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Curing a thermosetting resin transforms it into a plastic, or elastomer by crosslinking or chain extension through the formation of covalent bonds between individual chains of the polymer. Crosslink density varies depending on the monomer or prepolymer mix, and the mechanism of crosslinking:
Phenolic resins, originally developed in the late 19th century and, regarded as the first truly synthetic polymer types, are often referred to as the “work-horse of thermosetting resins”. They are characterised by high bonding strength, dimensional stability and creep resistance at elevated temperatures, and frequently combined with co ...
Once cured, the part cannot be changed or reformed, except for finishing. Some of the more common thermosets include epoxy, polyurethanes, phenolic and amino resins, bismaleimides (BMI, polyimides), polyamides. [3] [4] [5] Of these, epoxies are the most commonly used in the industry. Epoxy resins have been in use in U.S. industry for over 40 years.
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.
An acrylic resin is a thermoplastic or thermosetting plastic substance typically derived from acrylic acid, methacrylic acid and acrylate monomers such as butyl acrylate and methacrylate monomers such as methyl methacrylate. Thermoplastic acrylics designate a group of acrylic resins typically containing both a high molecular weight and a high ...
Condensites are similar thermoset materials having much the same properties, characteristics, and uses. [77] Crystalate is an early plastic. [78] Faturan is a phenolic resin, also similar to Bakelite, that turns red over time, regardless of its original color. [79] Galalith is an early plastic derived from milk products. [80]
BMC is manufactured by mixing strands (Greater than 1/8” and less than 2" [2] [3]) of chopped glass fibers, styrene, an initiator, and filler in a mixer with an unsaturated thermoset resin (commonly polyester resin, vinyl ester resin or epoxy resin). The mixing is done at room temperature and stored at low temperatures to slow down curing ...
The chemistry of the cure reaction is a trimerization of three CN groups to a triazine ring. When the monomer contains two cyanate groups the resulting structure is a 3D polymer network . Thermoset polymer matrix properties can be fine tuned by the choice of substituents in the bisphenolic compound.