Thermoplastic

A thermoplastic, or thermosoftening plastic, is a plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. A thermoplastic, or thermosoftening plastic, is a plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate by intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid. In this state, thermoplastics may be reshaped and are typically used to produce parts by various polymer processing techniques such as injection molding, compression molding, calendering, and extrusion. Thermoplastics differ from thermosetting polymers which form irreversible chemical bonds during the curing process. Thermosets do not melt when heated, but typically decompose and do not reform upon cooling. Above its glass transition temperature and below its melting point, the physical properties of a thermoplastic change drastically without an associated phase change. Some thermoplastics do not fully crystallize below the glass transition temperature, retaining some or all of their amorphous characteristics. Amorphous and semi-amorphous plastics are used when high optical clarity is necessary, as light is scattered strongly by crystallites larger than its wavelength. Amorphous and semi-amorphous plastics are less resistant to chemical attack and environmental stress cracking because they lack a crystalline structure. Brittleness can be decreased with the addition of plasticizers, which increases the mobility of amorphous chain segments to effectively lower the glass transition temperature. Modification of the polymer through copolymerization or through the addition of non-reactive side chains to monomers before polymerization can also lower it. Before these techniques were employed, plastic automobile parts would often crack when exposed to cold temperatures.These are linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. Acrylic, a polymer called poly(methyl methacrylate) (PMMA), is also known by trade names such as Lucite, Perspex and Plexiglas. It serves as a sturdy substitute for glass for items such as aquariums, motorcycle helmet visors, aircraft windows, viewing ports of submersibles, and lenses of exterior lights of automobiles. It is extensively used to make signs, including lettering and logos. In medicine, it is used in bone cement and to replace eye lenses. Acrylic paint consists of PMMA particles suspended in water. Acrylonitrile butadiene styrene (ABS) is a terpolymer synthesized from styrene and acrylonitrile in the presence of polybutadiene. ABS is a light-weight material that exhibits high impact resistance and mechanical toughness. It poses few risks to human health under normal handling. It is used in many consumer products, such as toys, appliances, and telephones. Nylon belongs to a class of polymers called polyamides. It has served as a substitute mainly for hemp, cotton and silk, in products such as parachutes, cords, sails, flak vests and clothing. Nylon fibers are useful in making fabrics, rope, carpets and musical strings, whereas in bulk form, nylon is used for mechanical parts including machine screws, gears and power tool casings. In addition, it is used in the manufacture of heat-resistant composite materials. Polylactic acid (polylactide) is a compostable thermoplastic aliphatic polyester derived from renewable resources, such as corn starch (in the United States), tapioca roots, chips or starch (mostly in Asia), or sugarcane. It is one of the materials used for 3D printing with fused deposition modeling (FDM) techniques. Polybenzimidazole (PBI, short for Poly-) fiber is a synthetic fiber with a very high melting point. It has exceptional thermal and chemical stability and does not readily ignite. It was first discovered by American polymer chemist Carl Shipp Marvel in the pursuit of new materials with superior stability, retention of stiffness, toughness at elevated temperature. Due to its high stability, Polybenzimidazole is used to fabricate high-performance protective apparel such as firefighter's gear, astronaut space suits, high temperature protective gloves, welders’ apparel and aircraft wall fabrics. In recent years, polybenzimidazole found its application as membrane in fuel cells.