European Plastic Welder Chapter 1: Plastics Co – ASR, Romanian Welding Society P1 – CWS, Czech Welding Society ANB P2 – SLV, Schweisstechnische Lehr- und

European Plastic Welder

Chapter 1: Plastics

Co – ASR, Romanian Welding SocietyP1 – CWS, Czech Welding Society ANBP2 – SLV, Schweisstechnische Lehr- und Versuchsanstalt SLV Duisvurg, Niederlassung der GSI mbHP3 – IIS, Italian Welding InstituteP4 – EWF, European Federation for Welding, Joining and CuttingP5 – ISQ, Institute for Welding and Quality

Implementation of European Guidelines for Joining Technology Training, Project no.:2009-1-LEO05-03591


Generals on Polymers

1.1

DefinitionsApplication of polymersNomenclature of polymersClassification of polymersMain physical properties of polymers

Introduction to polymers

Term “polymer”: greek poli (many) + meros (unit) = many units


Polymers are a large class of materials consisting of many small molecules (called monomers) that can be linked together to form long chains, thus they are known as macromolecules (term introduced by H. Staudinger in 1920’s).

A typical polymer may include tens of thousands of monomers. Because of their large size, polymers are classified as macromolecules.

Polymers occur naturally in the form of proteins, cellulose(plants), starch(food) and natural rubber.

Engineering polymers, however, are usually synthetic polymers.

Polymer Large molecule consisting of a number of repeating units with molecularweight typically several thousand or higher

Repeating unitThe fundamental recurring unit of a polymer

MonomerThe smaller molecule(s) that are used to prepare a polymer

OligomerA molecule consisting of reaction of several repeat units of a monomer but not large enough to be consider a polymer

Single repeat unit: MONOMERSingle repeat unit: MONOMERMany repeat units: POLYMERMany repeat units: POLYMER

Degree of polymerizationThe number of the repeating units

Definitions


The field of synthetic polymers or plastics is currently one of the fastest growing materials industries. The interest in engineering polymers is driven by their manufacturability, recyclability, mechanical properties, and lower cost as compared to many alloys and ceramics.

Also the macromolecular structure of synthetic polymers provides good biocompatibility and allows them to perform many biomimetic tasks that cannot be performed by other synthetic materials, which include drug delivery, use as grafts for arteries and veins and use in artificial tendons, ligaments and joints.

Application of polymers



INCPEN, Towards greener households, June 2001 p. 580.0400 A of the Chemical Economics Handbook


ACCENTURE RESEARCH, Trends in Manufacturing Polymers: Achieving High Performance in a Multi-Polar World, www.accenture.com



Nomenclature of polymer

1 -Nomenclature Based on monomer source The addition polymer is often named according to the monomer that was used to form it Example : poly( vinyl chloride ) PVC is made from vinyl chloride

- CH2-CH(Cl)-

If “ X “ is a single word the name of polymer is written out directly

ex. polystyrene -CH2-CH(Ph) -

Poly-X

If “ X “ consists of two or more words parentheses should be used

ex , poly (vinyl acetate ) -CH2-CH(OCOCH3) -

2 -Based on polymer structureThe most common method for condensation polymers since the polymer

contains different functional groups than the monomerImplementation of European Guidelines for Joining Technology Training,

Project no.:2009-1-LEO05-03591

Nomenclature of polymers

PC = PolycarbonatPPE = PolyphenyletherSMA = Styrol-MaleinsäureanhydridABS = Acrylnitril-Butadien-StyrolPMMA = PolymethylmethacrylatPS = PolystyrolSAN = Styrol-Acrylnitril-CopolymerePVC = PolyvinylchloridPET = Polyethylenterephthalat (PETP)PBT = Polybutylenterephthalat (PBTP)PA = PolyamidPOM = PolyoxymethylenRF-PP = Resorcin-Formaldehyd-PolypropylenPE-UHMW = Polyethylen-ultra high molecular weightPP = PolypropylenPE-HD = Polyethylen hoher Dichte (High Density)PE-LD = Polyethylen niedriger Dichte (Low Density)


Classification of polymers

A. Classification by Origin

Synthetic organic polymersBiopolymers (proteins, polypeptides, polynucleotide, polysaccharides, natural rubber)Semi-synthetic polymers (chemically modified synthetic polymers)Inorganic polymers (siloxanes, silanes, phosphazenes)

Main classifications of the polymers:• by origin• by Monomer composition• by chain structure• by thermal behaviour• by kynetics or mechanism• by application


HomopolymersConsist of only one type of constitutional repeating unit (A)

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B. Classification by Monomer Composition

Homopolymers

Copolymers BlockGraftAlternatingStatistical

Homopolymer


Several classes of copolymer are possible Statistical copolymer (Random) ABAABABBBAABAABB two or more different repeating unit are distributed randomly Alternating copolymer ABABABABABABABAB are made of alternating sequences of the different monomers Block copolymer AAAAAAAAABBBBBBBBB long sequences of a monomer are followed

by long sequences of another monomer Graft copolymer AAAAAAAAAAAAAAAAAA B B B B B B Consist of a chain made from one type of

monomers with branches of another type

Copolymers Consist of two or more constitutional repeating units (A-B )

Statistical

Alternating

Block

Graft


c. Classification by Chain structure (molecular architecture)

Linear chains :a polymer consisting of a single continuous chain of repeat units Branched chains :a polymer that includes side chains of repeat units connecting onto the main chain of repeat units Hyper branched polymer consist of a constitutional repeating unit including a branching groups Cross linked polymer :a polymer that includes interconnections between chains Net work polymer :a cross linked polymer that includes numerous interconnections between chains

Linear Branched Cross-linked Network

Direction of increasing strength


d. Classification by Thermal Behavior

Polymers may be classified as follows, according to the mechanical response at elevated temperatures:

• Thermoplasts • Thermosets. a) Thermoplasts: Thermoset polymers soften when heated and harden when cooled. Simultaneous

application of heat and pressure is required to fabricate these materials. On the molecular level, when the temperature is raised, secondary bonding forces

are diminished so that the relative movement of adjacent chains is facilitated when a stress is applied.

Most Linear polymers and those having branched structures with flexible chains are thermoplastics.

Thermoplastics are very soft and ductile. The commercial available thermoplasts are • Polyvinyl Chloride (PVC) and Polystyrene • Polymethyl methacrylate • Polystyrene


Classification by Thermal Behavior

b) Thermosets: Thermosetting polymers become soft during their first heating and become

permanently hard when cooled. They do not soften during subsequent heating. Hence, they cannot be remolded/reshaped by subsequent heating.

In thermosets, during the initial heating, covalent cross-links are formed between adjacent molecular chain. These bonds anchor the chains together to resist the vibration and rotational chain motions at high temperatures. Cross linking is usually extensive in that 10 to 15% of the chain mer units are cross linked. Only heating to excessive temperatures will cause severance of these crosslink bonds and polymer degradation. Thermoset polymers are harder, stronger, more brittle than thermoplastics and have better dimensional stability.

They are more usable in processes requiring high temperatures Most of the cross linked and network polymers which include

• Vulcanized rubbers • Epoxies • Phenolic • Polyester resins

are thermosetting polymers. Thermosets cannot be recycled, do not melt, are usable at higher temperatures

than thermoplastics, and are more chemically inert Implementation of European Guidelines for Joining Technology Training,


f. Classification by Application Plastics Fibers Elastomers Coatings Adhesives

e. Classification Based on Kinetics or Mechanism

Step-growth Chain-growth


1-Primary bonds : the covalent bonds that connect the atoms of the main chain

2 -Secondary bonds : non – covalent bonds that hold one polymer chain to

another including hydrogen bond and other dipole –dipole attraction

3-Crystalline polymer : solid polymers with high degree of structural order and rigidity

4 -Amorphous polymers : polymers with a low degree of structural order

5-Semi – crystalline polymer : most polymers actually consist of both

crystalline domains and amorphous domains with properties between that

expected for a purely crystalline or purely amorphous polymer

6-Glass: the solid form of an amorphous polymer characterized by rigidity and brittleness7 – Crystalline melting temperature (Tm): temperature at which crystalline polymers melt

Main physical properties of polymers

8 - Glass transition temperature (Tg ) : temperature at which an amorphous polymer converts to a liquid or amorphous domains of a semi crystalline polymer melt9 – Thermoplastics (plastics( :polymers that undergo thermally reversible Interconversion between the solid state and the liquid state 10- Thermosets : polymers that continue reacted at elevated temperaturesgenerating increasing number of crosslinks such polymers do not exhibitmelting or glass transition11- Liquid – crystalline polymers : polymers with a fluid phase that retainssome order12- Elastomers : rubbery , stretchy polymers the effect is caused by light crosslinking that pulls the chains back to their original state


Amorphous Crystalline

Temperature3

9

6

7

8

4

5

Glass phase (hard plastic)

Rubber phase (elastomer)

Liquid

Leathery phase

Log (stiffness)Pa



Polymers in the Solid State

1.2

Glass Transition TemperatureCrystalline Structure

POLYMERS IN THE SOLID STATE

Semi-crystalline Amorphous

Glassy Rubbery


• The glass transition, Tg, is temp. below which a polymer OR glass is brittle or glass-like; above that temperature the material is more plastic.

•The Tg to a first approximation is a measure of the strength of the secondary bonds between chains in a polymer; the stronger the secondary bonds; the higher the glass transition temperature.

Polyethylene Tg = 0°C; Polystyrene = 97 °CPMMA (plexiglass) = 105 °C.Since room temp. is < Tg for PMMA, it is brittle at room temp.

For rubber bands: Tg = - 73°C….

Glass Transition Temperature


Crystallization in linear polymers: achieving a very regular arrangement of the mers

Induction of crystallinity● cooling of molten polymer● evaporation of polymer solution● annealing heating of polymer at a specific temperature● drawing stretching at a temperature above Tg

Crystallinity

Increased Density Increases Stiffness (modulus) Reduces permeability Increases chemical resistance Reduces toughness

Effects:


Crystalline morphologies

• Spherulite aggregates of small fibrils in a radial pattern (crystallization

under no stress)

• Drawn fibrillar obtained by drawing the spherulitic fibrils

• Epitaxial one crystallite grown on another; lamella growth on long

fibrils; the so-called shish-kebab morphology (crystallization under

stirring)

Crystalline polymers (vs amorphous polymers)

tougher, stiffer (due to stronger

interactions) higher density, higher solvent

resistance (due to closely packing

morphology) more opaque (due to light

scattering by crystallites)



Characteristics of polymers.Behaviour in exploitation

1.3

Maximum service temperatureCoefficient of frictionFlammabilityTensile strengh at breakCoefficient of linear expansionThermal guidelines






Polyethylene

1.4

Principal Olefin MonomersMechanical Properties of PolyethylenePhysical Properties of Polyethylene

Principal Olefin Monomers

C C

H H

H H

C C

C2H5 H

H H

C C

CH3 H

H H

C C

C5H6 H

H H

CH3

• Ethylene • Propylene

• Butene-1• 4-Methylpentene

Poly n Poly n

Poly n Poly n


Mechanical Properties of Polyethylene• Type 1: (Branched) Low Density of 0.910 - 0.925 g/cc• Type 2: Medium Density of 0.926 - 0.940 g/cc• Type 3: High Density of 0.941 - 0.959 g/cc• Type 4: (Linear) High Density to ultra high density > 0.959

Mechanical PropertiesBranched LowDensity

MediumDensity

HighDensity

Linear High Density

Density 0.91- 0.925 0.926- 0.94 0.941-0.95 0.959-0.965

Crystallinity 30% to 50% 50% to 70% 70% to 80% 80% to 91%

MolecularWeight

10K to 30K 30K to 50K 50K to 250K 250K to 1.5M

TensileStrength, psi

600 - 2,300 1,200 - 3,000 3,100 - 5,500 5,000 – 6,000

TensileModulus, psi

25K – 41K 38K – 75 K 150K – 158K

150K – 158 K

TensileElongation, %

100% - 650% 100%- 965% 10% - 1300% 10% - 1300%

Impact Strengthft-lb/in

No break 1.0 – nobreak

0.4 – 4.0 0.4 – 4.0

Hardness, Shore D44 – D50 D50 – D60 D60 – D70 D66 – D73


Physical Properties of Polyethylene

Physical Properties of polyethylene Branched Low

Density Medium Density High

Density Linear High Density

Optical

Transparent to opaque




Tmelt

98 – 115 C 122 – 124 C 130 – 137 C 130 –137 C

Tg -100 C -100 C -100 C -100 C H20 Absorption

Low < 0.01 Low < 0.01 Low < 0.01 Low < 0.01

Oxidation Resistance

Low, oxides readily

Low, oxides readily

Low, oxides readily Low, oxides readily

UV Resistance

Low, Crazes readily

Low, Crazes readily

Low, Crazes readily Low, Crazes readily

Solvent Resistance

Resistant below 60C

Resistant below 60C

Resistant below 60C Resistant below 60C

Alkaline Resistance

Resistant Resistant Resistant Resistant

Acid Resistance

Oxidizing Acids

Oxidizing Acids Oxidizing Acids Oxidizing Acids

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Polypropylene

1.5

Polypropylene Structure Advantages/Disadvatages of PolypropyleneMechanical Properties of PolypropylenePhysical Properties of Polypropylene

Polypropylene Structure

C C

CH3 H

H H

C C

CH3 H

H H

C C

CH3 H

H H

C C

CH3 H

H H

C C

CH3 H

H H

C C

CH3 H

H H

• Propylene

• Isotactic- CH3 on one side of polymer chain (isolated). Commercial PP is 90% to 95% Isotactic


Advantages/Disadvatages of Polypropylene

• Advantages– Low Cost– Excellent flexural strength– Good impact strength– Processable by all

thermoplastic equipment– Low coefficient of friction– Excellent electrical insulation– Good fatigue resistance– Excellent moisture resistance– Service Temperature to 126oC– Very good chemical resistance

• Disadvantages– High thermal expansion– UV degradation– Poor weathering resistance– Subject to attack by

chlorinated solvents and aromatics

– Difficulty to bond or paint– Oxidizes readily– flammable


Mechanical Properties of Polypropylene

Mechanical Properties of PolypropylenePolypropylene LDPE

(For Comparison)HDPE(For Comparison)

Density 0.90 0.91- 0.925 0.959-0.965

Crystallinity 30% to 50% 30% to 50% 80% to 91%

Molecular Weight 200K to 600K 10K to 30K 250K to 1.5M

Molecular WeightDispersity MWD(Mw/Mn)

Range ofMWD forprocessing

Range of MWDfor processing

Range of MWDfor processing

Tensile Strength,psi

4,500 – 5,500 600 - 2,300 5,000 – 6,000

Tensile Modulus,psi

165K – 225K 25K – 41K 150K – 158 K

TensileElongation, %

100% - 600% 100% - 650% 10% - 1300%

Impact Strengthft-lb/in

0.4 – 1.2 No break 0.4 – 4.0

Hardness, Shore R80 - 102 D44 – D50 D66 – D73


Physical Properties of Polypropylene-Polyethylene

Physical Properties of PolypropylenePolypropylene LDPE HDPE

Optical Transparent toopaque

Transparent toopaque


Tmelt 175 C 98 – 115 C 130 –137 C

Tg -20 C -100 C -100 CH20Absorption

0.01 – 0.03 Low < 0.01 Low < 0.01

OxidationResistance

Low, oxidesreadily

Low, oxidesreadily

Low, oxides readily

UV Resistance Low, Crazesreadily

Low, Crazesreadily

Low, Crazes readily

SolventResistance

Resistantbelow 80C

Resistant below60C

Resistant below 60C

AlkalineResistance

Resistant Resistant Resistant

AcidResistance

OxidizingAcids

Oxidizing Acids Oxidizing Acids


1] Billmeyer, F. W., Textbook of Polymer Science, 3rd ed., Interscience Publishers, 1984 (classic book with excellent treatment of polymer properties) [2] Barth, H. G. and Mays, J. W., Eds., Modern Methods of Polymer Characterization, Wiley, 1991 (covers latest developments at the time of most methods) [3] Brady, Jr., R. F., Ed., Comprehensive Desk Reference of Polymer Characterization and Analysis, American Chemical Society-Oxford, 2003 (survey of characterization and analytical methods) [4] Brandrup, J., Immergut, E. H. ,Grulke, E. A., Abe, A, and Bloch, D. R., Eds., Polymer Handbook, 4th ed., John Wiley and Sons, 2005 (premier handbook of polymer science, listing virtually all polymer characteristics for most polymers) [5] Brydson, J. A., Plastics Materials, Butterworth Heinemann, 2000 (comprehensive treatment of plastics, their synthesis, properties, and applications) [6] Bueche, F., Physical Properties of Polymers, Krieger Publishing, 1979 (emphasis is on polymer physics) [7] Cowie, J.M.G. and Arrighi, V., Polymers: Chemistry and Physics of Modern Materials, 3rd ed., CRC Press 2008 (excellent discussion of physical properties and applications) [8] Heimenz, P.C. and Lodge, T. P., Polymer Chemistry, 2nd ed., CRC Press, 2007 (comprehensive treatment of polymer chemistry - synthesis and physical chemistry) [9] Mark, J.E., Allcock, H. R., and West, R., Inorganic Polymers, Oxford, 2005 (physical chemistry and properties of inorganic polymers) [10] Mark, J. E., Ed., Polymer Data Handbook, Oxford, 1999 (compilation of major classes of polymers and their physical properties)


Reference

[11] Mori, S. and Barth, H. G., Size Exclusion Chromatography, Springer-Verlag, 1999 (comprehensive treatment of SEC, theory and applications) [12] Munk, P. and Aminabhavi, T. M., Introduction to Macromolecular Science, 2nd ed., John Wiley and Sons, 2002 (emphasis on polymer physical chemistry) [13] Nielsen, L. E., Polymer Rheology, Marcel Dekker, 1977 (introductory text on polymer rheology) [14] Richardson, T. L. and Lokensgard, E., Industrial Plastics: Theory and Applications, Delmar, 1996 (practical overview of some important properties and polymer processing) [15] Carraher, Jr., C. E., Seymour/Carraher's Polymer Chemistry, 7th ed., CRC Press, 2007 (popular introduction to polymer chemistry) [16] Seymour, R. B., Engineering Polymer Sourcebook, McGraw Hill, 1990 (good overview of physical properties of engineering polymers) [17] Sperling L. H., Introduction to Physical Polymer Science, 2d d., Wiley-Interscience, 1992 (good treatment of polymer physics and properties) [18] van Krevelen, D. W., Properties of Polymers, 3rd ed., Elsevier, 1990 (in-depth treatment of polymer properties, best resource available) [19] Whistler, R., Industrial Gums, 2nd ed., Academic Press, 1973 (although outdated, gives solid background on the chemistry and properties of cellulosics and polysaccharides) [20] Wu, C. S., Ed., Handbook of Size Exclusion Chromatography, 2nd ed., Marcel Dekker, 2003 (covers all aspects of this important technique). [21] Course: Classes of Polymeric Materials, Joe Greene, CSU, CHICO[22] Course: Engineering Thermoplastics, Joe Greene, CSU, CHICO


Documents

European Plastic Welder Chapter 1: Plastics Co – ASR, Romanian Welding Society P1 – CWS, Czech Welding Society ANB P2 – SLV, Schweisstechnische Lehr- und