POLYMERIC MATERIALS: introduction to polymer
- 2. INTRODUCTION Describe general concept of polymer. 01 PLASTICCLASSIFICATION Identify plastics classification. 02 CALCULATION Calculate the degree of polymerization, molecular weight and mole fraction of copolymer. 05 STRUCTUREOFPOLYMER State the structure of polymer. 03 POLYMERIZATIONREACTION Discuss the various polymerizationreaction and step. 04 TABLEOFCONTENTS
- 4. • A MONOMER is the single unit or the molecule which is repeated in the polymer chain. • It is the basic unit which makes up the polymer. • The repeat sub unit in the polymer chain is called a mer INTRODUCTION TERMSDEFINATION:MONOMER
- 5. • The word POLYMER comes from the Greek words • “poly” =“many”, and “meros” meaning “parts” or “repeating units” • Polymers are macromolecules formed by repeated linkage of large number of small molecules called monomers • Most polymers are based on carbon and are therefore considered organic chemicals INTRODUCTION TERMSDEFINATION:POLYMER
- 6. • POLYMERIZATION is the chemical process in which large numbers of monomers combine together by covalent bonds to form a polymer with or without the elimination of simple molecules like water, HCl, etc. INTRODUCTION TERMSDEFINATION:POLYMERIZATION
- 7. • PLASTIC word is derived from two Greek words 'plastikos' and 'plastos' which means 'fit for moulding' and 'moulded’. • Plastics in general are referred as polymers because they are made up of polymers. • Plastic is widely used in different forms like bottles, bags, boxes, fibers, films etc. • The term plastics is defined as a mixture (of a polymer with additives) that can be transformed by flowing or moulding in liquid or molten state. INTRODUCTION TERMSDEFINATION:PLASTICS
- 10. PLASTICCLASSIFICATION CLASSESOFPOLYMER CLASSES OF POLYMER THERMOPLASTIC THERMOSET ELASTOMER
- 11. • THERMOPLASTIC: a polymer that can be melted and moulded into a shape that is retained when it is cooled • EXAMPLE : Polyethylene, polyvinylchloride, polypropylene, polystyrene, and nylon • THERMOSET: a polymer that can be moulded when it is first prepared but, once it is cooled, (sometime called “curing”) hardens irreversibly and cannot be re-melted • EXAMPLE : Phenolics, epoxies, and certain polyesters PLASTICCLASSIFICATION CLASSESOFPOLYMER
- 12. • ELASTOMERS: These are rubber – like solids with elastic properties. • In these elastomeric polymers, the polymer chains are held together by the weakest intermolecular forces. • These weak binding forces permit the polymer to be stretched. • A few ‘crosslinks’ are introduced in between the chains, which help the polymer to retract to its original position after the force is released as in vulcanised rubber • EXAMPLE : Natural rubber (vulcanized) Synthetic rubbers PLASTICCLASSIFICATION CLASSESOFPOLYMER
- 14. • AMORPHOUS = The polymer chains are in random arrangement • The CRYSTALLINE region (crystallite) has an orderly arrangement of molecules. The higher the crystallinity, the harder, stiffer, and less flexible polymer • Polymers are semi-crystalline materials. • It means they have both amorphous and crystalline regions. STRUCTUREOFPOLYMER AMORPHOUS&CRYSTALLINE
- 15. • In fact, polymers have regions of crystallinity, called crystallites, embedded in amorphous regions. • Crystallites provide strength and hardness and the amorphous regions provide flexibility to the polymeric material. • Density (crystalline polymer) > density (amorphous polymer) STRUCTUREOFPOLYMER AMORPHOUS&CRYSTALLINE
- 16. • Polymers can be homopolymer or copolymer when the number of monomers are one and two respectively. STRUCTUREOFPOLYMER HOMOPOLYMER&COPOLYMERS • HOMOPOLYMER : if the polymers consist of monomer of identical chemical structure then they are called homopolymers
- 17. • COPOLYMERS : Molecules which are built up of at least TWO different kinds of monomer are known as co-polymers. • Thus, a co-polymer is obtained when TWO OR MORE suitable monomers are polymerised together. • The chains of co-polymer consist of repeating units derived from each monomer. STRUCTUREOFPOLYMER TYPESOFCOPOLYMERS
- 18. • Following are some common types of co-polymers : STRUCTUREOFPOLYMER TYPESOFCOPOLYMERS Alternating co-polymers Block co-polymers Random co-polymers Graft co-polymers
- 19. • The different repeating units alternate in each chain. • If A and B represent two different units then an alternating co-polymer will be represented as: -ABABABAB- STRUCTUREOFPOLYMER ALTERNATINGCO-POLYMERS
- 20. • In such copolymers, block of repeating units of one type alternate with block of another type, e.g. SBS (styrene-butadiene-styrene) -AAAABBBBAAAABBBB- STRUCTUREOFPOLYMER BLOCKCO-POLYMERS
- 21. • In this type of copolymers, the different repeating units are not arranged in a systematic manner but are randomly arranged, -ABAABABBAAABA- • Eg; commercial copolymers of butadiene and acrylonitrile STRUCTUREOFPOLYMER RANDOMCO-POLYMERS
- 22. • In such co-polymers, blocks of one repeating units are attached or grafted to a block of linear polymer, e.g. High impact polystyrene STRUCTUREOFPOLYMER GRAFTCO-POLYMERS
- 23. STRUCTUREOFPOLYMER TACTICITY(STEREOISOMERISM) • The orientation of monomeric units or functional groups in a polymer molecule can take place in an orderly or disorderly manner with respect to the main chain is known as tacticity • The difference in configuration (tacticity) do affect their physical properties.
- 24. • If the groups attached to the carbon are arranged on the same side of the main chain, the polymer is called Isotactic polymer. • The best example is polypropylene. • Isotactic polypropylene has excellent mechanical properties STRUCTUREOFPOLYMER ISOTACTICPOLYMER
- 25. • If the groups attached top the carbon chain are arranged randomly, the polymer is called Atactic polymer. STRUCTUREOFPOLYMER ATACTICPOLYMER Can’t Crystallize
- 26. • If the groups attached to the carbon chain are arranged in an alternating side of the main chain, the polymer is called Syndiotactic polymer. STRUCTUREOFPOLYMER SYNDIOTACTICPOLYMER
- 28. • Polymerization is the process by which simple (monomer) molecules join together to form very large (polymer) molecules. • Hence, the synthesis of large molecular weight polymers by the combination of monomer molecules is termed as polymerization. POLYMERIZATIONREACTION INTRODUCTION
- 29. POLYMERIZATIONREACTION POLYMERIZATIONMETHOD BYOPENING ADOUBLEBOND 01 02 03 BYOPENINGARING BYUSINGMOLECULESHAVINGTWO FUNCTIONALGROUPS • There are three different ways for doing polymerization :
- 30. POLYMERIZATIONREACTION TYPESOFPOLYMERIZATION TYPES OF POLYMERIZATION ADDITION POLYMERIZATION CONDENSATION POLYMERIZATION
- 31. • The addition reaction in which monomers with double bonds are joined together by covalent bonds to form a large molecule (polymer) without the lost of a small molecule . • The product is an exact multiple of the original monomeric molecules. • Monomer for making addition polymer may be alkene or alkene derivatives ( chloroethene) • In formation of addition polymers, the carbon-carbon double bond in each monomer is broken open and replaced by a carbon-carbon single bond. • This enables each of the two carbon atom to form a new single bond with other molecule to form a chain. POLYMERIZATIONREACTION ADDITIONPOLYMERIZATION
- 32. • Addition polymerization reactions proceed by a chain reaction consisting of three important steps : (i) Initiation or the formation of an active centre, (ii) Propagation or the formation of a polymer having the active centre (iii) Termination or removal of the active centre. POLYMERIZATIONREACTION ADDITIONPOLYMERIZATION
- 33. • Model of addition (chain) polymerization: (1) initiation, (2) rapid addition of monomers (3) resulting long chain polymer molecule with n mers at termination of reaction POLYMERIZATIONREACTION ADDITIONPOLYMERIZATION
- 34. • The two different types of active centres have been found to be formed during the addition polymerization, A)Free radical mechanism B) Ionic mechanism. • Free-radical polymerization form only LINEAR molecules. • A FREE RADICAL can be defined as an atom, often part of a larger group, that has an unpaired electron (free electron) that can covalently bond to an unpaired electron (free electron) of another atom or molecule. ADDITIONPOLYMERIZATION INITIATION-ACTIVECENTRE STEP 1
- 35. • It involves the formation of a free-radical from a radical initiator such as benzoyl peroxides, Hydrogen peroxide, H2O2 organic peroxide and other materials that can generate free radicals. • This initiator free radical is produced by many way but one of the important way is decomposition of the compound by sun light, heat, catalyst etc. • Hydrogen peroxide, H2O2 can decompose into two free radicals, as shown by the following equations. Using electron-dot notation for the covalent bonds, ADDITIONPOLYMERIZATION INITIATIONSTEP STEP 1
- 36. • Using straight-line notation for the covalent bonds, • An organic peroxide can decompose in the same way as hydrogen peroxide. • If R-O-O-R represents an organic peroxide, where R is a chemical group, then upon heating, this peroxide can decompose into two free radicals in a manner similar to that of hydrogen peroxide, as ADDITIONPOLYMERIZATION INITIATIONSTEP STEP 1
- 38. • The radical so formed then adds to the monomer to form a new free radical, e.g., it adds to vinyl monomer in the following way ADDITIONPOLYMERIZATION CHAININITIATION STEP 2
- 39. • CHAIN INITIATION (EXAMPLE PVC) ADDITIONPOLYMERIZATION CHAININITIATION STEP 2
- 40. • CHAIN INITIATION (EXAMPLE PE) ADDITIONPOLYMERIZATION CHAININITIATION STEP 2
- 41. • The new free radical now adds to another molecule of monomer to form another new free radical until a large free radical is formed . ADDITIONPOLYMERIZATION PROPAGATIONSTEP STEP 3
- 42. • PROPAGATION STEP (EXAMPLE PVC) ADDITIONPOLYMERIZATION PROPAGATIONSTEP STEP 3
- 43. • PROPAGATION STEP (EXAMPLE PE) • The polymer chains in chain polymerization keep growing spontaneously because the energy of the chemical system is lowered by the chain polymerization process. ADDITIONPOLYMERIZATION PROPAGATIONSTEP STEP 3
- 44. • Termination of chains usually occurs by radical coupling or disproportionation reactions. • By coupling or combination ADDITIONPOLYMERIZATION TERMINATIONSTEP STEP 4
- 45. • Disproportionation: In which a hydrogen atom of one radical centre is transferred to another radical centre. • This results in the formation of two polymer molecules, one saturated and other unsaturated, e.g., ADDITIONPOLYMERIZATION TERMINATIONSTEP STEP 4
- 46. ADDITIONPOLYMERIZATION SUMMARY STEP 1 Free radical generation STEP 2 Chain initiation step STEP 3 Chain propagation step STEP 4 Termination step R represents the active initiator, and . is an unpaired electron. Termination using coupling or combination method Represent with R in the coming step
- 47. • The condensation polymers are formed by repeated condensation reaction between two different bi-functional or tri-functional monomeric units. • In these polymerization reactions, the elimination of small molecules such as water, alcohol, hydrogen chloride, etc. take place. • The examples are terylene (dacron), nylon 6, 6, nylon 6, polyester (PET), etc. CONDENSATIONPOLYMERIZATION
- 48. COMPARISION ADDITIONVSCONDENSATIONPOLYMERIZATION Addition Polymerization Condensation Polymerization Polymer growth mechanism Chain reaction Step by step reactions Initiator needed Yes No Type of monomer Contains carbon-carbon double bond Has reacting bifunctional groups on the ends By product form No Yes Polymer chain characteristics A few, long chains Many not very long chains Branching Possible Unlikely
- 49. CALCULATION 05
- 50. • Since molecules in a given batch of polymerized material vary in length, n for the batch is an average; its statistical distribution is normal. • The mean value of n is called the degree of polymerization (DP) for the batch. • By knowing the value of DP, the molecular weight of the polymer can be calculated. • It is represented by the following relationship, Mn= (DP) M0 Mn is the number molecular weight of the polymer, DP is the degree of polymerization, M0 is the molecular weight of the REPEATING UNIT/monomer. • DP affects properties of the polymer: higher DP increases mechanical strength but also increases viscosity in the fluid state, which makes processing more difficult DEGREEOFPOLYMERIZATION INTRODUCTION
- 51. Calculate the molecular weight of the polythene polymer given DP is 100. (CH2 – CH2)n Polythene here ‘n’ is the DP. Molecular weight of the polythene = DP X Molecular weight of polythene = 100 X 28 = 2800 DEGREEOFPOLYMERIZATION EXAMPLE
- 52. • The NUMBER Average Molecular Weight (Mn) can be determined by, Mn = Σ xi Mi Mn is the number molecular weight of the polymer, xi is the fraction of the total number of chains within each range, Mi is the mean molecular weight of each size range of polymer chains. • The WEIGHT Average Molecular Weight (Mm) can be determined by, fi is the weight fraction of the polymer chains, Mi is again the mean molecular weight of each range. AVERAGEMOLECULARWEIGHT INTRODUCTION
- 53. • Calculate the weight average molecular weight Mm for a thermoplastic that has the following weight fractions fi for the molecular weight ranges listed: AVERAGEMOLECULARWEIGHT EXAMPLE
- 55. A copolymer consists of 70 wt % polystyrene and 30 wt % polyacrylonitrile. Calculate the mole fraction of each component in this material. Moles of polystyrene MWpolystyrene = 9 H atoms × 1 g/mol + 8 C atoms × 12 g/mol = 105 g/mol No. of moles of polystyrene in 100 g of copolymer = 70 g / 105 g/mol = 0.667 mol MWPAN = 3H atoms × 1g/mol + 3C atoms × 12g/mol + 1 Natom × 14g/mol = 53 g/mol No. of moles of polyacrylonitrile in 100 g of copolymer = 30 g / 53 g/mol = 0.566 mol MOLEFRACTIONOFCOPOLYMER EXAMPLE
- 56. • Thus, the mole fractions of the components are calculated as: MOLEFRACTIONOFCOPOLYMER EXAMPLE
- 57. • An ABS copolymer consists of 25 wt% polyacrylonitrile, 30 wt% polybutadiene and 45 wt % polystyrene. Calculate the mole fraction of each component in this material. • MOLEFRACTIONOFCOPOLYMER EXAMPLE2
- 58. CREDITS: This presentation template was created by Slidesgo, including icons by Flaticon, and infographics & images by Freepik THANKS Do you have any questions? Sir.Six.6.NAM.GNAM NUZUL ARDZAN MOKHTAR POLITEKNIK KUCHING SARAWAK Please keep this slide for attribution