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  1. Polymer By Rahul Kumar Yadav

  2. 1.1 Generals on Polymers Definitions Application of polymers Nomenclature of polymers Classification of polymers Main physical properties of polymers

  3. 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.

  4. Definitions Polymer Large molecule consisting of a number of repeating units with molecular weight typically several thousand or higher Repeating unit The fundamental recurring unit of a polymer Monomer The smaller molecule(s) that are used to prepare a polymer Oligomer A molecule consisting of reaction of several repeat units of a monomer but not large enough to be consider a polymer Single repeat unit: MONOMER Many repeat units: POLYMER Degree of polymerization The number of the repeating units

  5. Application of polymers 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.

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

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

  8. 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 structure The most common method for condensation polymers since the polymer contains different functional groups than the monomer

  9. Nomenclature of polymers PC = Polycarbonat PPE = Polyphenylether SMA = Styrol-Maleinsäureanhydrid ABS = Acrylnitril-Butadien-Styrol PMMA = Polymethylmethacrylat PS = Polystyrol SAN = Styrol-Acrylnitril-Copolymere PVC = Polyvinylchlorid PET = Polyethylenterephthalat (PETP) PBT = Polybutylenterephthalat (PBTP) PA = Polyamid POM = Polyoxymethylen RF-PP = Resorcin-Formaldehyd-Polypropylen PE-UHMW = Polyethylen-ultra high molecular weight PP = Polypropylen PE-HD = Polyethylen hoher Dichte (High Density) PE-LD = Polyethylen niedriger Dichte (Low Density)

  10. Classification of polymers • Main classifications of the polymers: • by origin • by Monomer composition • by chain structure • by thermal behaviour • by kynetics or mechanism • by application A. Classification by Origin • Synthetic organic polymers • Biopolymers (proteins, polypeptides, polynucleotide, polysaccharides, natural rubber) • Semi-synthetic polymers (chemically modified synthetic polymers) • Inorganic polymers (siloxanes, silanes, phosphazenes)

  11. B. Classification by Monomer Composition • Homopolymers • Copolymers • Block • Graft • Alternating • Statistical Homopolymers Consist of only one type of constitutional repeating unit (A) AAAAAAAAAAAAAAA Homopolymer

  12. Copolymers Consist of two or more constitutional repeating units (A-B ) Statistical 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 Alternating Block Graft

  13. 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 Cross-linked Network Branched Direction of increasing strength

  14. 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

  15. 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

  16. e. Classification Based on Kinetics or Mechanism • Step-growth • Chain-growth f. Classification by Application • Plastics • Fibers • Elastomers • Coatings • Adhesives

  17. Main physical properties of polymers 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 brittleness 7 – Crystalline melting temperature (Tm): temperature at which crystalline polymers melt 8 - Glass transition temperature (Tg ) : temperature at which an amorphous polymer converts to a liquid or amorphous domains of a semi crystalline polymer melt 9 – Thermoplastics (plastics( :polymers that undergo thermally reversible Interconversion between the solid state and the liquid state 10- Thermosets : polymers that continue reacted at elevated temperatures generating increasing number of crosslinks such polymers do not exhibit melting or glass transition 11- Liquid – crystalline polymers : polymers with a fluid phase that retains some order 12- Elastomers : rubbery , stretchy polymers the effect is caused by light crosslinkingthat pulls the chains back to their original state

  18. Glass phase (hard plastic) 9 Log (stiffness)Pa 8 Leathery phase 7 6 Rubber phase (elastomer) 5 4 Liquid 3 Temperature Amorphous Crystalline

  19. 1.2 Polymers in the Solid State Glass Transition Temperature Crystalline Structure

  20. POLYMERS IN THE SOLID STATE Amorphous Semi-crystalline Glassy Rubbery

  21. Glass Transition Temperature • 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 °C • PMMA (plexiglass) = 105 °C. • Since room temp. is < Tg for PMMA, it is brittle at room temp. • For rubber bands: Tg = - 73°C….

  22. Crystallinity • 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 Effects: • Increased Density • Increases Stiffness (modulus) • Reduces permeability • Increases chemical resistance • Reduces toughness

  23. 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) • 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)

  24. 1.3 Characteristics of polymers. Behaviour in exploitation Maximum service temperature Coefficient of friction Flammability Tensile strengh at break Coefficient of linear expansion Thermal guidelines

  25. 1.4 Polyethylene Principal Olefin Monomers Mechanical Properties of Polyethylene Physical Properties of Polyethylene

  26. H H C C H H H H H H H H C C C C C C C2H5 CH3 C5H6 H H H CH3 Principal Olefin Monomers • Ethylene • Propylene Poly n Poly n • 4-Methylpentene • Butene-1 Poly n Poly n

  27. 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

  28. Physical Properties of Polyethylene

  29. 1.5 Polypropylene Polypropylene Structure Advantages/Disadvatages of Polypropylene Mechanical Properties of Polypropylene Physical Properties of Polypropylene

  30. H H H H H H H H H H H H C C C C C C C C C C C C CH3 CH3 CH3 CH3 CH3 CH3 H H H H H H Polypropylene Structure • Propylene • Isotactic- CH3 on one side of polymer chain (isolated). Commercial PP is 90% to 95% Isotactic

  31. Advantages/Disadvatages of Polypropylene • 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 • 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

  32. Mechanical Properties of Polypropylene

  33. Physical Properties of Polypropylene-Polyethylene

  34. Reference 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)

  35. [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

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