A Glimpse of Industrial polymers

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Many materials in day to day use are made from natural and synthetic polymers as constituents. Polymer based industries are products of research and development.

Transcript of A Glimpse of Industrial polymers

  • 1.A Glimpse of Industrial Polymers

2. CONTENTS 2 What is polymer and plastic? Two types of polymerization reactions Chain polymerization examples Step growth polymerization examples Comparison of two types Rubber, Vulcanization, Synthetic elastomers Synthetic Fibers Synthetic Films Biodegradable plastic 3. Polymers are large molecules that are formed from relatively small molecular fragments known as monomers that are bonded together repetitively. Wool, cotton, silk, wood and leather are examples of natural polymers that have been known and used since ancient times. This group includes biopolymers such as proteins and carbohydrates that are constituents of all living organisms. Synthetic polymers, which includes the large group knownas plastics, came into prominence in the early twentieth century. 3 4. POLYMERIZATION REACTION 4 Converts monomers into macromolecule. Mayinvolve catalysts. (i) Step growth or Condensation and (ii) Addition or Chain reactions are the two main types of polymerization reactions. Condensation reaction Addition reaction 5. 5 6. 6 7. 7 8. ADDITION POLYMERS 8 9. One of the major breakthroughs in polymer chemistryoccurred in the early 1950s when the German chemist Karl Ziegler discovered a group of catalysts that could efficientlypolymerize ethylene. At about the same time, Giulio Natta (Italian) made the first isotactic (and crystalline) polyethylene. The Zieglar - Natta catalysts revolutionized polymer chemistry by making it possible to control the stereoregularity of these giant molecules. The two shared the 1963 Nobel Prize in Chemistry. 9 10. Step growth polymerization requires that the monomers possess two or more kinds of functional groups that are able to react with each other in such a way that parts of these groups combine to form a small molecule (oftenH2O) which is eliminated from the two pieces. The nowempty bonding positions on the two monomers can then join together .10 11. 11 12. 12 13. 13 14. Thermoset polymer Bakelite 14 15. Phenolic resins 15These are made by condensing one or more types of phenols (hydroxy - substituted benzene rings) with formaldehyde, as illustrated above. This was the first commercialized synthetic molding plastic. The brown material (usually bulked up with wood powder) was valued for its electrical insulating properties (light fixtures, outlets and other wiring devices). 16. Making plastics from polymer A plastic contains a polymerized organic substance of largemolecular weight as an essential ingredient, is solid in its finished state, and in its processing into finished articlescan be shaped by flow. Plasticizers, fillers etc., are also added to alter the properties of the plastic products. Thermosetting plastics are processed by heat curing toproduce an infusible or insoluble product. Thermoplastics are processed by heating to soften themand cooling to harden them. Process may be repeated. 16 17. 17 18. Commercial step growth polymers18 19. 19 20. Raw Materials 20 Monomers: vinyl chloride, ethylene, propylene andsimilar simple hydrocarbons Chemical intermediates : phenol, formaldehyde,hexamethylenetetramine, phthalic anhydride, methyl acrylate and methacrylate Other raw materials: plasticizers, fillers, andreinforcements are also added to alter the properties of the plastic products. 21. RUBBER 21Vulcanization creates disulfide cross-links that prevent the polyisoprene chains from sliding over each other. Thedegree of cross-linking can be controlled to produce a rubber having the desired elasticity and hardness. More recently, other kinds of chemical treatment (such as epoxidation) have been developed to produce rubbers for special purposes. 22. Vulcanization creates disulfide cross-links that prevent the polyisoprene chains from sliding over each other. Thedegree of cross-linking can be controlled to produce a rubber having the desired elasticity and hardness. Morerecently, other kinds of chemical treatment (such as epoxidation) have been developed to produce rubbers for special purposes. 22 23. Synthetic Fibers and their Applications Polyamides They are used in home furnishings,especially carpets. Acrylics and Modacrylics polyacrylonitrile isthe major component of several industrial textile fibers. Spandex It is used in foundation garments,hose, swimwear and other elastic products. 23 24. Other Synthetic Fibers Polyolefins They excel in special cases, such asropes, laundry nets, carpets, blankets and backing for tuffed carpets, but are difficult to dye and their melting point is low. Fluorocarbons It is widely used in pump packingsand shaft bearings. Glass Fibers are used for electrical insulation inmotors and generators, structural reinforcement of plastics, fire-proof wall coverings and tire cords. 24 25. Films are made fromdifferent polymers such as polyesters, polyvinyl chloride, etc.25 26. 3 Common Types of Film Processing Slit-die process produces flat sheets by extrudingthe molten polymer through a slit-die into a quenching water bath or onto a chilled roller. Blow-extrusion Process produces tubular film byusing air pressure to force the molten polymer around a mandrel. Calendering preparation of film is produced byfeeding a plastic mix of polymer, stabilizer, and plasticizers between two heated roll where it is squeezed into a film. 26 27. Biodegradable disposable plastic 27 Interest in biodegradable disposable plastic items has steadily grownbecause of the environmental problems caused by non-degradable synthetic polymers. Disposable packaging materials used to ship and protect purchaseditems as well as disposable containers used for food and drink are of special interest. The idea that one time use items can be disposed of with the peace ofmind, that they will not remain for centuries in a landfill, or as litter, is one of the tenets driving the recent interest in "green" technologies and lifestyles. 28. With packaging materials, the reduction in usage of raw materials, re-use and recycling is of course the best route to sustainable lifestyle. However, for various reasons, in practice, much of thematerial ends up being discarded to a landfill or accidentally shows up as litter.For these instances, it is advantageous to have a plastic material that would biodegrade when exposed to environments where other biodegradable materials are undergoing decay. 28 29. What is Biodegradable? Biodegradation is degradation caused by biological activity, particularly by enzyme action leading to significant changes in the material's chemical structure. In essence, biodegradable plastics should breakdown cleanly, in a defined time period, to simple molecules found in the environment such as carbon dioxide and water. 29 30. Polymer Science and Technology Books 30 F. W. Billmayer, Textbook of Polymer Science 3rdedition, 1984, John Wiley & Sons, Singapore F. Rodriguez, Principles of Polymer systems, 4thedition, 1996, Taylor & Francis. Drydens Outline of Chemical Technology for 21stCentury, 3rd edition, chapter V a) Polymerization Fundamentals, b) Polymerization Technology.