18 Aug, 2021 By Johny 2 Comments
Function and use of Coupling Agent, Initiator and Low Shrinkage Agent
Coupling agent is a kind of material with two different properties of functional groups. Part of the functional groups in its molecules can react with organic molecules, and the other part of the functional groups can react with the adsorbed water on the surface of inorganic substances to form a firm bond. The function of the coupling agent in the composite material is that it can react with certain groups on the surface of the reinforcing material, and it can also react with the matrix resin to form an interface layer between the reinforcing material and the resin matrix. The interface layer can transfer stress, can strengthen the bonding strength between the reinforced material and the resin, and improve the performance of the composite material. According to the chemical structure and composition of the coupling agent, it is divided into four categories: organic chromium complexes, silanes, titanates and aluminates. Among them, the silane coupling agent is suitable for inorganic fillers such as glass fiber, silica, asbestos, etc., and the surface coating treatment is carried out when the glass fiber is drawn.
Initiator refers to a substance that can activate monomer molecules or low molecules containing double bonds in the linear molecular chain to become free radicals during the polymerization reaction, and carry out a chain reaction. Unsaturated polyester resins can generally undergo a radical copolymerization reaction with the double bonds in the crosslinking agent molecules through an initiator (or light or other initiation methods, etc.) to crosslink linear molecules into body-shaped molecules with a network structure. When the initiator is used to cure the resin, the reaction speed can be effectively controlled, and a suitable accelerator can be added to meet the requirements of the curing process and obtain a product of stable quality.
3.Low shrinkage additives:
Low shrinkage additives can reduce defects caused by shrinkage caused by low molecular weight overflow during curing of unsaturated polyester resin. The type and amount of additives have a great relationship with the shrinkage, performance and surface quality of SMC sheets. Different resin systems are matched with them. The low shrinkage additives are not the same.