Gaussian-fit curves ................. 45

Figure 4.10 DSC thermograms for samples V12–V14 with Gaussian-fit curves ........... 46

Figure 4.11 X-ray diffractogram for PVDF V9 shows mostly β-phase ........................... 47

Figure 4.12 X-ray diffractogram for PVDF V12 shows a mixture of α- and β-phase ..... 48

Figure 4.13 X-ray diffractogram for PVDF V13 shows pure α-phase ............................ 48

1 Introduction 7

List of tables

Table 2.1 Selected physical and thermal properties of Solef 1006 PVDF .................... 18

Table 2.2 Producers and trademarks of poly(vinylidene fluoride) resin ........................ 19

Table 3.1 Temperatures used in the extrusion zones ................................................... 21

Table 3.2 Spinneret specifications ................................................................................ 23

Table 3.3 Drawing and winding parameters .................................................................. 25

Table 4.1 Tensile testing results for samples V1–V15 .................................................. 37

Table 4.2 Material constant and contact angle values .................................................. 39

Table 4.3 DSC results for 1st heating scan .................................................................... 41

Table 4.4 DSC results for the cooling and 2nd heating scan ......................................... 43

1 Introduction 8

Abbreviations and symbols

CV Coefficient of variation

dpf dtex per filament

DR Draw ratio

DSC Differential scanning calorimetry

DT Draw temperature

DUO First godet roll pair

H Enthalpy or heat of fusion (J/g)

ID Sample identification

ITA Institut für Textiltechnik der RWTH Aachen

MONO 1 Second godet roll (with temperature control)

MONO 2 Third godet roll (with temperature control)

N Number of experiments

PE Poly(ethylene terephthalate)

PTFE Poly(tetrafluoroethylene)

PVDF Poly(vinylidene fluoride)

SD Standard deviation

Xc Degree of crystallinity (%)

XRD X-ray diffraction

1 Introduction 9

1 Introduction

Poly(vinylidene fluoride) (PVDF) is a thermoplastic fluoropolymer with excellent

engineering properties and has found many uses in industrial applications as an

established polymer. Properties include interesting ferroelectric behavior of piezo- and

pyro-electricity, excellent biocompatibility and chemical resistance.

There has been an immense amount of research in understanding and harnessing

these ferroelectric properties of PVDF. This was the first polymer found to exhibit these

unique electrical properties, with the discovery of it piezoelectric behavior in 1969 [1].

The ferroelectric behavior originates from the β-phase crystalline structure of PVDF.

These ferroelectric properties have since been found in other polymers too, however

PVDF exhibits a much more significant ferroelectric effect than the other polymers,

similar to that of quartz. Thus, PVDF has many interesting applications already as

transducers and dielectrics.

PVDF also has significant potential for biomedical applications, by virtue of its excellent

biostability and biocompatibility. It is already being used as medical sutures, where it

also exhibits improved elasticity and strength over polyester and polypropylene, two

other polymers used for medical sutures. Additionally, PVDF has obvious applications

in implant engineering.

While there has been a lot of research in the crystalline structures of PVDF and in

understanding the origination of its ferroelectric behavior, most of this research has

been limited to the polymer as a film.

1.1 Objectives

The objectives of this project are to conduct a thorough literature review with a focus on

research on the textile properties and processing of PVDF. PVDF multi-filament yarn

will then be produced on a state-of-the-art melt-spinning extruder by Fourné

Polymertechnik GmbH (Alfter, Germany). Different spinning parameters, namely the

draw ratio and drawing temperatures will be used which are expected to result in

different crystalline structures of the filaments. The spinning parameters will be

specified according to the literature review to result in the formation of different

crystalline structures in the yarn.

The effects of different crystalline structures on the textile and other characteristics of

the PVDF filaments will be analyzed. These are expected to have an effect on the end

applications of PVDF, especially in biomedical applications such as tissue- and

implant-engineering. Understanding the effect of the different structural characteristics

of the produced PVDF filaments, as well as establishing the methods to produce them,

1 Introduction 10

are expected to aid in the selection of optimal properties of PVDF in biomedical

applications. The effect of the different yarns produced will be evaluated for biomedical

applications as part of the bigger project by cell seeding.

Within this project the produced yarn will be evaluated using physical textile testing and

supplemented by other analytical techniques such as wetting and contact angle

evaluation, differential scanning calorimetry, and x-ray diffraction.

2 Literature review 11

2 Literature review

Poly(vinylidene fluoride) (PVDF or PVF2) is a fluoropolymer that was first successfully

synthesized by E.I. du Pont de Nemours & Company, Inc. (Delaware, USA) in 1944 [2],

soon after the serendipitous discovery of the first fluoropolymer,

poly(tetrafluoroethylene) (PTFE) in 1938 [3]. PVDF was successfully commercialized in

the 1960’s, whereupon it quickly found successful applications in architectural coatings

and plenum wire1 coating, where its properties as a fluoropolymer of high temperature

and chemical resistance as well as long-life were important. Today PVDF has become

the second largest volume fluoropolymer after PTFE.

The discovery of the piezoelectricity in PVDF by Kawai in 1969 [1] sparked immense

research interest in this polymer. Previously, piezoelectricity was known in crystalline

materials: quartz is a universal example. In the 1950’s, Fukada [4] found the

piezoelectric effect in various biopolymers, including wood, dry bone, tendons and silk,

and certain ceramics [5]. Piezoelectricity had already found a wide array of

applications, starting with sonar in 1917 to being prevalent in timekeeping as watches

and clocks, and being ubiquitous in electronics such as in transducers today. The

piezoelectric effect in biopolymers could have potentially remarkable applications in

healthcare. For example, Fukada [4] mentions that weak current flows through the

bone were already found to accelerate bone growth. Electrotherapy — the use of

artificially produced currents to affect human health — was a focus of research then,

and in spite of the increasing use of electrotherapy today, the questions then remain as

relevant today [5-7].

Thus, in a wide-ranging search for piezoelectricity in polymers, the presence of

relatively ‘large’ piezoelectricity was discovered in stretched and poled films of PVDF

by Kawai [1]. This was followed by the discovery of large pyroelectric and nonlinear

optical effects (second order harmonic generation) [8-10] as well as the hypothesis that

PVDF was ferroelectric, which too was discovered soon after [11]. Similar ferroelectric

properties were discovered in other polymers too, such as nylons, but the effects were

significantly lower than that of PVDF and its copolymers [12].

1 Plenum wires are wires that are used in the plenum space -- enclosed spaces (in buildings)

used for heating, ventilating, and/or air-conditioning airflow.


2.1 The poly(vinylidene fluoride) molecule

PVDF is a semi-crystalline polymer, with approximately half of the molecules in the

amorphous or non-crystalline phase, and half in the crystalline phase. PVDF has a

relatively simple molecular structure

(CH2CF2)n

where n is typically greater than 10,000 [12]. Its structure can be seen to be

intermediate of poly(ethylene) (PE) and poly(tetrafluoroethylene) (PTFE) with regard to

the number of fluorine atoms. Interestingly, the properties of PVDF are similarly

intermediate of PE and PTFE.

2.1.1 Synthesis of poly(vinylidene fluoride)

PVDF is the addition polymer of 1,1-difluoroethene, commonly known as vinylidene

fluoride (VDF or VF2). It is generally prepared by free-radical initiated polymerization in

an aqueous emulsion or suspension [13].

“A perfect molecule would have all the carbon atoms bonded to hydrogen atoms

attached only to carbon atoms bonded to fluorine atoms” [12]. However, a certain

fraction of the monomer units are reversed when the molecules are synthesized to a

polymer. These are ‘defects’ within the polymer backbones — namely of ‘head-to-head’

(–CF2 attached to –CF2) or ‘tail-to-tail’ (–CH2 attached to –CH2) units.

The concentration of these defects depends on the synthesis conditions and has an

important impact on the formation of the various polymorphs. At a higher percentage of

these monomer inversions, the β-phase becomes more energetically stable [14], thus

leading to a higher β-phase content.

The ferroelectric property of PVDF results from its β-phase crystalline structure, and

thus there is immense interest in controlling the monomer inversion during synthesis.

The interest in PVDF copolymers also stems from these defects, with the copolymer

mimicking the role of the monomer inversions in a more controlled manner. Other

polymerization processes, such as radiation-induced polymerization, focus on

promoting the formation of particular crystalline phases, but have not achieved

commercial significance.


Figure 2.1 Schematic representations of PVDF β-, α- and γ-phase molecular

conformations (left to right) [1]

2.2 Crystal structure and morphology

PVDF is well known for its polymorphism, with at least four phases found

experimentally. The different phases of PVDF can be characterized by the

conformations of the –CH2– and –CF2– in the polymer chain. The main phases are the

all-trans β-phase, TGTG′ α-phase and T3GT3G′ γ-phase represented schematically in

Figure 2.1 (left to right). The view is parallel to the chain axis, where the large circles

are for fluorine atoms and small circles for carbon atoms. The hydrogen atoms are left

out for clarity.

2.2.1 Polymorphism

The four experimentally found phases of PVDF are the α-, β-, γ- and δ-phase, and a

fifth hypothetical ε-phase.

Alpha α-phase

The α-phase (form II) is the most common polymorph. It forms during polymerization

and crystallizes from the melt at all temperatures. It is non-polar and does not exhibit

ferroelectricity. Figure 2.2 shows the crystal structure of the α-phase. The α-phase has

a trans-gauche-trans-gauche' (TGTG′) conformation.

Beta β-phase

The β-phase (form I) has been the most extensively studied molecular conformation of

PVDF as it is responsible for the ferroelectric properties. It is in an all-trans (TT)

conformation. “The fluorine atoms are too large to allow a simple all-trans conformation

and it is believed they are statistically offset as depicted by broken lines in Figure 2.3”

[12]. Thus the c-axis repeat is in a zigzag arrangement, with the –CF2 groups deflected

to the left and right of the plane of the zigzag.

The β-phase is typically obtained by drawing α-phase films. It is relevant to note that

poling under a high electric field at high temperature is necessary to render the useful

ferroelectric properties of the β-phase. Poling results in a reorientation of the dipoles in

the crystalline phase.


Figure 2.2 Crystal structure of the α-phase of PVDF is in the TGTG′ conformation [12]

Figure 2.3 Crystal structure of the β-phase of PVDF is in the all-trans conformation [12]


Figure 2.4 Molecular orientation in (a) the γ-phase and (b) the δ-phase [12]

Gamma γ-phase

The third phase is the γ-phase (form III) shown in Figure 2.4 (a). The molecules are in

the T3GT3G′ conformation, and can be considered an intermediate between the α- and

β-forms. This phase forms during melt crystallization at temperatures above 160 °C

and reaches its highest value close to 170 °C [15].

Delta δ-phase

The fourth phase is the polar δ-phase (form IV) shown in Figure 2.4 (b). It is also

known as the polar form of α-phase (αp), and is generally obtained by polarization

under a strong electric field. Thus, this form has the same unit-cell dimensions and

chain conformation as the α-form, the difference lying in inter-chain packing alone.

Epsilon ε-phase

A fifth hypothetical polymorph is the ε-phase containing T3GT3G′ similar to the γ-phase

but in an anti-polar arrangement.


Figure 2.5 Schematic diagram of the spherulitic morphology of PVDF [12]

2.2.2 Phase formation and transformations between phases

In most cases, PVDF formed from melt constitutes of the α-phase in the form of

spherulities containing a very low fraction of the γ-phase [12]. The spherulitic

morphology is typical of semicrystalline polymers, and is shown in Figure 2.5.

Generally, the reason for the preferred formation of the α-phase is its higher

crystallization rate at higher temperatures (110–150 °C), whereas the β-phase

crystallizes below 80 °C. As PVDF is mostly crystallized from melt both during

polymerization and processing, it consists mostly of the α-phase. The β-phase is

subsequently obtaining by mechanical deformation such as uniaxial stretching. The

presence of the different conformations is strongly dependent on processing and

electrical, thermal or mechanical treatments that the polymer undergoes. Figure 2.6

summarizes the variety of means of producing the various phases and the

transformations between them.

The α β phase transformation is well known to occur during mechanical deformation

[16], and is one of the objectives of study in this project. The level of transformation is

known to decrease with increasing temperature. Values close to 80 °C are favorable in

obtaining the β-phase, while temperatures close to 130 °C yield mainly the α-phase.

One paper reports the maximum efficiency of conversion occurring at temperatures

between 70 and 80 °C at a draw ratio of 300 % [17]. Another reports the transformation

to occur in the range between 50 and 145 °C, with maximum efficiency at 87 °C [18].

Increasing the amount of α β phase transformation is also possible through other

means, such as ultra-quenching [19], copolymers, polymer additives and blends. One

example is to use a PVDF and poly(methylmethacrylate) (PMMA) blend, which favors

the crystallization of the β-phase directly from melt [20].


Figure 2.6 Transformations between the four main phases of PVDF [13]

2.3 Ferroelectric phenomena

The ferroelectric phenomenon of PVDF is based on the dipole orientation within

crystalline phase of the polymer. This is a polar crystal form, which in the case of PVDF

is the β-phase. The fluorine atoms draw electronic density away from carbon and

towards themselves, leading to strong dipoles in the C–F bonds.

It is necessary to subject β-phase PVDF to an additional polarization treatment to

obtain the ferroelectric properties. This is easily done by poling during α β phase

transformation for example during mechanical deformation at 70–80 °C. Other

procedures include subjecting the polymer to electron irradiation and crystallization

under high electric field.

Extensive reviews of the ferroelectricity (pyroelectricity, piezoelectricity, and nonlinear

optical properties) of PVDF have been done by Lovinger [13] and Kepler [12]. While

these may be of immense interest in medical applications, these are beyond the scope

of this particular project.


2.4 Properties

PVDF is a tough, semicrystalline polymer with excellent engineering properties. PVDF

has high mechanical and impact strength, and excellent resistance to both creep under

long-term stress and fatigue upon cyclic loading. PVDF also has excellent abrasion

resistance and thermal stability, and resists damage from most chemicals and solvents,

as well as from ultraviolet and nuclear radiation. Table 2.1 gives selected physical and

thermal properties of the Solef 1006 PVDF used in this project.

Table 2.1 Selected physical and thermal properties of Solef 1006 PVDF

Property Units Values

Density g/cm3 1.78

Water absorption % < 0.04

Melting point Tm °C 175

Crystallizing point Tc °C 138

Glass transition Tg °C –30

Softening point °C 145

Thermal stability °C 375 – 400


Table 2.2 Producers and trademarks of poly(vinylidene fluoride) resin

Producer Country Trademark

Solvay Solexis SpA Belgium/France Solef, Hylar

Arkema Inc United States Kynar

3M (Dyneon) United States Dyneon

Evonik Degussa GmbH Germany Dyflor

Daikin Industries Japan Neoflon

Kureha Corporation Japan KF Polymer

Zhejiang Lantian Co. China –

Shanghai 3F New Materials Co., Ltd. China –

Chenguang Research Institute China –

2.5 Commercial aspects

PVDF resin is available commercially at a cost of €15-20 /kg from a number of

producers. Table 2.2 is a list of the producers and their respective trademarks of PVDF

resin.

Polisilk SA (Manresa, Spain) is the only known commercial producer of PVDF

multifilament yarn. Polisilk produces a 500 denier (556 dtex) yarn with 42 filaments and

a 1,000 denier (1111 dtex) yarn with 84 filaments.

2.6 Applications

PVDF has many applications especially based on its excellent chemical resistance and

long life as compared to other polymers. General applications include architectural

coatings and wire and cabling. Another application is as hollow fibers in the form of

membranes for purification and separation processes. In processes where purity is

important for water and fluid handling, such as ultra pure water systems,

pharmaceuticals, semiconductors and biotechnology, PVDF is the polymer of choice.

PVDF also has commercial applications as dielectrics and transducers. Its ferroelectric

properties are similar to those of ceramics, whereas PVDF as a polymer has the

advantage of being easily prepared in thin films which are tough, strong and very

flexible. Commercial applications as transducers include speakers and microphones.

Piezoelectric applications include ultrasonics, static pressure sensors, transducers in


medical diagnostics (blood pressure and pulse measurements, ultrasonic cardiac

imaging). Pyroelectric applications are infrared detectors, optical applications.

PVDF has gained substantial use in medical applications. Applications include

implants, generation of soft tissue and nerves [21], suture material, and biomembranes.

Over other biomaterials PVDF has certain advantages, such as better biodurability than

polyester and easier sterilization and higher extension at break than polypropylene

[22,23]. PVDF is used due to its desirable biocompatibility, biostability and satisfactory

mechanical strength, with minimal cellular and tissue response.

Dr. Langer, called one of the father’s of tissue engineering, explains that designing

polymers for tissue engineering is “harder than it looks” because of the complications

involved in biomedical applications. The main challenges are “creating the right

materials that are highly biocompatible and that stimulate the right growth and cell

behavior” [24]. This is a primary motivation for this detailed survey of PVDF as a textile

material and its performance in biomedical applications. The interaction of the

produced PVDF to cell material will be studied as part of the larger project at ITA.

3 Experimental 21

3 Experimental

3.1 Material

Solef 1006, a very low viscosity grade of homopolymer PVDF was provided by Solvay

Solexis SpA (Tavaux, France). This has a high melt flow index of 40 g/10 min at

230 °C/2.16 kg according to ASTM D 1238. Additional physical and thermal properties

relevant to the melt-processing of PVDF 1006 are summarized in Table 2.1.

3.2 Spinning

3.2.1 Melt-spinning plant

A bi-component melt-spinning plant by Fourné Polymertechnik GmbH (Alfter,

Germany) was used for filament production. This is an electrically heated laboratory

scale plant with POY and FDY takeup modules, having takeup speeds from 180 m/min

to 3500 m/min.

Extrusion

Table 3.1 Temperatures used in the extrusion zones

Extrusion zone Temperature [°C]

Spin head 250

Spin pump 250

Extruder zone 1 235

Extruder zone 2 240

Extruder zone 3 240

Extruder head 245

Melt line 245

The bi-component plant is used in a mono-component mode by utilizing only the core

extruder. The temperature zones are given in Table 3.1 along with the temperatures

used during extrusion. The temperatures are based on preliminary testing in an earlier

project at ITA. Figure 3.1 shows the extrusion section of the melt-spinning plant with

the core extruder (on the right), mantel extruder (left side), spin pumps and spin block.

3 Experimental 22

The extruder was run to maintain a pressure of 60 bar, resulting in an average speed of

around 20 rpm. The spin pump was run at 15 and 25 rpm. The specifications of the

spinnerets were used are given in Table 3.2.

Figure 3.1 Illustration of extrusion section of bi-component melt-spinning plant

Figure 3.2 Illustration of takeup module of bi-component melt-spinning plant

3 Experimental 23

Table 3.2 Spinneret specifications

Spinneret A B

Hole cross-section Round Round

Number of holes 72 24

Hole diameter (D) [mm] 0.13 0.40

Length/diameter ratio 2D 2D

Takeup

After extrusion, the polmyer melt is quenched in a laminar air flow at ambient

temperature in the quench cabinet, a spin-finish is applied, then taken up by the first

godet pair (DUO) at ambient temperature, drawn between DUO and the second godet

(MONO 1, with temperature control), wrapped around the thrid godet (MONO 2, with

temperature control), passes through a tension controller, and wound on a bobbin at

the winder. Figure 3.2 is the schematic the takeup module, showing the quench

cabinet, spin finish applicator, godet rolls and winder. The winder parameters for

traverse and tension control are based on recommendations given in the machine

manual, while the other parameters are described in Section 3.2.3.

3.2.2 Spinning terminology

This section defines the terms relevant to the calculations for the spinning parameters.

The spin velocity Vspin is the polymer velocity downstream of the spinneret:

Vspin[m/min] = n . A . ρ

where n is the number of holes, A the area of one hole, ρ the density of the polymer.

The throughput is the extruder output:

throughput g

min = n . A . ρ . Vspin

3 Experimental 24

or throughput g

min =

Tdtex × Vspin

10,000

where Tdtex is the final fineness (titer) of the produced yarn in decitex. Alternatively, the

throughput can be based on the machine setup:

throughput g

min = spin pump speed [rpm] × spin pump delivery

cm3

rev. × density

g

cm3

The takeup speed is the speed of the winder:

takeup speed m

min = throughput

g

min ×

10,000

titer [dtex]

The draw ratio is the ratio of takeup speed and the speed of the first godet pair (DUO):

DR = takeup speed [m/min]

DUO speed [m/min]

The spin/draw ratio is the ratio between the spin velocity and the speed of the first

godet pair (DUO):

spin/draw ratio = Vspin [m/min]

DUO speed [m/min]

The key parameters are throughput and yarn fineness. The calculated throughput can

be verified by measuring the actual throughput after running the extruder for 30

minutes. The calculated yarn fineness can be verified by subsequent measurement of

the linear density (see Section 3.3 and 4.2).

3.2.3 Spin plan for yarn production

The spinning target is to produce multi-filament yarns of 90–340 dtex. The spinning

parameters selected to be varied are the draw ratio, spin/draw ratio and draw

temperatures. These are expected to result in different crystalline structures as

discussed in Section 2.2.2. Additionally, these are expected to have an impact on the

final properties of the yarn.

Drawing and winding parameters

The production parameters are based on the final yarn fineness. Table 3.3 gives the

required winder speed to produce the desired yarns, along with the godet roll speeds

used for the different draw ratios. The godet roll speeds are based on results from

preliminary trials, and set to have the maximum drawing between DUO and MONO 1.

The speed of MONO 2 is higher than the winder speed to allow for relaxation

shrinkage.

3 Experimental 25

Table 3.3 Drawing and winding parameters

Fineness

[dtex]

Draw

ratio

DUO

[m/min]

MONO 1

[m/min]

MONO 2

[m/min]

Winder

[m/min]

Settings for spin pump speed at 25 rpm (throughput = 25.27 g/min)

340 1.0 680 700 730 680

240 1.0 970 1000 1030 970

180 1.0 1290 1330 1380 1290

180 1.5 860 1335–1420 1350–1480 1290

180 2.0 645 1335–1420 1350–1480 1290

180 2.5 516 1340–1420 1360–1455 1290

Settings for spin pump speed at 15 rpm (throughput = 13.96 g/min)

340 1.0 417 427 437 410

240 1.0 585 595 605 580

180 1.0 780 790 800 775

180 1.5 520 785 850–890 775

180 2.0 390 675 845–900 775

180 2.5 310 600 850–870 775

90 1.5 1035 1310 1670 1500

Draw temperatures

The draw temperatures are ambient temperature (≈ 25 °C) and 70, 130 and 160 °C,

and are set for godet roll MONO 1. MONO 2 is kept at a lower temperature to allow the

yarn to cool down before winding. MONO 2 temperature is kept at ambient for ambient

drawing, and at 55 °C for the higher temperature drawing. The draw temperatures are

selected according to the expected crystalline structure formation as discussed in

Section 2.2.2.

3.3 Linear density

The linear density of the yarns is measured using 3 samples of 100 m skeins according

to ISO 2060:2004 Textiles – Yarn from packages – Determination of linear density

(mass per unit length) by the skein method.

3 Experimental 26

3.4 Tensile testing

Measurement of tensile strength and elongation on the produced yarns is carried out

on the Textechno Herbert Stein GmbH & Co. KG (Mönchengladbach, Germany)

Favimat M. The testing standard used is DIN EN ISO 2062:1995 Textilien – Garne von

Aufmachungseinheiten – Bestimmung der Höchstzugkraft und Höchstzugkraftdehnung

von Garnabschnitten [25]. Yarn specimens were taken directly from conditioned

packages and testing using constant rate of specimen extension tensile testers. 30

tests were carried out on each yarn, and the average load-elongation curve is

considered. The initial gauge length is set at 100 mm, initial load at 0.5 cN/tex, and

crosshead speed at 100 mm/min.

3.5 Wetting and surface energy

The surface properties of biomaterials such as wetting and surface energy are

important factors in their suitability for biomedical applications. The contact angle of

PVDF filaments was measured using the Washburn adsorption method against distilled

water. Knowledge of the wettability and surface energy properties of the different PVDF

crystalline structures will help select the optimal structure for biomedical applications.

Effects of higher surface energies are, for example, a decrease in the possibility of

bacterial adhesion and an increase in the deposition of cells [26]. More simply, the

wetting determines the relative hydrophobicity or hydrophilicity of the sample as shown

in Figure 3.3, where the drop A illustrates a very hydrophobic surface (little wetting),

and drop C a very hydrophilic surface (more wetting). Drop A shows a large contact

angle, and C a small contact angle.

Figure 3.3 Wetting of a surface and contact angle measurement [27]

3.5.1 Measurement theory and methods

For measuring the wetting properties of solids, the general method is to optically

measure the shape of a drop placed on the sample. This is a direct measurement of

the contact angle between the baseline of the drop and the tangent of the drop

boundary. The process of measuring this angle is called goniometry.

The contact angle θc is defined geometrically as the angle formed by a liquid at the

three phase boundary where a liquid (L), gas/vapor (V) and solid (S) intersect in

3 Experimental 27

thermodynamic equilibrium as shown in Figure 3.3. The YounG′s Equation [28] defines

the equilibrium contact angle θc

0 γSV γSL γ cosθ

based on the solid-vapor interfacial energy (or surface energy) γSV, the solid-liquid

interfacial energy (or surface tension) γSL and the liquid-vapor energy γ.

In the case of yarns and fibers indirect measurements using a highly sensitive load cell

– such as a tensiometer or a microbalance – have to be used. The available

techniques are the Wilhelmy fiber method and the Washburn adsorption method.

Figure 3.4 Wilhelmy method for contact angle measurement

Wilhelmy method

The Wilhelmy method is a dynamic method for measuring average advancing and

receding contact angles on solids. The wetting force on the solid is measured as the

solid is immersed in or withdrawn from a liquid of known surface tension, giving the

‘advancinG′ and ‘recedinG′ contact angles as shown in Figure 3.4.

cos θ= F

l . σ

The contact angle θc is a function of the surface tension σ of the liquid used, the

circumference l of the fiber and the measured force F. The circumference can be easily

and accurately determined by using a liquid that fully wets and thus gives a contact

angle approaching zero (cosθ = 1).

However, this method was found not to be successful when using very fine fibers of low

stiffness. In the case of PVDF fibers of 7.5 dtex (from a 180 dtex yarn comprising 24

filaments), it was found that the stiffness of the fiber was too low: the fiber would curl

upon contact with the liquid surface, and thus making the measurement impossible.

This drawback of the single fiber method, as well as other disadvantages, are

discussed in an application note [29] by instrument manufacturer KRÜSS.

3 Experimental 28

Washburn method

The Washburn method [30] is based on capillary flow in porous materials. It is

essentially a capillary rise measurement, with the exception that the adsorption by

weight is considered rather than the rise, thus the change of weight as a function of

time

t = A .m2

where the experimental data is mass m [g] of the liquid adsorbed versus the time t [s]

after the solid and liquid have been brought into contact. A is a constant which is

dependent on the viscosity η [mPa], density ρ [g.cm-3] and surface tension σ [mN.m-1]

of the liquid and the contact angle θ on the solid under study as well as its material

constant c

A = η

ρ2σc cosθ

The material constant c is a function of the average capillary radius r and the number of

capillaries nk

c = 1

2π2k5nk

2

The material constant c can be calculated by using a liquid with sufficiently low surface

tension that fully wets the solid and thus gives a contact angle approaching zero where

cosθ = 1. Hexane or heptane have surface tensions of 18.43 mN/m and 20.14 mN/m

respectively and are recommended for material constant determination.

The form of the Washburn equation for contact angle measurement is

cosθ = m2

t

n

ρ2σc

3.5.2 Experimental

The measurements were carried out on a KRÜSS GmbH (Hamburg, Germany) K14

Tensiometer with the KRÜSS K121 Contact Angle Measuring System (version 2.02a)

using the Washburn adsorption method and a standard temperature of 21.0 °C.

Preliminary trials determined that sensitivity at 1 mg and maximum measurement

duration of 60 sec was sufficient to give useful data.

Sample preparation

Spin-finish extraction

The spin-finish was considered to have a notable impact on the surface characteristics.

Methods available to remove the spin-finish are Soxhlet extraction and solvent-based

3 Experimental 29

ultrasonic extraction. Preliminary trials to remove the spin-finish showed that the

resultant fiber mass become notably disoriented and therefore very difficult to prepare

the fibers for contact angle measurement. A sample holder was also tried to keep the

yarn parallel during extraction, however, it was not feasible to prepare the samples

using this holder for the number of tests required. Moreover, it was considered that the

first method would also have an impact on the structural order of the fibers, and

therefore not suitable for evaluating the surface characteristics.

Sample holder

The fibers were placed in a PTFE tube of 1.0 mm inner diameter, 1.6 mm outer

diameter, and thickness 0.3 mm according to the ’straw’ method by KRÜSS [29]. The

PTFE tube was procured from BOHLENDER GmbH (Grünsfeld, Germany). 40 parallel

yarns of 180 dtex were required to give a sufficiently tight fit, 30 yarns of 240 dtex, and

20 yarns of 340 dtex. The tube containing the fibers was cut using a blade to a length

of approximately 3 cm. An illustration of the sample preparation is shown in Figure 3.5.

Figure 3.5 Sample preparation for Washburn adsorption measurement [29]

The prepared sample acts as a porous solid regardless of whether the fibers

themselves are porous or not because capillaries are created between the individual

fibers. Moreover, because of the large number of individual filaments in the sample, the

results are expected to have very little impact from individual filament variations.

3.5.3 Experimental procedure

The prepared fiber bundle is attached to the hook of the tensiometer using a clamp. A

suitable beaker filled with the test liquid is placed in the platform drive system. The

platform automatically raises the beaker containing the liquid until it makes contact with

the fiber bundle. The moment of contact is determined by the sudden increase in mass

as the liquid begins to penetrate the sample. The increase in mass is plotted as a

function of time until complete penetration or saturation is achieved in the pores of the

sample.

3 Experimental 30

Material constant determination

Hexane is used to determine the material constant of the prepared sample. A minimum

of 3 measurements was carried out to determine the average material constant. Figure

3.6 shows the rate of adsorption of hexane in the sample. The initial increase in mass

is when the sample makes contact with the liquid surface. Then there is a steady

increase in mass until the sample reaches its saturation point. The rate of increase in

mass, or adsorption, can be determined from a linear regression of the initial portion

before saturation is reached (where the slope is horizontal).

Contact angle determination

Distilled water with a 72 mN/m surface tension is used to determine the contact angle.

For the PVDF sample, as expected, their slower rate of penetration with water as

compared with hexane because of the higher surface tension. This is shown in Figure

3.6. A minimum of three measurements were carried out per sample.

Surface energy determination

The surface energy can be determined by plotting the contact angle of the sample

against a range of liquids of different surface tensions according to the Zisman method.

Figure 3.6 Rate of adsorption for hexane and water for determination of material

constant and contact angle

3 Experimental 31

3.6 Differential scanning calorimetry

Differential scanning calorimetry (DSC) is an experimental thermoanalytical technique

to measure the heat energy uptake that takes place in a sample during controlled

increase (or decrease) in temperature. The main application of DSC is in studying

phase transitions, such as melting, glass transitions, or exothermic decompositions.

These transitions involve energy changes or heat capacity changes that can be

detected by DSC with great sensitivity.

In a typical DSC experiment the sample specimen is heated at a constant rate in the

sample cell alongside an identical reference cell. Differences in heat energy uptake

between the sample and reference cells required to maintain equal temperature

correspond to differences in apparent heat capacity. The output from any DSC

experiment is a thermogram showing excess heat capacity as a function of

temperature. The heat of fusion or enthalpy is the total integrated area under the

thermogram peak, which, after appropriate baseline correction, represents the total

energy uptake by the sample undergoing the transition. This heat uptake depends on

the amount of sample present in the active volume of the DSC cell, and is in principle a

model-free absolute measure of the absolute enthalpy of the process involved.

The results are heat flow (mW) as a function of the temperature (°C). The degree of

crystallinity Xc (%) in a polymer can be calculated based on the enthalpy ∆H.

∆H = dH

dTdT

T2

T1

Xc ∆H

∆H 100

where ∆H is the measured enthalpy for the sample, and ∆H0 is the theoretical enthalpy

for the pure PVDF crystal (taken as 104.7 J/g [31]).

3.6.1 Interpretation of double endotherms

In many semicrystalline polymers, double endotherms such as multiple peaks or peaks

with ‘shoulders’ are sometimes found in the melting region. The interpretations [32,31]

of this phenomenon are:

1. The lower-temperature endotherm does not correspond to melting of a

crystalline phase, but rather to a solid-solid phase transition or partial melting.

The higher-temperature endotherm indicates melting of the crystalline phase

formed by such transitions as orientation changes of crystals, phase transition

between crystalline modifications, or recrystallization.

2. The two endotherms are attributable to the melting of two different crystalline

phases initially coexisting.

3 Experimental 32

For PVDF with its known polymorphism, the double melting peaks are attributed to the

different crystalline phases. The different phases have different melting temperatures,

though there is no single thermodynamic melting point that has been proposed in

literature for each polymorph of PVDF. This melting point will also vary between

different resins as well as on their respective treatments.

To analyze the double melting peaks, it is necessary to carry out peak separation and

fitting. The Peak Analyzer tool in OriginLab Corporation’s OriginPro 8 (Massachusetts,

USA) was used for peak analysis. The fitted peaks were used to calculate the relative

area of the peaks attributed to melting of the different crystalline phases. The peaks are

identified based on the known melting points of the different crystalline phases, and

accounting for differences in the melting characteristics of different PVDF resins. The

peaks are considered to be Gaussian peaks.

Taking the standard melting point of our particular resin as given by the manufacturer

as 170 °C for the α-phase, we can additionally consider the melting point of the β-

phase at 166 °C [13,33]. The higher melting temperature peak can be attributed to the

γ-phase at 178 °C [15,34]. The γ-phase is usually seen in very small amounts.

3.6.2 Experimental procedure

The PerkinElmer, Inc. (Massachusetts, USA) DSC-7 differential scanning calorimeter is

used to measure the melting temperatures and enthalpies associated with each

crystalline phase of polymer. The temperature is calibrated against a zinc and indium

reference standard, and enthalpy scales are calibrated against an indium reference

standard. A baseline is established before each set of scans using empty perforated

crucibles.

The fiber samples are prepared by cutting the filaments into small lengths of

approximately 2–4 mm, and 6–12 mg of the fibrous mass is placed in aluminum

crucibles, crimped, and perforated. The prepared crucibles are placed in the DSC

furnace.

Thermograms are recorded between 50–250 °C at a heating rate of 10 °C/min under

an inert atmosphere of dry nitrogen as a purge gas at 20 ml/min. The procedure, after

equilibrating at an initial temperature of 50 °C is given below:

1. Hold for 3 minutes at 50 °C.

2. Heat from 50 °C to 250 °C at 10 °C/min.

3. Hold for 1 minute at 250 °C.

4. Cool from 250 °C to 50 °C at 10 °C/min.

5. Hold for 1 minute at 50 °C.

6. Heat from 50 °C to 250 °C at 10 °C/min

3 Experimental 33

3.7 X-ray diffraction

X-ray diffraction (XRD) is an accurate technique for measuring the exact amount of the

different crystalline structures present in the samples. X-ray diffraction was carried out

at the Institut de Chimie des Surfaces et Interfaces (ICSI), Mulhouse, France.

4 Results and discussion 34

4 Results and discussion

All results and discussion are presented for samples V1–V15 with 24 filaments (unless

mentioned otherwise). The spinning parameters for the samples are given in the

Appendix.

4.1 Spinning of PVDF filaments

PVDF was successfully produced as multi-filament yarn from 180-340 dtex. The

average measured diameter of the individual filaments from optical micrographs

(Figure 4.1) is 23.79 and 13.59 micrometers for the 24 filament and 72 filament yarn

specimens, respectively.

Figure 4.1 Optical micrographs for 24 filament (left) and 72 filament (right) yarn

specimens

The production of PVDF filaments by melt-spinning is similar to that of other

thermoplastic polymers. PVDF can be easily produced using a range of processing

conditions. Spinning of 24 and 72 filament yarn was under the same conditions and

with similar results.

At the higher draw temperature of 160 °C the filaments were observed to soften and

even melt at the heated godet roll. This temperature is above the softening point of

145 °C of PVDF, and close to the melting temperature of 170 °C. Higher spin-finish

application was also required otherwise static charging was observed and takeup was

unstable. The maximum drawing temperature is recommended to be below 160 °C for

stable production. However it was still possible to process the PVDF at this

temperature.

Further discussion of the effect of the spinning parameters are in the following sections.

The complete spinning parameters are given in Appendix A.


4.1.1 Spinning of ultrafine filaments

Trials conducted to spin a yarn of finer titer of 90 dtex with the 72 hole spinneret were

not successful. The goal is to achieve a 1.25 dtex per filament titer. At higher spin/draw

ratio (spin pump speed at 25 rpm) there were frequent breakages in the quenching

zone. A variety of process settings was tried with no success. At lower spin/draw ratios

(spin pump speed at 25 rpm) the process was also unstable. Winding could not take

place for more than 5 minutes before breakages were observed at the winder or in the

quenching zone. Only one sample (V31) could be collected.

A possible solution to spin finer filaments is to use a higher viscosity and higher

molecular weight grade of PVDF resin.

4.2 Linear density

The linear density is always in the range as expected from the spinning calculations.

The yarns produced are of 340, 240 and 180 dtex. Additionally, one 90 dtex yarn is

also produced. The linear density results are given in the Appendix with the spinning

parameters.

4.3 Tensile testing

Tensile testing results for PVDF show a viscoelastic stress-strain behavior

characteristic of thermoplastic yarns, with a high initial modulus during elastic

extension, and a yield point followed by inelastic extension. Figure 4.2 for sample V5 is

an example of the typical stress-strain curve from the results.


Figure 4.2 Stress-strain behavior for sample V5 is typical of PVDF fibers

Figure 4.3 and Table 4.1 summarize the strength and elongation results for draw

temperature and draw ratio. Higher draw temperatures shown an increase in strength

and a decrease in elongation. More significant is the effect of the draw ratio, where an

increase in draw ratio shows a significant increase in strength and decrease in

elongation.

The response of PVDF fibers to draw ratio and draw temperature is similar to that of

other thermoplastic polymers. Higher draw ratios and draw temperatures result in

higher strength and lower elongation.

Figure 4.3 Strength and elongation vs. draw temperature and draw ratio for samples

V1–V15


Table 4.1 Tensile testing results for samples V1–V15

ID

Draw

ratio

DR

[°C]

Strength

[cN/tex]

Elongation

[%]

V1 1.0 25 10.34 233.51

V2 1.0 25 12.77 177.49

V3 1.0 25 14.81 124.30

V4 1.5 25 15.31 103.70

V5 1.5 25 23.08 72.53

V6 2.5 25 26.06 54.98

V7 2.5 70 26.84 53.54

V8 2.0 70 22.68 69.74

V9 1.5 70 17.67 97.22

V10 1.5 130 19.44 92.14

V11 2.0 130 23.68 68.60

V12 2.5 130 26.25 42.79

V13 2.5 160 29.26 35.20

V14 2.0 160 24.86 55.94

V15 1.5 160 20.37 79.12

4.4 Wetting and surface energy

4.4.1 Contact angle and material constant determination

The effect of the draw ratio and draw temperature on the contact angle is shown in

Figure 4.4 – there is no notable trend from either. The high standard deviation should

be noted in the contact angle results. The average value of contact angle is 75.28°,

which is in agreement with values found in literature [35].


Figure 4.4 Contact angle vs. draw ratio and draw temperature for samples V1–V15

A high standard deviation is also seen in the measurements for the material constants,

given in Table 4.2. According to literature the standard deviation for the material

constant using a fully wetting liquid such as hexane should be precise to 2 significant

figures across samples [29]. The results for PVDF show a much higher variation.

Possible reasons are operator error, instrument error, or simply a high variation across

samples.

4.4.2 Surface energy determination

Further experiments to determine surface energy were not carried out because of the

high deviation in the experimental data. Values for surface energy from literature are

28–32.70 mN/m [36]. The KRÜSS website gives four values of surface energy for

PVDF, 25.00, 32.10, 32.28 and 32.70 mN/m. DataPhysics Instruments GmbH

(Filderstadt, Germany) gives the surface free energy of PVDF at 30.3 mN/m, with a

23.3 mN/m and 7 mN/m for dispersive and polar contribution respectively. The values

for surface energy are different depending on the method of calculation used, so there

is a representative range rather than a single value.

4.4.3 Conclusion

The results for the material constant and contact angle values are given in Table 4.2,

including number of experiments (n), standard deviation (SD) and coefficient of

variation (CV). Because the contact angles results between the samples are

statistically similar, it can be concluded that there is no significant effect on surface

properties. However, another conclusion that can be made is that the different material

constants are due to differences in the pore characteristics (namely the size and

possibly the number of pores). The evenness of the spin-finish application also

contributes to the variation in the results. Certain samples exhibited a high amount of

static charging, which is indicative of too low or un-even spin-finish application.


Table 4.2 Material constant and contact angle values

ID

Material

constant

[10-2.cm-5] N SD CV

Contact

angle

[°] N SD CV

V1 5.71E-07 4 5.87E-08 0.10 74.90 3 9.15 0.12

V2 2.61E-07 4 4.81E-08 0.18 72.25 3 8.51 0.12

V3 2.74E-07 6 7.96E-08 0.29 77.47 6 4.02 0.05

V4 0.95E-07 7 1.03E-07 1.09 65.21 5 12.90 0.20

V5 1.78E-07 6 3.21E-08 0.18 72.94 3 7.45 0.10

V6 1.88E-07 6 5.29E-08 0.28 76.41 7 9.81 0.13

V7 2.05E-07 6 3.91E-08 0.19 79.85 7 3.62 0.05

V8 2.01E-07 4 6.47E-08 0.32 85.09 5 2.38 0.03

V9 0.89E-07 3 5.23E-08 0.59 54.91 3 19.39 0.35

V10 1.79E-07 4 1.80E-08 0.10 77.63 4 3.56 0.05

V11 1.96E-07 4 4.55E-08 0.23 79.18 6 3.67 0.05

V12 2.46E-07 5 4.94E-08 0.20 79.39 3 2.39 0.03

V13 1.99E-07 6 5.39E-08 0.27 77.49 7 3.31 0.04

V14 2.53E-07 5 6.67E-08 0.26 80.61 3 4.06 0.05

V15 3.15E-07 6 1.05E-07 0.34 75.89 4 7.19 0.09


4.5 Differential scanning calorimetry

4.5.1 1st heating scan

The first heating scans give an equilibrium melting peak temperature of 170.93 °C (SD

1.06), enthalpy of 44.37 J/g (SD 5.54) and a degree of crystallinity of 43 % (SD 5.19).

The results are summarized in Table 4.3. The heating scans are given in Figure 4.5,

showing a broad melting peak. A smaller higher-temperature peak can be seen at

177.99 °C (SD 0.63) contributing 0.09–2.37 % to the total crystallinity. This smaller

peak is attributed to the γ-phase. Specimens V6–V8 and V12–V14 have multiple peaks

or shoulders within the broad melting peaks, attributed to the existence of multiple

crystalline phases. A further discussion follows in Section 4.5.4 on polymorphism.

Figure 4.5 DSC thermograms for the 1st heating scan


Table 4.3 DSC results for 1st heating scan

Primary peak Secondary peak

ID DR DT

Peak α

[°C]

Peak

β [°C]

Peak

[°C] ∆H Xc

Peak

γ [°C] ∆H Xc

Total

Xc

V1 1 25 170.87 – – 45.39 43.35 177.53 0.11 0.11 43.46

V2 1 25 171.53 – – 44.87 42.86 178.20 0.16 0.15 43.01

V3 1 25 171.37 – – 42.54 40.63 178.03 0.09 0.09 40.72

V4 1.5 25 171.03 – – 47.16 45.04 177.20 0.18 0.17 45.22

V5 2 25 171.03 – – 48.99 46.79 177.53 2.48 2.37 49.15

V6 2.5 25 170.20 164.10 – 49.84 47.61 178.20 0.95 0.91 48.51

V7 2.5 70 168.87 164.31 171.42 52.02 49.68 177.87 0.50 0.47 50.16

V8 2 70 172.37 169.75 – 30.50 29.13 179.20 2.11 2.01 31.14

V9 1.5 70 171.53 – – 43.84 41.87 – – – 41.87

V10 1.5 130 170.20 – – 41.74 39.86 176.87 1.06 1.01 40.87

V11 2 130 172.37 – – 38.43 36.70 178.87 0.61 0.59 37.29

V12 2.5 130 170.53 165.15 – 45.45 43.41 178.03 0.34 0.32 43.73

V15 1.5 160 170.87 – – 45.01 42.99 177.53 0.53 0.51 43.50

V14 2 160 172.20 165.15 – 38.96 37.21 178.53 0.16 0.15 37.36

V13 2.5 160 169.03 165.36 – 50.83 48.55 178.20 0.45 0.43 48.98


Figure 4.6 DSC thermograms for the cooling scan and 2nd heating scan

4.5.2 Cooling scan and 2nd heating scan

The cooling scans shown in Figure 4.6 are consistent across the samples. The average

recrystallization peak is as expected [35] at 141.94 °C with a 53.61 J/g enthalpy.

The second heating scans shown in Figure 4.6 exhibit a single broad melting peak,

showing that the crystalline structures imparted during processing have been removed.

The equilibirium melting peak is at 169.86 °C with a 45.13 % degree of crystallinity and

47.25 J/g enthalpy.

Table 4.4 summarizes the results for melting peak, enthalpy ∆H and degree of

crystallinity Xc for the cooling scan and the 2nd heating scan.


Table 4.4 DSC results for the cooling and 2nd heating scan

Cooling scan 2nd heating scan

ID DR DT °C ∆H Xc °C ∆H Xc

V1 1.0 25 141.30 52.23 49.88 169.37 51.62 49.30

V2 1.0 25 141.47 53.16 50.77 170.70 40.73 38.90

V3 1.0 25 142.13 51.07 48.78 170.20 44.65 42.65

V4 1.5 25 141.30 55.04 52.57 169.70 47.16 45.04

V5 2.0 25 141.30 56.67 54.12 168.70 51.37 49.06

V6 2.5 25 142.47 53.10 50.72 170.20 53.81 51.40

V7 2.5 70 142.47 56.23 53.70 170.03 54.54 52.09

V8 2.0 70 142.63 52.87 50.50 170.53 45.05 43.03

V9 1.5 70 142.30 53.63 51.23 170.20 50.68 48.41

V10 1.5 130 140.30 51.57 49.26 168.70 40.71 38.88

V11 2.0 130 142.30 53.81 51.39 170.53 45.16 43.13

V12 2.5 130 142.63 58.59 55.96 170.53 46.62 44.53

V13 2.5 160 142.27 52.08 49.74 170.03 45.94 43.87

V14 2.0 160 142.63 49.87 47.64 169.70 42.70 40.78

V15 1.5 160 141.63 54.17 51.74 168.70 48.06 45.90

4.5.3 Polymorphism

Multiple endotherms or shoulders in the 1st heating scan indicate polymorphism. Curve

fitting as described in Section 3.6.1 give the results for samples V6–V8 in Error! Ref-

erence source not found. and for V12–V14 Error! Reference source not found.

with the with Gaussian-fit curves (dashed line) for primary peak area and individual

peak-fit curves. The results are summarized in Figure 4.7. Increasing draw ratio and

draw temperature show a clear trend in an increase in the β-phase.


Figure 4.7 Degree of crystallinity vs. draw temperature and draw ratio of the α- and β-

phase according to curve fitting on DSC thermograms

4.5.4 Conclusion

The DSC results for degree of crystallinity vs. draw ratio and draw temperature are

summarized in Figure 4.8. The effect of degree of crystallinity from different draw

temperatures does not show a significant trend. However, the draw ratio does have a

notable effect. At ambient temperature drawing, the degree of crystallinity increases

with increasing drawing, with the optimal draw ratio at 2.0. At elevated temperatures,

there is a decrease in the degree of crystallinity at a draw ratio of 2.0, followed by a

significant increase at the higher draw ratio of 2.5. The 70 °C drawing temperature

shows the most significant drop in crystallinity at a draw ratio of 2.0, and the highest

crystallinity at a draw ratio of 2.5.

Considering the DSC results with the tensile testing results, the strength is affected by

the higher degree of orientation rather than the changes in level of crystallinity.

Figure 4.8 Degree of crystallinity vs. draw ratio and draw temperature according to

DSC results


Figure 4.9 DSC thermograms for samples V6–V8 with Gaussian-fit curves


Figure 4.10 DSC thermograms for samples V12–V14 with Gaussian-fit curves


4.6 X-ray diffraction

X-ray diffraction was carried out by Dr. Dimitri A. Ivanov at the Institut de Chimie des

Surfaces et Interfaces (ICSI), Mulhouse, France on three samples V9, V12 and V13.

Preliminary analysis of x-ray diffraction results showed that there is almost only β-

phase in sample V9 (Figure 4.11), mixture of α- and β-phase in V12 (Figure 4.12) and

pure α-phase in V13 (Figure 4.13).

This is consistent with our expected results from literature on phase transformations of

PVDF. Sample V9 was drawn at 70 °C, and in spite of the relatively low draw ratio

there is excellent α β transformation. At a higher draw temperature of 130 °C in

sample V12 the β-phase can be attributed to the higher draw ratio of 2.5. Finally, at the

even higher draw temperature of 160 °C but the same draw ratio of 2.5, the β-phase

completely disappears in favor of the more stable α-phase which crystallizes closer to

the melting temperature.

Figure 4.11 X-ray diffractogram for PVDF V9 shows mostly β-phase


Figure 4.12 X-ray diffractogram for PVDF V12 shows a mixture of α- and β-phase

Figure 4.13 X-ray diffractogram for PVDF V13 shows pure α-phase


4.7 Comparison of XRD and DSC results

Comparing the XRD results to the DSC results, Sample V9 shows a single melting

peak at 171.53 °C which is generally attributed to the α-phase. However, considering

the XRD results and the melting temperature of the polymer, we can conclude that this

melting peak is of a single crystalline phase, and that is the β-phase. Additionally, there

is no presence of the γ-phase in the DSC results for sample V9, and thus the 70 °C

draw temperature resulted in only β-phase crystallization.

Sample V12 shows a mixture of α- and β-phase in both DSC and XRD results.

In the DSC results sample V13 exhibits a significant lower temperature shoulder at

165.36 °C which is attributed to the β-phase. This can be re-interpreted as partial

melting in the crystalline regions due to the higher level of crystalline orientation from

the higher draw ratio of 2.5.

5 Conclusion 50

5 Conclusion

In the scope of this project PVDF multi-filament yarn is successfully produced from

340–180 dtex with 24 and 72 filaments at different draw ratios and draw temperatures.

90 dtex yarn was also produced, but the production was too unstable to be called a

success.

The spinning parameters resulted in different crystalline structures. The main

crystalline structures, α-, β- and γ-phase are achieved by varying the draw

temperature. This is the first project to achieve different crystalline phases of PVDF in

yarns through in-line drawing.

The drawing temperature is the significant control parameter for the different crystalline

structures. Draw temperatures of 70 °C resulted in the highest β-phase. Higher draw

ratios also favor the formation of the β-phase, though this decreases in favor of the α-

phase at the higher draw temperatures.

PVDF exhibits tensile curves similar to that of other semicrystalline polymers, and is

well suited for biomedical applications. Higher draw ratios and draw temperatures

result in higher strength and lower elongation.

Characterization of the PVDF by wetting and surface energy determination did not yield

useful results – the high standard deviation contact angle measurement methods is

also a factor. DSC scans show that the degree of crystalline increase with increasing

draw ratios. The presence of multiple crystalline phases is revealed in the DSC results.

X-ray diffraction results good results. However XRD was carried out only for three

samples.

The literature review revealed that PVDF has a promising future in biomedical

applications, and detailed characterization of the material will help in selecting optimal

properties

5.1 Future scope

Additional characterization should be carried out after preliminary results from cell-

seeding. Cell-seeding results should aid in selecting yarns for further characterization.

The most significant analytical method for crystalline morphology is x-ray diffraction,

and this method should be the focus of further characterization.

Surface energy can be evaluated using a sample holder for staple fibers.

To produce finer titer filaments of < 1.5 dpf, a lower viscosity and higher molecular

weight PVDF resin should be used. One such resin is the Solef 1008 PVDF resin from

Solvay Solexis.

5 Conclusion 51

It is interesting to see if the piezoelectric form of PVDF has an effect on biomedical

applications. The yarn can be poled in-line during the draw phase, or in a subsequent

process. Poled and un-poled yarns should be evaluated by cell-seeding. The

piezoelectric properties should be additionally evaluated.

One paper mentions that the addition of blue tint to PVDF sutures results in a higher β-

phase. The pigment acts as an additive that increases the monomer inversions

resulting in a higher β-phase formation. Colored PVDF yarns should be evaluated, as

well as the effect of other additions to the polymer blend for example a small amount of

polypropylene (which requires similar processing temperatures.

6 Bibliography 52

6 Bibliography

[1] H. Kawai, “The Piezoelectricity of Poly(vinylidene Fluoride),” Japan Journal of Applied Physics, vol. 8, Jul. 1969, pp. 975-976.

[2] T.A. Ford and W.E. Hanford, “United States Patent: 2435537 - Polyvinylidene Fluoride and process for obtaining the same,” Feb. 1948.

[3] R.J. Plunkett, “United States Patent: 2230654 - Tetrafluoroethylene polymers,” Feb. 1941.

[4] E. Fukada, “Piezoelectricity as a fundamental property of wood,” Wood Science and Technology, vol. 2, Dec. 1968, pp. 299-307.

[5] E. Fukada, “History and recent progress in piezoelectric polymers,” Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on, vol. 47, 2000, pp. 1277-1290.

[6] D. Rhees, “Electricity-'the greatest of all doctors": an introduction to "high frequency oscillators for electro-therapeutic and other purposes",” Proceedings of the IEEE, vol. 87, 1999, pp. 1277-1281.

[7] L. Rosner, “The professional context of electrotherapeutics,” Journal of the History of Medicine and Allied Sciences, vol. 43, Jan. 1988, pp. 64-82.

[8] J. Bergman, J.H. McFee, and G.R. Crane, “Pyroelectricity and optical second harmonic generation in polyvinylidene flouride films,” Applied Physics Letters, vol. 18, Mar. 1971, pp. 203-205.

[9] A.M. Glass, J.H. McFee, and J. Bergman, “Pyroelectric Properties of Polyvinylidene Flouride and Its Use for Infrared Detection,” Journal of Applied Physics, vol. 42, Dec. 1971, pp. 5219-5222.

[10] J.H. McFee, J.G. Bergman, and G.R. Crane, “Pyroelectric and nonlinear optical properties of poled polyvinylidene fluoride films,” Ferroelectrics, vol. 3, 1972, p. 305.

[11] T. Furukawa, M. Date, and E. Fukada, “Hysteresis phenomena in polyvinylidene fluoride under high electric field,” Journal of Applied Physics, vol. 51, Feb. 1980, pp. 1135-1141.

[12] R.G. Kepler and R.A. Anderson, “Ferroelectric polymers,” Advances in Physics, vol. 41, 1992, pp. 1 - 57.

[13] A.J. Lovinger, “Poly(vinylidene flouride),” Developments in Crystalline Polymers, Applied Science Publishers, 1982, pp. 195-273.

[14] B.L. Farmer, A.J. Hopfinger, and J.B. Lando, “Polymorphism of poly(vinylidene fluoride): potential energy calculations of the effects of head-to-head units on the chain conformation and packing of poly(vinylidene fluoride),” Journal of Applied Physics, vol. 43, Nov. 1972, pp. 4293-4303.

[15] S. Osaki and T. Kotaka, “Electrical properties of form III - poly(vinylidene fluoride),” Ferroelectrics, vol. 32, 1981, p. 1.

[16] C. Du, B. Zhu, and Y. Xu, “Effects of stretching on crystalline phase structure and morphology of hard elastic PVDF fibers,” Journal of Applied Polymer Science, vol. 104, 2007, pp. 2254-2259.

6 Bibliography 53

[17] R. Gregorio, Jr, and M. Cestari, “Effect of crystallization temperature on the crystalline phase content and morphology of poly(vinylidene fluoride),” Journal of Polymer Science Part B: Polymer Physics, vol. 32, 1994, pp. 859-870.

[18] P. Sajkiewicz, A. Wasiak, and Z. Goclowski, “Phase transitions during stretching of poly(vinylidene fluoride),” European Polymer Journal, vol. 35, Mar. 1999, pp. 423-429.

[19] C.C. Hsu and P.H. Geil, “Morphology-structure-property relationships in ultraquenched poly(vinylidene fluoride),” Journal of Applied Physics, vol. 56, Nov. 1984, pp. 2404-2411.

[20] D. Song, D. Yang, and Z. Feng, “Formation of β-phase microcrystals from the melt of PVF2-PMMA blends induced by quenching,” Journal of Materials Science, vol. 25, Jan. 1990, pp. 57-64.

[21] C. Hung, Y. Lin, and T. Young, “The effect of chitosan and PVDF substrates on the behavior of embryonic rat cerebral cortical stem cells,” Biomaterials, vol. 27, Sep. 2006, pp. 4461-4469.

[22] G. Laroche et al., “Polyvinylidene fluoride (PVDF) as a biomaterial: From polymeric raw material to monofilament vascular suture,” Journal of Biomedical Materials Research, vol. 29, 1995, pp. 1525-1536.

[23] U. Klinge et al., “PVDF as a new polymer for the construction of surgical meshes,” Biomaterials, vol. 23, Aug. 2002, pp. 3487-3493.

[24] J. D'Agnese, “Tissue Engineering,” DISCOVER Magazine, Oct. 2005; http://discovermagazine.com/2005/oct/tissue-engineering.

[25] ISO, Textiles -- Yarns from packages -- Determination of single-end breaking force and elongation at break, ISO - International Organization for Standardization, 1993

[26] U. Ohlerich, “Surface characterization in biomedical engineering,” 1996.

[27] Wikipedia contributors, “Wetting,” Wikipedia, The Free Encyclopedia, Wikimedia Foundation, 2008

[28] T. Young, “An Essay on the Cohesion of Fluids,” Philosophical Transactions of the Royal Society of London (1776-1886), vol. 95, Jan. 1805, pp. 65-87.

[29] C. Rulison, “Contact Angle Determination by the "Straw" Method and Packed Cell Method,” 1996.

[30] E.W. Washburn, “The Dynamics of Capillary Flow,” Physical Review, vol. 17, Mar. 1921, p. 273.

[31] K. Nakagawa and Y. Ishida, “Annealing effects in poly(vinylidene fluoride) as revealed by specific volume measurements, differential scanning calorimetry, and electron microscopy,” Journal of Polymer Science: Polymer Physics Edition, vol. 11, 1973, pp. 2153-2171.

[32] N.A. Hakeem et al., “Spectroscopic, thermal, and electrical investigations of PVDF films filled with BiCl3,” Journal of Applied Polymer Science, vol. 102, 2006, pp. 2125-2131.

[33] V. Sencadas, S. Lanceros-Mendez, and J.F. Mano, “Characterization of poled and

non-poled [beta]-PVDF films using thermal analysis techniques,” Thermochimica Acta, vol. 424, Dec. 2004, pp. 201-207.

6 Bibliography 54

[34] S. Osaki and Y. Ishida, “Effects of annealing and isothermal crystallization upon crystalline forms of poly(vinylidene fluoride),” Journal of Polymer Science: Polymer Physics Edition, vol. 13, 1975, pp. 1071-1083.

[35] Solvay Solexis, “Solef & Hylar Polyvinylidene fluoride Design and Processing Guide,” 2006.

[36] P.G. de Gennes, “Wetting: statics and dynamics,” Reviews of Modern Physics, vol. 57, Jul. 1985, p. 827.

7 Appendix 55

7 Appendix

Data for the spinning parameters for the yarns produced is presented in the following

pages 56–58.

7 Appendix 56

Sam

ple

Id.

dte

x (t

arg

et)

dte

x (e

xpec

ted

)

dte

x (a

ctu

al)

Dra

w r

atio

To

tal t

hro

ug

hp

ut

[g/m

in]

Sp

inn

eret

vel

oci

ty

[m/m

in]

Sp

in/d

raw

rat

io

Dra

w t

emp

erat

ure

[°C

]

Sp

inn

eret

Sp

in p

um

p s

pee

d

[rp

m]

Qu

ench

air

flo

w [

m/s

]

Qu

ench

air

tem

per

a-

ture

[°C

]

Sp

in f

inis

h d

osa

ge

[rp

m]

DU

O s

pee

d [

m/m

in]

MO

NO

1 s

pee

d

[m/m

in]

MO

NO

1 T

emp

erat

ure

[°C

]

MO

NO

2 s

pee

d

[m/m

in]

MO

NO

2 T

emp

erat

ure

[°C

]

Win

der

tra

vers

e

[m/m

in]

Win

der

fri

ctio

n r

oll

[m/m

in]

V1 340 342 333.77 1.0 23.3 4.3 157 27 B 25 0.3 23.1 35 680 700 27.1 730 26.4 500 680

V2 240 240 235.95 1.0 23.3 4.3 224 28 B 25 0.3 22.6 35 970 1000 27.7 1030 26.8 700 970

V3 180 180 175.16 1.0 23.3 4.3 298 27 B 25 0.3 22.4 35 1290 1330 27.3 1380 26.9 1000 1290

V4 180 180 181.76 1.5 23.3 4.3 198 30 B 25 0.3 24.3 50 860 1420 29.7 1480 28.9 1000 1290

V5 180 180 176.65 2.0 23.3 4.3 149 30 B 25 0.3 23.7 50 645 1420 30.2 1480 29.6 1000 1290

V6 180 180 187.2 2.5 23.3 4.3 119 30 B 25 0.3 24.5 50 516 1420 30.3 1455 29.4 1000 1290

V7 180 180 175.82 2.5 23.3 4.3 119 70 B 25 0.3 23.3 50 516 1420 70 1450 55 1000 1290

V8 180 180 177.87 2.0 23.3 4.3 149 70 B 25 0.3 24.2 50 645 1420 70 1450 55 1000 1290

V9 180 180 180.22 1.5 23.3 4.3 198 70 B 25 0.3 23.2 50 860 1420 70 1480 55 1000 1290

V10 180 180 180.25 1.5 23.3 4.3 198 130 B 25 0.3 23 50 860 1340 130 1365 55 1000 1290

V11 180 180 178.73 2.0 23.3 4.3 149 130 B 25 0.3 23.9 50 645 1340 130 1365 55 1000 1290

V12 180 180 178.48 2.5 23.3 4.3 119 130 B 25 0.3 23.8 50 516 1340 130 1375 55 1000 1290

V13 180 180 176.51 2.5 23.3 4.3 119 160 B 25 0.3 23.6 50 516 1340 160 1360 55 1000 1290

V14 180 180 178.02 2.0 23.3 4.3 149 160 B 25 0.3 24.8 50 645 1335 160 1350 55 1000 1290

7 Appendix 57

Sam

ple

Id.

dte

x (t

arg

et)

dte

x (e

xpec

ted

)

dte

x (a

ctu

al)

Dra

w r

atio

To

tal t

hro

ug

hp

ut

[g/m

in]

Sp

inn

eret

vel

oci

ty

[m/m

in]

Sp

in/d

raw

rat

io

Dra

w t

emp

erat

ure

[°C

]

Sp

inn

eret

Sp

in p

um

p s

pee

d

[rp

m]

Qu

ench

air

flo

w [

m/s

]

Qu

ench

air

tem

per

a-

ture

[°C

]

Sp

in f

inis

h d

osa

ge

[rp

m]

DU

O s

pee

d [

m/m

in]

MO

NO

1 s

pee

d

[m/m

in]

MO

NO

1 T

emp

erat

ure

[°C

]

MO

NO

2 s

pee

d

[m/m

in]

MO

NO

2 T

emp

erat

ure

[°C

]

Win

der

tra

vers

e

[m/m

in]

Win

der

fri

ctio

n r

oll

[m/m

in]

V15 180 180 177.61 1.5 23.3 4.3 198 160 B 25 0.3 23.2 50 860 1335 160 1350 55 1000 1290

V16 340 341 328.5 1.0 14.0 8.2 51 24 A 15 0.45 21.7 25 417 427 23.8 437 22.3 309.2 410

V17 240 241 232.23 1.0 14.0 8.2 71 23 A 15 0.45 21.8 25 585 595 23.4 605 22.1 400 580

V18 180 180 173.98 1.0 14.0 8.2 95 23 A 15 0.45 21.4 25 780 790 23.4 800 22.1 506.3 775

V19 180 180 177.44 1.5 14.0 8.2 63 34 A 15 0.45 20.5 45 520 785.3 34 890 28.6 790 775

V20 180 180 174.42 2.0 14.0 8.2 48 27 A 15 0.45 21.2 45 390 675 26.9 900 24.5 883.5 775

V21 180 180 176.06 2.5 14.0 8.2 38 26 A 15 0.45 22 15 310 600 26 870 25 600 775

V22 180 180 176.75 1.5 14.0 8.2 63 70 A 15 0.45 20.8 45 520 785.3 70 890 55 660 775

V23 180 180 173.52 2.0 14.0 8.2 48 70 A 15 0.45 21.2 45 390 675 70 890 55 660 775

V24 180 180 174.51 2.5 14.0 8.2 38 70 A 15 0.45 21.8 45 310 600 70 850 55 660 775

V25 180 180 172.49 1.5 14.0 8.2 63 130 A 15 0.45 21.8 45 520 785.3 130 850 55 660 775

V26 180 180 176.19 2.0 14.0 8.2 48 130 A 15 0.45 20.2 45 390 675 130 850 55 660 775

V27 180 180 174.86 2.5 14.0 8.2 38 130 A 15 0.45 20.6 45 310 600 130 860 55 660 775

V28 180 180 177.57 1.5 14.0 8.2 63 160 A 15 0.45 21.6 65 520 785.3 160 850 55 660 775

7 Appendix 58

Sam

ple

Id.

dte

x (t

arg

et)

dte

x (e

xpec

ted

)

dte

x (a

ctu

al)

Dra

w r

atio

To

tal t

hro

ug

hp

ut

[g/m

in]

Sp

inn

eret

vel

oci

ty

[m/m

in]

Sp

in/d

raw

rat

io

Dra

w t

emp

erat

ure

[°C

]

Sp

inn

eret

Sp

in p

um

p s

pee

d

[rp

m]

Qu

ench

air

flo

w [

m/s

]

Qu

ench

air

tem

per

a-

ture

[°C

]

Sp

in f

inis

h d

osa

ge

[rp

m]

DU

O s

pee

d [

m/m

in]

MO

NO

1 s

pee

d

[m/m

in]

MO

NO

1 T

emp

erat

ure

[°C

]

MO

NO

2 s

pee

d

[m/m

in]

MO

NO

2 T

emp

erat

ure

[°C

]

Win

der

tra

vers

e

[m/m

in]

Win

der

fri

ctio

n r

oll

[m/m

in]

V29 180 180 177.98 2.0 14.0 8.2 48 160 A 15 0.45 20.8 65 390 675 160 845 55 660 775

V30 180 180 174.45 2.5 14.0 8.2 38 160 A 15 0.45 21.6 45 310 600 160 850 55 660 775

V31 90 93 93.5 1.4 14.0 8.2 127 80 A 15 0.45 20.8 45 1043.8 1309.3 80 1670 55 1006 1500

8 Declaration 59

8 Declaration

Hereby I declare that the presented Master thesis has been completed by me

independently. The sources of support mentioned have been utilized for the work

carried out. All the knowledge gained in the process of working on the project has been

documented in this thesis.

Place, Date Signature

Rheinisch - Westfälische Technische Hochschule

Aachen

Institut für Textiltechnik der RWTH Aachen

Prof. Dr.-Ing. Dipl.-Wirt. Ing. Thomas Gries

Fakultät für Maschinenwesen

Diplomarbeit Vorgelegt als:

von:

Diese Arbeit ist nur zum internen Gebrauch bestimmt. Alle Urheberrechte liegen beim Institut

für Textiltechnik der RWTH Aachen. Für den Inhalt wird keine Gewähr übernommen.

Betreuende Assistentin:

Aachen, August 2008

Dipl.-Ing. Stéphanie Houis


Matr.-Nr.: 285005

Abid Omar

Masterarbeit

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