Polymers Preparation and Properties
→ Polymers, generally known as plastics, are the backbone of modern era. It would be difficult to imagine the modern era without polymers. Polymers are not only used in household utilities, clothes, but also in vehicles, space-crafts, and medical field. Polymers are now also used in making of artificial organs.
→ Generally, carbon compounds contain 30-40 or less carbon atoms. But in polymers, there are thousands of carbon atoms. This large sized polymers are responsible for special properties of polymers. Giant shape of polymers is due to the special properties of joining together of small moleculer with each other.
→ Polymers are made by both type of molecules j. e. prganic as well as inorganic molecules. In 1920 Staudinger gave the definition of Polymer. According to him, “The substances, whose molecular mass is more than 10,000, are called macromolecules.”
→ In these macromolecules are polymers. The word ‘Polymer’ is derived from two Greek words; ‘Poly’ meaning ‘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 macro molecular on a large scale. The repeating structural units are derived from same simple and reactive molecules known as monomers and are linked to each other by covalent bonds.
→ Process of formation of polymers from respective monomers is called ‘Polymerisation’.
Examples :
Transformation of ethene to polythene
→ Interaction of hexamethylene dia mine and adipic acid leading to the formation of Nylon 6, 6
Formation of poly vinyl chloride by the polyrnerisation of vinyl chloride
Summary of the chapter and glossary
→ Polymer : The moleculs which have more than 10000 molecular mass are called macromolecules and that macromolecules are called polymers.
→ Monomer : Simple and reactive molecules from which the polymer are prepared either by addition or condensation are called monomer.
→ Polymerisation : The process by which monomers are converted into polymers is called polymerisation.
→ Natural Polymers : Polymers found in nature, mostly in plants and animals are called natural polymers. e.g., proteins etc.
→ Semi Synthetic Polymer : Polymers which are obtained by making same modification in natural polymers by artificial means, e.g. nitro-cellulose, cellulose accetate etc.
→ Synthetic Polymer : These are man-made polymers prepored in laboratory. e.g. polyethene, teflon, nylon etc.
→ Linear Polymer : These polymers consist of long and straight chains e.g. high density polyethene, nylon, poly vinyichioride etc.
→ Branched Chain Polymer : These polymers contains linear chain having some branches e.g. low density polyether. glycogen etc.
→ Cross linked or Network Polymers : These polymers are usually formed from bifunctional and trifunctional monomers and contain strong covalent bonds. e.g. Bakelite, malamine etc.
→ Addition Polymers : The addition polymer are formed by the repeated addition of same or different monomers. e.g. Polyethene.
→ Homopolymer : Polymers whose repeating structural units are derived from only one type of monomer units are called homo-polymer. For example Polyethene, PAN, Teflon.
→ Co-polymer : Polymer whoes repeating structural units are derived from t.wo or more types of monomer molecules, are called copolymers e.g. Buna S, Buna N, Nylon, 6, 6 etc.
→ Condensation Polymer : The condensation Polymers are form reaction between different bifunctional or trifunctional monomer units usually with elimination of small molecules like water, alcohol etc. e.g. Nylon 6, 6 and Terylene.
→ Elastomers : There are the Polymer having the weakest intermolecular forces of attraction between the polymer chains. Elastomers thus posses an elastic character e.g. Bu na-S. Neoprene.
→ Artitical Fibre : These are the polymers which have the strongest intermoleculer forces such as hydrogen bond or dipol-dipole interaction. e.g. Nylon 6,6 and Terylene.
→ Thermoplastic Polymer : The polymers intermolecular forces of attraction intermediate between elastomers and fibres. There are linear or slightly branched chain polymers capable of repeately softening on heating. e.g. polyethene, polystryrene etc.
→ Thermosetting Polymer : These polymers are cross linked branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible e.g. Bakelite, Urea formaldehyde resins etc.
Some Important Points
- Average molecular weight can be represented as no average molecular mass and mass average molecular mass.
- Ratio of average molecular weight mass and average number molecular mass is called polydispersity index.
- Polymerisation of diene is done by organometallic compounds. In which Ziegler
- Natta catalyst is main.
- State at which polymer melted are called visco fluid state.
- That temprature at which polymer melts and flow are called flow temprature. It is denoted by
- Natural rubber is obtained by latex of Hevea Brasiliensis Plant, and in reaction with sulphur is called vulcanisation of rubber.
- Proteins, cellulose, starch, nucleic Acids are biopolymers which are divided in the presence of particular enzyme.
- PMMA is poly methyl methaacrylate.
- PAN is polyacronitrile.
- PTFE is Polytetra fluro ethylene and PCTFE is Poly mono chioro fluoro ethylene.
- Mela mine formaldenyde is nonbreakable plastic which are used in making crockery.
- Ziegler Natta is a catalyst which is used in making Polyethene of high density.
- Thermosetting polymer are moulds again but thermo plastics does not moulds again.
- Poly isoprene is natural rubber but neoprene is synthetic Rubber.
- Terylene is Glyptal Polyester but Nylon-6 and Nylon 6, 6 is polyamides.