Polymers

• The monomer is the basic unit that makes up a polymer
• Polymers are long chains made up from many repeating units
• Copolymers - molecules which are built up of at least two different kinds of monomer
• Crosslinking - process of forming covalent bonds or relatively short sequences of chemical bonds to join two polymer chains together.
• Elastomer - a natural or synthetic polymer having elastic properties, e.g. rubber.
• Homopolymers - polymers consisting of monomer of identical chemical structure
• Kevlar - a heat-resistant and strong synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, this high-strength material was used first commercially in the early 1970s as a replacement for steel in racing tires.
• Monomer - a molecule that can be bonded to other identical molecules to form a polymer.
• Polymer - a large molecule which is formed by repeated linking of small molecules called "monomers"
• Polymerization - the process by which simple (monomer) molecules join together to form very large (polymer) molecules.
• Resin - a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers.
• Thermoplastic - a material, usually a plastic polymer, which becomes more soft when heated and hard when cooled.
• Thermoset - a polymer that is irreversibly hardened by curing from a soft solid or viscous liquid prepolymer or resin.
• Vulcanization - a process of treating natural rubber with sulphur
• polymers can be very resistant to chemicals.
• polymers can be both thermal and electrical insulators.
• polymers are very light in weight with significant degrees of strength.
• polymers can be processed in various ways.
• Copolymers

  
• homopolymers

  
• Homopolymers can be classified as linear, branched, cross linked and network homopolymers.
• Linear polymers - Considered to be the simplest polymer, linear polymers have linear long polymeric chain of same types of monomer units or simply a chain in which all of the carbon-carbon bonds exist in a single straight line.
• Branched polymers - have short or long branches bonded on parent polymeric or it occurs when groups of units branch off from the long polymer chain.
• copolymers - are also known as heteropolymer as they are composed of two or more different kinds of monomers. It has two major types, namely, polyamides and polyesters.
• Polyamides are the condensation of carboxylic acid and amine monomers
• polyesters are the condensation of carboxyclic acid and alcohol monomers.
• Random Copolymer -the monomers are arranged in any order such as AABAAABBBBAB.
• Block Copolymers - two blocks of homopolymers are joined together. It can be represented as AAAAAAABBBBBBB.
• Alternating Copolymer - the two monomers are arranged in an alternative way and can be represented as ABABABABAB.
• Graft Copolymer -The composition of the main chain is a preformed macromolecule and is compositionally or configurationally different from the side chains or branches w/ repeat units.
• Kevlar is an extended application of Nylon and other polymers have stimulated a strong demand for new “super” fibers with the heat resistance of asbestos, the stiffness of glass, and strength much greater than steel.
• Thermoplastics - polymers become soft on the application of heat and thus can be molded in the desired shape.
• Thermosets - polymers have individual chain bonded covalently during polymerization by application of heat or chemical treatment.
• glass–liquid transition, or glass transition - is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rubbery state as the temperature is increased.
• glass-transition temperature Tg - characterizes the range of temperatures over which this glass transition occurs. It is always lower than the melting temperature, Tm, of the crystalline state of the material, if one exists.
• Elastomers (or rubbers) are polymers with considerable extensions which are reversible, examples are natural and synthetic rubbers.
• fiber forming polymers - are linear macromolecules that are usually suitable for making man-made fibers.
• Polymerization - is a chemical reaction in which two or more molecules combine to form larger molecules that contain repeating structural units.
• Addition Polymerization - involves the addition of monomer units without elimination of any small molecule such as water
• Condensation Polymerization - involves the removal of a small molecule such as water from the reacting species