Thermosetting plastics (thermosets) are polymer materials that cure, through the addition of energy, to a stronger form. The energy may be in the form of heat (generally above 200 degrees Celsius), through a chemical reaction (two-part epoxy, for example), or irradiation. Polymer is a term used to describe large molecules consisting of repeating structural units, or monomers, connected by covalent chemical bonds. ... Celsius relates to the Celsius or centrigrade temperature scale. ... Epoxy or polyepoxide is a thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in the United... Irradiation is the process by which an item is exposed to radiation. ...

Thermoset materials are usually liquid, powder, or malleable prior to curing, and designed to be molded into their final form, or used as adhesives. Malleability is a physical property of matter, signifying its capability of deformation, especially by hammering or rolling. ... One half of a bronze mould for casting a socketed spear head dated to the period 1400-1000 BC. There are no known parallels for this mould. ... An adhesive is a compound that adheres or bonds two items together. ...

The curing process transforms the resin into a plastic or rubber by a cross-linking process. Energy and/or catalysts are added that cause the molecular chains to react at chemically active sites (unsaturated or epoxy sites, for example), linking into a rigid, 3-D structure. The cross-linking process forms a molecule with a larger molecular weight, resulting in a material with a higher melting point. During the reaction, when the molecular weight has increased to a point so that the melting point is higher than the surrounding ambient temperature, the material forms into a solid material. Subsequent uncontrolled reheating of the material results in reaching the decomposition temperature before the melting point is obtained. A thermoset material cannot be melted and re-shaped after it is cured. Household items made out of plastic. ... Latex being collected from a tapped rubber tree Rubber is an elastic hydrocarbon polymer which occurs as a milky colloidal suspension (known as latex) in the sap of several varieties of plants. ... Vulcanization is an example of cross-linking. ... It has been suggested that this article or section be merged into Catalysis. ... :For other senses of this word, see dimension (disambiguation). ... Vulcanization is an example of cross-linking. ... Physics In physics, melting is the process of heating a solid substance to a point (called melting point) where it turns liquid. ... Physics In physics, melting is the process of heating a solid substance to a point (called melting point) where it turns liquid. ...

Thermoset materials are generally stronger than thermoplastic materials due to this 3-D network of bonds, and are also better suited to high-temperature applications up to the decomposition temperature of the material. They do not lend themselves to recycling like thermoplastics, which can be melted and re-molded. A thermoplastic is a material that is plastic or deformable, melts to a liquid when heated and freezes to a brittle, glassy state when cooled sufficiently. ... Fig. ... The international recycling symbol. ... A thermoplastic is a plastic that softens when heated and hardens again when cooled. ...

Examples

• Vulcanized rubber
• Bakelite, a Phenol Formaldehyde Resin (used in electrical insulators and plastic wear)
• Duroplast
• Urea-formaldehyde foam (used in plywood, particleboard and medium-density fibreboard)
• Melamine (used on worktop surfaces)
• Polyester Resin (used in glass-reinforced plastics/fibreglass (GRP))
• Epoxy Resin (used as an adhesive and in fibre reinforced plastics such as glass reinforced plastic and graphite-reinforced plastic)

Vulcanization, or curing of rubber, is a chemical process in which individual polymer molecules are linked to other polymer molecules by atomic bridges. ... Bakelite is a brand named material based on the thermosetting phenol formaldehyde resin polyoxybenzylmethylenglycolanhydride, developed in 1907–1909 by Dr. Leo Baekeland. ... Duroplast is a composite material used in the body of the Trabant. ... Urea-formaldehyde is a transparent thermosetting resin or plastic, made from urea and formaldehyde heated in the presence of a mild base such as ammonia or pyridine. ... Toy constructed from plywood. ... Melamine Melamine is a strong organic base with chemical formula C3H6N6, with the IUPAC name 1,3,5-triazine-2,4,6-triamine. ... SEM picture of a bend in a high surface area polyester fiber with a seven-lobed cross section Polyester is a category of polymers, or, more specifically condensation polymers, which contain the ester functional group in their main chain. ... The composite Rutan VariEze, a home-build light aircraft Glass-reinforced plastic (GRP), is a composite material or fiber-reinforced plastic made of a plastic reinforced by fine fibers made of glass. ... Fibre reinforced plastic (FRP) is a composite material comprising a polymer matrix reinforced with fibres usually of glass, carbon, or aramid and is commonly used in aerospace, automotive and marine industries. ... Graphite-reinforced plastic or carbon fiber reinforced plastic (CFRP or CRP), is a strong, light and very expensive composite material or fibre reinforced plastic. ...

Methods used to mould thermosets

• Injection moulding (used for objects like milk bottle crates)
• Extrusion moulding (used for making pipes, threads of fabric and insulation for electrical cables)
• Calendering (used for making large sheets of plastic)
• Compression moulding (used to shape most thermosetting plastics)
• Blow moulding (used for bottles)

Injection Molding (United Kingdom Injection moulding) is a manufacturing technique for making parts from thermoplastic material. ... Extrusion Moulding is a manufacturing process used to make pipes, hoses, drinking straws, curtain tracks, rods, and fibres. ... Calendering is a finishing process applied to textiles and paper. ... This page is a candidate for speedy deletion. ... The process of injection blow moulding is used for the production of hollow glass and plastic objects in large quantities. ...

See also

• Thermoplastic
• Vulcanization
• Fusion bonded epoxy coating

A thermoplastic is a material that is plastic or deformable, melts to a liquid when heated and freezes to a brittle, glassy state when cooled sufficiently. ... Vulcanization, or curing of rubber, is a chemical process in which individual polymer molecules are linked to other polymer molecules by atomic bridges. ... Fusion bonded epoxy coating, also known as fusion-bond epoxy powder coating and commonly referred to as FBE coating, is an epoxy powder coating that is widely used to protect steel pipes, rebars and valves from corrosion. ...

External links

• The Plastics Historical Society