Thermosetting property

Thermosetting polymer Thermosetting polymer, also known as Thermosetting plastics (means having the properties of curing after heating and being insoluble and non-melting plastic , for example Epoxy resin . This plastic can only be molded once.

The first heating can soften the flow, heating to a certain temperature, resulting in a chemical reaction a cross-linking curing and hardening, this change is irreversible, and then, when heating again, it can no longer become soft flow. It is with this characteristic that the molding process is carried out, using the first heating plastify Flow, fill the cavity under pressure, and then cure into a product that determines shape and size. This material is called Thermosetting plastics .

Thermosetting plastics are linear or banded before resin curing Branched chain Formed between molecular chains after curing Chemical bond Becomes a three-dimensional network structure, not only can not be melted again, in the solvent can not dissolve.

Mainly used for heat insulation, wear resistance, insulation, high voltage and other plastics used in harsh environments, most of them are thermosetting plastics, the most commonly used should be wok handle and high Low-voltage electrical apparatus .

Commonly used thermosetting plastic varieties are Phenolic resin , Urea-formaldehyde resin , Melamine Resin, Unsaturated polyester resin , epoxy resin, Organosilicone resin , polyurethane Let's wait.

After encountering fire, thermosetting materials will carbonize, do not melt, do not produce soluble droplets, and vary according to the material Carbonization layer At different depths, some materials will produce resistance combustion . Example: Polyurethane will form a carbonization layer on the surface when it meets fire, preventing the flame from going deep. Phenolic resin Carbonized after fire, and continue to flame retardant.

urea-formaldehyde (Urea-formaldehyde) is one of them Thermosetting property Plastic, condensed with urea and formaldehyde polymerization Formed.

Thermosetting plastics have cross-links between polymer chains and chains ( Covalent bond Therefore, the chain and the chain can not slide each other, and will not soften or dissolve when heated. ^[1]