CBSE Chemistry Class 12 project, Study Guides, Projects, Research of Chemistry

Download CBSE Chemistry Class 12 project and more Study Guides, Projects, Research Chemistry in PDF only on Docsity! CHEMISTRY PROJECT SESSION : 2019-2020 ASSIGNED BY _________________________ A STUDY ON POLYMERS SUBMITTED BY : NAME : AAYUSH SINHA CLASS : XII ‘A’ CLASS ROLL NO: 02 BOARD ROLL NO: CERTIFICATE This is to certify that this dissertation titled “A STUDY ON POLYMERS” is submitted by “AAYUSH SINHA” of class XII A to the chemistry department of Oxford Public School, Ranchi. This project is bonafide piece of work carried under my guidance and supervision during academic year 2019-20. …………………………… ...…………………………... INTERNAL EXAMINER EXTERNAL EXAMINER The word ‘polymer’ is coined from two Greek words: poly means many and mer means unit or part. The term polymer is defined as very large molecules having high molecular mass (103-107u). These are also referred to as macromolecules, which are formed by joining of repeating structural units on a large scale. The repeating structural units are derived from some simple and reactive molecules known as monomers and are linked to each other by covalent bonds. This process of formation of polymers from respective monomers is called polymerisation. Polymers can be called as macromolecules. Macromolecules can be considered as an assoc1~t1on of small molecules to give a big molecule. Macromolecules can be man-made, too. The first synthesis were aimed at making substitutes for the natural macromolecules, rubber and silk; but a vast technology has grown up that now produces hundreds of substances that have no natural counterparts. Synthetic macromolecular compounds include: elastomers, which have the particular kind of elasticity characteristic of rubber; fibres, long, thin and threadlike, with the great strength along the fibre that characterizes cotton, wool, and silk; and plastics, which can be extruded as sheets or pipes, painted on surfaces, or moulded to form countless objects. We wear these manmade materials, eat and drink from them, sleep between them, sit and stand on them; turn knobs, pull switches, and grasp handles made of them; with their help we hear sounds and see sights remote from us in time and space; we live in houses and move about in vehicles that are increasingly made of them. CLASSIFICATION OF POLYMERS Classification Based on Source 1. Natural polymers These polymers are found in plants and animals. Examples are proteins, cellulose, starch, some resins and rubber. 2. Semi-synthetic polymers Cellulose derivatives as cellulose acetate (rayon) and cellulose nitrate, etc. are the usual examples of this sub category. 3. Synthetic polymers A variety of synthetic polymers as plastic (polythene), synthetic fibres (nylon 6,6) and synthetic rubbers (Buna - S) are examples of manmade polymers extensively used in daily life as well as in industry. Classification Based on Structure of Polymers Linear polymers : These polymers consist of long and straight chains. The examples are high density polythene, polyvinyl chloride, etc. These are represented as: 2.Branched chain polymers : These polymers contain linear chains having some branches, e.g., low density polythene. These are depicted as follows: 3. Cross linked or Network polymers : These are usually formed from bi-functional and tri-functional monomers and contain strong covalent bonds between various linear polymer chains, e.g. bakelite, melamine, etc. These polymers are depicted as follows: Classification Based on Mode of Polymerisation Addition polymer : (i) Formed by direct addition of repeated monomer's without elimination of any byproduct molecules. (ii)The monomers are generally unsaturated compounds and are generally derivative of ethene (iii) The addition polymers have same empirical formula as their monomers. Condensation polymers: Formed by the condensation of two or more than two monomers with the elimination of simple molecule like H2O/NH3/HCI/ROH- etc. reactive particles can be free radicals, cations, or anions. A typical example is the polymerization of ethylene. Here the chain-carrying particles are free radicals, each of which adds to a monomer molecule to form a new, bigger free radical . (ii) Step reaction polymerization : In step reaction polymerization, there is a series of reactions each of which is essentially independent of the preceding one; a polymer is formed simply because the monomer happens to undergo reaction at more than one functional group. A diol, for example, reacts with a dicarboxylic acid to form an ester; but each moiety of the simple ester still contains a group that can react to generate another ester linkage and hence a larger molecule, which itself can react further, and so on. (iii) Free-radical vinyl polymerization : The polymerization of ethylene and substituted ethylenes under conditions where free radicals are generated – typically in the presence of small amounts of an initiator, such as peroxide. Reaction occurs at the double bonded carbons- the vinyl groups - and is called vinyl polymerization. A wide varity of unsaturated monomers may be used, to yield polymers with different pendant groups(G) attatched to the polymer backbone. For example: (iv) Copolymerization: So far, we have discussed only polymerisation of a single monomeric compound to form a homopolymer, a polymer made up - except, of course, at the two ends of the long molecule - of identical units. Now, if a mixture of two ( or more) monomers is allowed to undergo polymerization, there is obtained a copolymer a polymer that contains two (or more) kinds of monomeric units in the same molecule. It is generally compounded with carbon black and vulcanised with sulphur. It is extremely resistant to wear and tear and finds use in manufacture of tyres and other mechanical rubber goods. (d) Teflon: It is polymer of tetrafluroethylene (F2C=CF2) which on polymerization gives Telfon. It is thermoplastic polymer with a high softening point (600K). It is very tough and difficult to work. It is inert to most chemicals except fluorine and molten alkali metals. It withstands high temperatures. Its electrical properties make it an ideal insulating material for high frequency installation. (e) Nylon-6, 6: It is a polymer resin . It is a condensation polymer formed by reaction between adipic acid and hexamethylene diamine. Both monomer units consist of 6 carbon atoms and therefore named nylon -6, 6. It is thermoplastic polymer When extruded above its melting point (536 K) through spinneret, it gives nylon fiber which is extremely tough and resistant to friction. It possess greater tensile strength, elasticity and lusture than any natural fiber. It is chemically inert and is fabricated into sheet, bristles and textile fibres. (f) Nylon 6 or Perolon-L: A polyamide is prepared by prolonged heating of caprolactam at 530-540 K. The fiber is practically identical to Nylon in properties BIODEGREDABLE POLYMERS A large number of polymers are quite resistant to the environmental degradation processes and are thus responsible for the accumulation of polymeric solid waste materials. These solid wastes cause acute environmental problems and remain undegraded for quite a long time. In view of the general awareness and concern for the problems created by the polymeric solid wastes, certain new biodegradable synthetic polymers have been designed and developed. These polymers contain functional groups similar to the functional groups present in biopolymers. Some biodegradable polymers are given below: 1. Poly β-hydroxybutyrate – co-β-hydroxy valerate (PHBV) It is obtained by the copolymerisation of 3-hydroxybutanoic acid and 3 - hydroxypentanoic acid. PHBV is used in speciality packaging, orthopaedic devices and in controlled release of drugs. PHBV undergoes bacterial degradation in the environment. 12. Glyptal As blinding material in preparation of mixed plastics and paints 13. Nylon 6 In making fibres, plastics, tyre cords and ropes. 14. Nylon 66 In making brushes, synthetic fibres, parachutes, ropes and carpets 15 Bakelite For making gears, protective coatings and electrical fittings. 16. Urea formaldehyde resin For making unbreakable cups and laminated sheets. 17. Melamine formaldehyde resin In making plastic crockery, unbreakable cups and plates CONCLUSION Thus from above study we came to know about polymers and their daily uses, their classification, about their structures, formation, about the mechanism of their formation, monomers and their daily application in real life. BIBILOGRAPHY  www.google.co.in  Wikipedia  NCERT Chemistry Text Book Part 2  Chemistry Teacher