Reaction Mechanism 1.Addition or Chain growth 1.1.Radical polymerization 1.2.Cationic polymerization 1.3.Anionic polymerization 2.Condensation or Step growth Anna University Engineering Chemistry-1(CY6151) Notes Unit-1 Polymer Chemistry Addition Polymerisation Free radical mechanism Addition Polymerization • The key feature of addition polymerizationis that monomers add to one another in such a way that the polymeric product contains all the atoms of the starting monomers. Polymerization in the simplest form can be described as a chemical process that results in the formation of polymers. nCH 2 = CH 2 → − (CH 2CH 2)n − Poly(ethene) is a polymer made from a very large number of ethene molecules combined together. The reaction is performed within an aqueous environment where the monomer species is maintained within a single phase with a suitable surfactant or emulsifier. In the polymerization of ethylene, its pi bond is broken and these two electrons rearrange to create a new propagating center like the one that attacked it. The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections, and to work materials that are brittle, because the material only encounters compressive and shear stresses. Addition polymerization is when the monomer molecules bond to each other without the loss of any other atoms. Polyaddition occurs as a reaction between functional groups on molecules with low degrees of polymerization, such as dimers, trimers and oligomers, to form species of higher molar mass. The monomers are of the same types; they join up to form a polymer. /*]]>*/. Naturally occurring and synthetic polymers can be formed from a variety of monomers. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Polythene. Further, it is important to note that addition polymers can be formed through chain polymerization. The monomers are of the same types; they join up to form a polymer. Many natural materials—such as proteins, cellulose and starch, and complex silicate minerals—are polymers. Polymers are very large molecules. Many polymers are mundane (e.g., plastic bags, food wrap, toys, and tableware), but there are also polymers that conduct electricity, have amazing adhesive properties, or are stronger than steel but much lighter in weight. The best-known brand name of PTFE-based formulas is Teflon (Figure \(\PageIndex{1}\)) Aldehydby Chemours. The polymerization is obtained with a broad molecular weight distribution due to the high viscosity and lack of good heat transfer. poly (ethene) is the polymer The C=C double bond in ethene is involved in the polymerisation reaction. In each step length of chain increases. addition polymerization When a number of monomers undergo self-combination, resulting substance has a molecular mass many times larger than the monomer, the type of polymerization is known as “ Addition polymerization”. Emulsion polymerization is an important process for the production of a wide range of polymeric materials, including paints, adhesives and synthetic rubbers. Gives One! Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. Addition Polymerization ; Condensation Polymerization; 3 Addition Polymerization The entire monomer molecule becomes part of the polymer . Poly(ethene) is a polymer made from a very large number of ethene, The C=C double bond in ethene is involved in the polymerisation reaction. Addition polymers from alkene monomers or substituted alkene monomers are the biggest groups of polymers in this class. Note that all the monomers have carbon-to-carbon double bonds. Addition polymerization definition is - polymerization without formation of a by-product —distinguished from condensation polymerization. The monomers used are mainly the unsaturated compounds. Polymers class 12 Notes Chemistry in PDF are available for free download in myCBSEguide mobile app. Addition polymers are formed by the joining together of many monomers that contain C=C bonds. The polymer formed contains only carbon carbon single bonds. Figure \(\PageIndex{1}\) Advertisement of the Happy Pan, a Teflon-coated pan from the 1960s. It employs a free-radical initiator that donates its unpaired electron to the monomer, making the latter highly reactive and able to form a bond with another monomer at this site. From Wikipedia, the free encyclopedia A polymerization reaction that forms polymers via individual independent addition reactions. Watch the recordings here on Youtube! @media print { Material for the part is fed into a heated barrel, mixed (Using a helical shaped screw), and injected (Forced) into a mould cavity, where it cools and hardens to the configuration of the cavity. Une polymérisation en chaîne est une polymérisation dans laquelle la croissance d'une chaîne polymère résulte exclusivement d'une ou plusieurs réactions entre monomère et site réactif de la chaîne polymère, avec régénération du ou des sites réactifs à la fin de chaque étape de croissance. Depending on the initiator there is a (1) free radical polymerization, (2) cationic polymerization, or (3) anionic polymerization. This highly-crystalline fluorocarbon is exceptionally inert to chemicals and solvents. show an equation for the polymerisation of propene. An example of a cation‐initiated polymerization is the reaction of ethene with sulfuric acid. The hip is much like a ball-and-socket joint, and total hip replacements mimic this with a metal ball that fits in a plastic cup. 1. Water and oils do not wet it, which accounts for its use in cooking ware and other anti-stick applications, including personal care products. The reaction is called a polymerisation reaction: The C=C double bond in ethene is involved in the polymerisation reaction. Addition Polymerisation. Polyvinyl chloride (/ˌpɒlivaɪnəl ˈklɔːraɪd/;[5] colloquial: polyvinyl, vinyl[6]; abbreviated: PVC) is the world's third-most widely produced synthetic plastic polymer, after polyethylene and polypropylene. La polymérisation désigne la réaction chimique ou le procédé par lesquels des petites molécules (par exemple des hydrocarbures de deux à dix atomes de carbone) réagissent entre elles pour former des molécules de masses molaires plus élevées. Compression molding is a forming process in which a plastic material is placed directly into a heated metal mold then is softened by the heat and therefore forced to conform to the shape of the mold, as the mold closes. Alkanes, alkenes, alcohols and carboxylic acids are different homologous series of organic compounds. Examples of addition polymers include polyethylene, polystyrene, PVC etc. /*