Thermosetting resin as a main component, with a variety of optional additives to form a plastic article through crosslinking process.In the post-production process for molding or liquid, insoluble and infusible after curing can not re-melt or soften.Common thermoset plastics have phenolics, epoxy plastics, aminoplasts, unsaturated polyester, alkyd plastics. Thermosetting plastics and thermoplastics synthetic plastic together constitute the two major components system.Thermosetting plastic was divided formaldehyde cross-linking and other cross-linking of two types.
Thermosetting plastics can be softened first heat flow, heated to a certain temperature,the chemical reaction and a crosslinking reaction curing hardens, the change isirreversible, after which, when heated again, can no longer soften the flow.
This characteristic is the use of molding, the use of plastics for the first time flow when heated, filled cavity under pressure, and then cured to determine the shape and size of products.
Thermosetting plastic is characterized at a certain temperature, after a certain time of heat, pressure or hardening agent is added after the chemical reaction and hardening.The chemical structure of the plastic changes after hardening, hard, solvent-insoluble, heat is no longer soften decompose if the temperature is too high.The thermoplastic resin structure of the molecular chains are linear or branched, produce no chemical bonds between the molecular chains, it softens and flows when heated. Cooling hardening process is a physical change.
Formaldehyde cross-linking plastics include phenolics, amino plastics (such as urea - formaldehyde - melamine - formaldehyde, etc.).Other crosslinked plastics include unsaturated polyesters, epoxy resins, diallyl phthalic resins and the like.
Thermosetting plastics commonly used varieties of phenolic resins, urea-formaldehyde resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, polyurethane.