EBB 220/3 ENGINEERING POLYMER

1. EBB 220/3ENGINEERING POLYMER DR AZURA A.RASHID Room 2.19 School of Materials And Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, P. Pinang Malaysia

2. COURSE CONTENT • Introduction • Principle of viscoelasticity • Polymer failure (short term & long term) • Polymer Rheology • Polymer types & additives • Polymer processing methods • Elastomer (rubber) • Advanced Polymeric materials • Polymer Composites

3. REFERENCES • R J Young and P A Lovell, Introduction to Polymers, Chapman & Hall, 1992. • R J Crawford, Plastics Engineering, Pergamon Press, 1990. • D H Morton-Jones, Polymer Processing, Chapman & Hall, 1989. • N G McCrum, C P Buckley, C B Bucknall, Principles of Polymer Engineering, Oxford/ University Press, 1988. • R Moore, D E Kline, Properties and Processing of Polymers for Engineers, Prentice-Hall, 1984. • P C Powell, Engineering with Polymers, Chapman and Hall, 1983.

4. MARKING SCHEME Final Exams : 70% Test & Assignment : 30% Contribution: • Dr Azlan 15% • Dr Azura 15% Final Exams : 7 Question  answer 5

5. SOME THOUGHT • What you understand about polymer? • Why it is important?

6. EBB 220/3INTRODUCTION DR AZURA A.RASHID Room 2.19 School of Materials And Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, P. Pinang Malaysia

7. WHAT IS POLYMER?? • Polymers are made up of many many molecules all strung together to form really long chains • This is a polymer. It is a large molecule

8. Poly- means "many" and -mer means "part" or "segment". Mono means "one". So, monomers are those molecules that can join together to make a long polymer chain. • Many many many MONOmers make a POLYmer! usually a single polymer molecule is made out of hundreds of thousands (or even millions!) of monomers! • Sometimes polymers are called "macromolecules" - "macro" means "large"  polymers must be very large molecules • The chemical reactions which monomers joined together to form polymer are called polymerization reactions

9. DIFFERENCES BETWEEN MOLECULE & MONOMER

10. POLYMER SYNTHESIS 2 types of Polymerization Additionpolymerization Condesation polymerization

11. ADDITION POLYMERIZATION Involves a simple addition of monomer molecules to each other without the loss of any atomsfrom the original molecule NOTES: It is possible to produce a saturated long chain polymer from unsaturated monomer

12. CONDENSATION POLYMERIZATION Involves a reaction between bifunctional reactants in which a small molecule is eliminated during each step of the polymer building reaction

13. MOLECULAR WEIGHT OF POLYMERS • The molecular weight of one single macromolecule is equal to the molecular weight of the repeating unit multiplied by number of repeating unit (n) in the molecule. • The molecular weight of Polyethylene (PE)  can be calculated from the formula (C2H4)n =28. If n =1000  the molecular weight of PE will be 2800. • The molecular weight of PE can be vary from below 2000 to above one million according to polymerization reaction conditions. • Some polymers consists of macromolecules with different molecular weight  average molecular weight will be used to describe their molecular weight.

14. Homopolymer Polymer consisting of multiples of the same repeating units as Polyethylene Copolymer Resulted products from two different monomers (e,g A and B) polymerized together Terpolymers Polymers obtained from three different monomers (e.g. A, B and C)

15. TYPES OF COPOLYMER Random copolymer Graft Copolymer -A-B-B-A-A-B-A-B- -A-A-A-A-A-A | B | B | B Alternating copolymer -A-B-A-B-A-B-A-B- Block copolymer -A-A-A-B-B-B-A-A-A-B-B-B

16. CONFIGURATIONS OF MACROMOLECULES • The polymer chain may be linear,Branched or crosslinked. • The properties of polymer depend mainly on: • the length and configuration of the macromolecules, • the extent of interaction among them and • the presence or absence of functional group.

17. CONFIGURATIONS OF MACROMOLECULES Linear Branched Crosslinked

18. POLYMER Polymer can be divided into 4 groups according to their deformation properties in the solid state: Plastomers (thermoplastic) Thermoset (Duromers) ThermoplasticElastomer (TPe) Elastomer (vulcanized rubbers)

19. Plastomer (Thermoplastics) • Polyethylene (PE), Polystyrene (PS) and PVC consist of entangled or branched macromolecules held together by intermolecular forces • In the solid state they deform permanently and do not recover after complete release of the force producing the deformation. • This is because their macromolecules are loose and can slip past each other on the application of pressure.

20. Plastomer are usually supplied in granular or pelleted form & can be repeatedly softened by heating and hardened by cooling within a temperature range characteristic of each plastic. • In the softened state  can be shaped into articles by moulding or extrusion. • The change upon heating is substantially physical  scrap or reject parts can be reprocessed. • Plastomer can be dissolved in suitable solvents & regain their properties when the solvent is evaporated.

21. Elastomer (vulcanized rubbers) • Elastic materials that recover to almost their original shape after complete release of the applied force. • They are insoluable and infusible  can be swell only in solvents such as benzene and methyl ethyl ketone and decompose when heated far beyond the maximum service temperature. • The unique properties because the macromolecules are crosslinked by chemical bonds.

22. The crosslinks prevent the long chain molecules from slipping past each other on the application of force from dissolving in solvents or melting by heating. • The number of crosslinks can be increased until a rigid network results as in the case of hard rubber (ebonit). • Elastomer are produced from crude rubbers  in which a variety of compounding ingredients are incorporated. • The obtained rubber mixtures are usually tacky, thermoplastic and soluble in strong solvents.

23. During vulcanization  the chain molecules of the crude rubber are joined by widely spaced crosslinks. • After having been crosslinks  the soft plastic-like material exhibits a high degree of elastic recovery, losses its tackiness, becomes insoluble in solvents & infusible when heated and more resistant to deterioration caused by aging factors. • Scrap or reject parts cannot be processed unless the crosslinks have been destroyed by chemical or mechanical processes.

24. Thermoplastic Elastomer (TPe) • Block copolymer that possess elastic properties within a certain range of temperature e.g from room temperature -70°C. • The elastic properties are due to physical crosslinks resulting from secondary intermolecules forces such as hydrogen bonding. • These crosslinks disappear when heated above certain temperature and reform immediately on cooling to develop elastic properties.

25. Thermoplastic elastomers fill the gap between non crosslinked plastomers and the chemically crosslinked elastomer. • They can be processed & even reprocessed in the manner of thermoplastic materials without vulcanization. • Some thermoplastic elastomers can be dissolved in common solvents & regain their properties when the solvent is evaporated.

26. TERMOSET (Duromer) Thermosets (duromers) • Phenolic resins, urea & melamine plastics  are rigid materials that are produced from certain reactants. • By heating, they undergo a chemical change in which space network molecules are formed similar to vulcanization of rubber mixtures. • The macromolecules are much tightly crosslinked than those of elastomer. • After been crosslinked  there are infusible and insoluble and the scrap or reject parts cannot be reprocessed.

27. CONFIGURATIONS OF POLYMER TYPES

28. Crystalline & Amorphous structure of polymers • Some polymers are almost completely amorphous under normal condition but may become crystalline when stretched or when conditioned in certain low temperatures ranges. • The term crystalline  to describe a polymer processing both crystalline and amorphous regions. • Those regions are not mechanically separable phases  the same macromolecules may at the same region  semicrystalline

29. Some elastomer particularly crosslinked natural rubbers  have an ability to undergo this kind of crystallization when stretched. • Under the extension force  the chain molecules are oriented in the direction of pull. • Many properties of polymers such as hardness, modulus, tensile strength and solubility  are affected by the degree of crystallinity in the polymer. • Those polymers which do not have the ability to crystallize on stretching exhibit inferior tensile strength.

30. Crystalline region Amorphous region

31. EBB 220/3POLYMER IN ENGINEERING DR AZURA A.RASHID Room 2.19 School of Materials And Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, P. Pinang Malaysia

32. WHY POLYMERS • Within polymers, there are various subgroups which within each subgroup there are many individual polymers each having its own individual portfolio of properties. • Pure polymers are hardly used on their own to make articles or product because polymers have a number of limiting features. • Commonly to use compounds made from polymers and ingredients (additives) selected to confer desirable characteristics. • Plastic referring  plastic polymer + additives • Rubber referring  elastomer + additives

33. Radial tyres for car wheels • Vehicle tyres account for more than half the total use of rubber (combination of SBR and natural rubber) • The rubber in tyre has the following general characteristics: • Corrosion resistance: adequate resistance to water, petrol, oil & salt • Insulation: thick walled tyres tend to get warm especially if under inflated • Fatigue resistance : excellent • Toughness: Adequate resists crack growth provided the rubber is protected from oxidative degradation

34. Flexibility: Modulus ~1 MPa, grips road and seals to wheel rim • Energy absorption: a smooth, quiet ride over rough surfaces (part of the suspension system) • Lubrication: Water is a superb lubricant for rubber; road holding relies on efficient thread design to squeeze water out of the way. • Orientation of plies: Selected to confer desired road holding, suspension and steering characteristics. • Low density: light weight construction • Complicated shape: achieved with repeatable precision

35. Plastics pipes & fitting • About 10% of all pipes and fitting are made from plastics mainly thermoplastics pipe. • Thermoplastics used in pipes have the following general characteristics: • Low density: easy to transport and install. • Corrosion resistance: minimal maintenance, negligible build-up of scale and able to resist aggressive media (by suitable choice of plastic). • Insulation: low thermal conductivity or build in lagging, low electrical conductivity – possible hazard in pumping non-conducting powders • Easy to make: by extrusion of polymer melt through die

36. Colour coded: some plastic are transparent too. • Expansion: thermal expansion must be allowed for in design of the pipe system. • Flammability: the hydrocarbon nature of polymers ensures that all polymers will burn, some more readily than others. • Temperature: the service range is from -5°C. Most plastics can cope with 50°C, relatively few with 100°C under prolonged pressure, one or two survive 200°C. • Stiffness: modulus of the order of few GPa or less • Strength: yield stress usually less than 20 MPa • Toughness: in the range 1-3 MPa, less under cyclic or prolonged load, able to withstand normal use.

37. General properties of polymers • Density: Typically 800-1500 kg/m3 for uniform polymers, foamed or cellular polymers down to 10 kg/m3, heavily filled polymers to about 300 kg/m3 • Insulation: Outstanding insulation, exploited in wire covering and capacitor dielectrics. • Expansion coefficient: At about room temperature, linear expansion coefficient in the approximate range 60-200x10-6 K-1 • Burning: All polymers can be destroyed by flame or excessive heat. The rate of destruction depends on the type of polymer, the surface to volume ratio, the temperature, and the duration of exposure to heat

38. Dimensional stability: A few polymers can absorb some liquids, causing swelling or even dissolution, accompanied by changes in physical properties. • Natural rubber readily absorbs large quantities of hydrocarbons liquids • Nylon absorbs moisture in small quantities, • Chemical resistance: Can be very good but must be depend on the chemical nature of the polymers. • Example : polymer hydrocarbon such as polyethylene are not compatible with hydrocarbon oils. • Some polymers are not oil resistant..

39. Some special features of rubber • Reversible high extensibility: For example up to several hundred percent in gum natural rubber vulcanizates stretched above Tg • Modulus: typically about 106 N/m2 • Energy absorption: There is massive area under the stress-strain curve, even though the modulus is low, which provides a large capacity for strain energy. • Fatigue resistance: For example tyre behaviour. • Toughness: Good resistance to crack growth under cyclic loading if the rubber is protected from oxidative degradation.

40. Some special features of plastics • Modulus: About 109 (N/m2)Pa or less • Range of toughness: Some plastic are tough e,g low density polyethylene, some fragile e.g general purpose polystyrene. • Friction coefficient: Unlubricated, some polymers have coefficients of about 0.3-0.5 • PTFE rubbing on itself about 0.2 • Some soft plastics just adhere.

41. 4. Temperature range: • Amorphous Plastic are not used above Tg. • Partially crystalline used mainly between Tg and fairly well below Tm and some are used a little below Tg. 5. Appearance: • Amorphous Plastic can be very transparent, • Partially crystalline ones can be translucent or opaque • Colour plastics with dyes or pigments