Introduction to Polymers
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This document discusses polymers and their classification and applications. It begins with defining polymers as large molecules formed by linking repeating structural units through covalent bonds, in a process called polymerization. Polymers are classified as natural, semi-synthetic, or synthetic, and as linear, branched, or cross-linked. Thermoplastics are linear or slightly branched polymers that soften on heating and harden on cooling, while thermosettings are heavily cross-linked polymers that set during molding. Common applications described include polyethylene in packaging, polypropylene in packaging and labeling, and polystyrene in containers and disposable items.
Introduction to Polymers
- 1. Anoop S. Nair Assistant Professor Department of Chemistry NSS College Nemmara, Palakkad - 678508 Polymers 1
- 2. Contents • Introduction • Classification • Applications of Various Polymers • Polymer Recycling 2
- 3. • ‘Polymer’ is coined from two Greek words: poly means many and mer means unit • Defined as very large molecules having high molecular mass (103-107u), also referred as MACROMOLECULES • Formed by joining of repeating structural units on a large scale, derived from simple and reactive molecules (Monomers), linked to each other by covalent bonds • The process of formation of polymers from respective monomers is called polymerisation. Introduction What is a POLYMER??? 3
- 4. Classification of Polymers Polymers Natural Semi- synthetic Synthetic Source Eg: Proteins, Cellulose, Starch Eg: Rayon, Cellulose nitrate Eg: Nylon -6,6, Buna -S 4
- 5. Classification of Polymers (Contd…) Polymers Linear Branched Cross- linked Structure Eg: High density polythene, PVC Eg: Low density polythene Eg: Bakelite, Melamine 5
- 6. • These are the linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling • Some common thermoplastics are polythene, polystyrene, polyvinyls, etc. Classification of Polymers (Contd…) Thermosetting Polymers Thermoplastic Polymers • These polymers are cross-linked or heavily branched molecules, which on heating undergo extensive cross- linking in molds and again become infusible • These cannot be reused • Examples are bakelite, urea- formaldelyde resins, etc. 6
- 7. Applications of Polyethene • Polyethylene or polythene (abbreviated PE; polyethene or poly(methylene)) is the most common plastic in use • It is a linear, man-made, addition, homo-polymer • Primarily used for packaging (plastic bags, plastic films, containers including bottles, etc.) • As of 2017, 34% of the total plastics market is PE 7
- 8. Applications of Polypropene • Polypropylene (PP), also known as polypropene, is a thermoplastic polymer made from the monomer propylene • It is the second-most widely produced commodity plastic (after polyethylene) and it is often used in packaging and labeling 8
- 9. 9 Applications of Polystyrene • Polystyrene (PS) is a synthetic aromatic hydrocarbon polymer made from the monomer known as styrene • PS is clear, hard, and rather brittle and is one of the most widely used plastics • Generally used in CD and DVD cases, containers, lids, bottles, trays, tumblers, disposable cutlery
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