Introduction of Polymer
- 2. • Polymers are widely used advanced materials, which are found almost in every material used in our daily life. The very existence of life is virtually the formation, transformation and decomposition of the polymers. This includes carbohydrates, proteins and nucleic acid in our bodies. • Fibers in clothing; soil where food is grown; protein and starch we eat; elastomers in automobile tyres, paints, plastic wall, floor coverings, foam insulation, dishes, furniture, pipes etc are also polymeric. In-spite of the many varieties like fibers, elastomers and plastic, they all have a similar structure and are governed by same theories.
- 3. DNA Rubber Cellulose Nylon Polyester Wool Teflon Epoxy
- 4. • The word polymer is derived from the Greek words “poly” and “meros” meaning many and parts respectively. Thus polymers or macromolecules are giant molecules made up of multiple repeating units which are joined together by covalent bonds. They have molecular weights at least 100 times greater than those of smaller molecules such as water or methanol. • Examples: PVC(polyvinylChloride), Poly(methylmethacrylate), Nylon -6, Nylon -6,6, Polyurethanes, Polyoxyethylene, Natural rubber, Orlon – PAN, Dacron – PET, etc.
- 5. • Monomer is the basic building unit which repeats itself to form a polymer. • Examples: Ethylene, vinylchloride, styrene, isoprene, chloroprene (2-chlorobuta-1,3-diene),tetrafluoroethylene, acrylonitrile, etc.
- 6. • Degree of polymerization is defined as the number of repeating monomeric units in a polymer. • Degree of polymerization of: (i) = 1000 (ii) = 50000 𝐷𝑒𝑔𝑟𝑒𝑒 𝑜𝑓 𝑝𝑜𝑙𝑦𝑚𝑒𝑟𝑖𝑧𝑎𝑡𝑖𝑜𝑛 = 𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑝𝑜𝑙𝑦𝑚𝑒𝑟𝑖𝑐 𝑛𝑒𝑡𝑤𝑜𝑟𝑘 𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑟𝑒𝑝𝑒𝑎𝑡𝑖𝑛𝑔 𝑢𝑛𝑖𝑡 (If DP = 1 then it is monomer; DP=2 dimer; DP = 3 trimer; DP = 4 tetramer).
- 7. • Polymers with low degree of polymerization are known as oligo polymers and their molecular weight ranges from 500 - 5000. • Many oils are oligomeric, such as liquid paraffin. Plasticizers are oligomeric esters widely used to soften thermoplastics such as PVC. Polybutene is an oligomeric oil used to make putty. • Polymers with high degree of polymerization are known as high polymers and their molecular weight ranges from 10,000 - 2, 00,000.
- 8. Little rhyme or reason is associated with the common names of polymers. • Some names are derived from the origin of the material (Example : Hevea brasilliensis (natural rubber) – meaning rubber plant from Brazil). • Some named after the discoverer (Example : bakelite – discoverer Leo Baekeland). • Some named according to the number of carbons used in their synthesis (Examples : nylon group – Nylon 6, 10; Nylon -6,6; Nylon -6).
- 9. Continue.. • Some names are source based i.e they are based on the common name of the reactant monomer, preceded by the prefix “POLY”. (Examples:Poly(methylmethacrylate);Polystyrenepolypropylene;poly- acrylonitrile;polyvinylchloride; polytetrafluoroethylene). • Some names are structure based (employed for simple polymers and the IUPAC system is used). (Example: Poly(1 chloroethylene)). • Many polymer families are referred to by the name of the particular linkage that connects the polymers. (Examples : Polyamide; Polyurethanes).
- 10. Continue.... • Trade names and abbreviations are also used to describe the materials.(Examples : Orlon –PAN; Dacron – PET). Functionality is the number of reactive sites or number of bonding sites. So a monomer should at least be bi-functional to undergo polymerization. Significance: Depending on the functionality of the monomer used, linear, branched or three dimensional cross linked polymers are obtained. Functionality of molecule = No of reactive sites
- 11. continue... • Bi-functional – Two reactive sites. If the monomers are bifunctional then linear polymers are obtained. Thus they are generally of thermoplastic in nature and usually obtained by addition polymerization. Examples: Ethylene, Acrylonitrile,propene , vinylchloride (reaction at double bond), etc. polymerization polymerization Functionality=2 Functionality=2 n n
- 12. polymerization • Trifunctional – Three reactive sites. If the monomer is trifunctional then cross linked polymers are obtained. They are thermosets and usually obtained by condensation polymerization. Examples : Phenol (substitution reaction due to replaceable hydrogen at three sites), glycerol, etc. Each chain is held together by covalent bonds. So the movement of chain is restricted. This type of polymers is hard and brittle,and possesses high strength, high heat resistance. They are insoluble in solvents. Functionality=2 n
- 13. cross linked structure n • In a mixture of bifunctional and trifunctional, the ratio decides whether the polymer shall be branched or cross linked. • When bifunctional molecule is greater than trifunctional molecules, branched polymer is obtained (n>>b). n b polymerization polymerization Branched polymeric structure
- 14. • When trifunctional molecule is greater than bifunctional molecules cross linked polymer is obtained (n>>b). b n Three dimensional network structure • Tetrafunctional – Four reactive sites. Examples : Acetylene (reaction at triple bond), divinylbenzene, etc.
- 15. polymerization Functionality=4 Monofunctional Trifunctional Functionality Imparted by the presence of easily replaceable hydrogen atoms
- 16. Based on Classification Origin or Source Natural or Synthetic polymers Physical State Amorphous, Crystalline Polymers Backbone Inorganic and Organic Polymers Homopolymers, Heteropolymers and Copolymers Structure Linear Polymers,Branched Polymers,Crossed linked Polymers,Graft Polymers,Blocked Polymers Tacticity Isotactic,Syndiotactic. Atactic polymers Thermal characteristics Thermoplastic, Thermosets Types of Polymerization Addition Polymerization Copolymerisation Condensation Polymerization Applications Fiber,Elastomers, Plastics,Resins
- 17. • Classification Based on Source: Natural, Synthetic Natural polymers: Synthesized in nature (OR) Isolated from natural materials. Examples: Cotton, Silk, Wool, starch, protein, glycogen, rubber, etc. Synthetic polymers: Man made (OR) Synthesized from low molecular weight compounds. Examples: Nylon, Ethylene, etc. • Classification Based on Physical state: Amorphous, Crystalline Amorphous polymers: A polymer with less ordered arrangement of chains and weak inter molecular forces.
- 18. Example: Vinyl polymers etc. Crystalline polymers: A polymer with ordered structure that has been allowed to disentangle and form crystals. The intermolecular forces are high. So greater strength and higher density. Example: Cellulose etc. •Classification Based on Back bone: Inorganic, Organic polymer Inorganic polymers: A polymer with a skeletal structure that does not include carbon atoms in the backbone. Example: Sculpture nitride, Silicon carbide, Glass Silica, etc. Organic polymers: Contains organic frame work. Example: Polyethylene, polystyrene, Polyethylene, etc.
- 19. •Classification Based on Structure: Linear, Branched polymers, Cross linked polymers, Graft copolymers, Block copolymers,Alternate copolymers and Random copolymers HDPE Linear polymers: Contains linear chain. Example: HDPE (High density polyethylene). Branched polymers: Contains branches or extension attached to the polymer chain. Example: LDPE(low density polyethylene).
- 20. LDPE Cross linked polymers: Contains cross links that are covalent bonds, between two or more linear polymeric chains. Examples: Bakelite, any thermosets, etc. Graft copolymers: A branched copolymer in which the backbone and the branches consists of different monomers. Examples: Vinyl chloride – acrylonitrile copolymer, etc. Block copolymers: A copolymer with a long sequence of one monomer followed by long sequence of another monomer. (M1) m X (M2) n. Bakelite
- 21. Graft copolymer Block copolymer • Classification Based on Tacticity:Isotactic , Atactic and Syndiotactic polymers • Tacticity is the arrangement of pendant groups in space. This orientation of groups results in three types of stereo – regular polymers. (Note: Pendant groups are groups attached to the main polymer chain or backbone like methyl groups in polypropylene). Isotactic polymers: Pendant groups are all on the same side of the polymer backbone. Examples: isotactic PP, Isotactic Polystyrene, etc.
- 22. Atactic polymers: Pendant groups are arranged randomly on each side of the polymer backbone. Examples: atactic PP, Atactic Polystyrene, etc. Isotactic polystyrene Atactic polystyrene
- 23. Syndiotactic polymer: Pendant groups are arranged alternatively on each side of the polymer backbone. Example: syndiotactic PP, syndiotactic Polystyrene, etc. Syndiotactic polystyrene
- 24. • Classification Based on Thermal characteristics: Sr.No Thermoplastic Thermosetting 1 Long straight chained carbon compounds Cross linked compounds 2 Formed by addition polymerization Formed by condensation(step growth) polymerization 3 Low strength compared to thermosets More strength compared to thermoplastics 4 Can be processed again and again Cannot be processed again or recycled 5 Eg. Polyethylene Eg. Bakelite,Epoxy • Classification Based on application or end use: Fibers Plastics Elastomers Resins
- 25. Fibers: The polymer drawn into long filament – like materials, whose length is at least 100 times. its diameter is called Fiber. Fibers are linear and drawn in one direction. Examples: Cotton, Silk, Ethylene, Nylon, etc. Plastics: The word plastic originated from Greek, meaning a material which can be molded or formed into any shape of one’s choice. The polymer, shaped into hard and tough utility article by the application of heat and pressure is called plastic. Few Major types of plastics Acrylic plastics: PMMA, PAN Amino plastics: Urea –formaldehyde(UF), MF Cellulosics: Cellulose nitrate, Cellulose acetate Vinyl plastics: PVC, PVC-AC Styrene plastics: PS, ABS
- 26. Elastomers: The polymer with good strength and elongation when vulcanized into rubbery products is called Elastomers. Examples: Vinyl polymers, natural rubber, silicone rubber, etc. Resins Polymers used as adhesives, sealants, etc., in a liquid form is called resins. Examples: polysulphide sealants, epoxy adhesives, silicone resin, etc.
- 27. Focus on the step in front of you, not the whole staircase.