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In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening ("curing") a soft solid or viscous liquid prepolymer . [1] Curing is induced by heat or suitable radiation and may be promoted by high pressure or mixing with a catalyst .
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. [3] [4] Thermoplastics differ from thermosetting polymers (or "thermosets"), which form irreversible chemical bonds during the curing process ...
Most polymers, sometimes referred to as resins, may be used, including all thermoplastics, some thermosets, and some elastomers. [13] Since 1995, the total number of available materials for injection moulding has increased at a rate of 750 per year; there were approximately 18,000 materials available when that trend began. [14]
Thermoplastics regain their solid properties upon cooling and can thus be reshaped by polymer processing methods such as extrusion and injection moulding and they can also be recycled. [4] Examples of thermoplastic polymers are polystyrene , polycarbonate , polyethylene , nylon , Acrylonitrile butadiene styrene (ABS), etc.
A thermoset polymer matrix is a synthetic polymer reinforcement where polymers act as binder or matrix to secure in place incorporated particulates, fibres or other reinforcements. They were first developed for structural applications, [ 1 ] such as glass-reinforced plastic radar domes on aircraft and graphite - epoxy payload bay doors on the ...
The phenolic units are mainly linked by methylene and/or ether groups. The molecular weights are in the low thousands, corresponding to about 10–20 phenol units. Obtained polymer is thermoplastic and require a curing agent or hardener to form a thermoset. Hexamethylenetetramine is a hardener added to crosslink novolac. At a temperature ...
Thermoplastics can be deformed reversibly above their glass-transition temperature or their crystalline melting point and be processed by extrusion, injection molding, and welding. Thermosets, on the other hand, are made of molecular chains which are interconnected by covalent bonds to form a stable network.
Urea-formaldehyde (UF), also known as urea-methanal, so named for its common synthesis pathway and overall structure, [1] is a nontransparent thermosetting resin or polymer. It is produced from urea and formaldehyde. These resins are used in adhesives, plywood, particle board, medium-density fibreboard (MDF), and molded objects.