Auxiliary materials
(1) Initiator: Characteristics of initiators are usually signified by active oxygen content, stagnation temperature and half-value period. At present, frequently-used initiators are MEKP, TBPB, BPO, Lm-P, TBPO, BPPD, P-16. They are often used by mixing two or three of them according to different stagnation temperatures in application.
(2) Epoxy curing agent: Frequently-used curing agent are acid anhydrides, tertiary amine, imidazole.
(3) Colourant: Pigment are used as colourant in pultrusion process.
(4) Filler: Filler can decrease the shrink percentage of products, improve dimensional stability, surface finishment and gliding property. It can effectively adjust the viscosity of the resin and make products satisfy different performance requirements. Abrasion resistance, electrical conductivity and thermal conductivity are also be increased. Most fillers can increase products’ impact strength and compression strength except for tensile strength and they have excellent light stability and chemical resistance. Filler can improve pigmentation and reduce the cost. In order to get the best result, it’s better to choose filler with gradient. Surface treatment can increase the quantity of filler used.
(5) Releasing agent: Release agents have extremely low surface free energy and they can soak the die uniformly to demold. Excellent demold result is the essential condition in pultrusion process. External releasing agent is used in the early stage of pultrusion process while silicone oil is frequently used. However, the quantity of releasing agents is big and the surface quality is not satisfactory. So,internal releasing agent is used now. The internal releasing agent is added to the resin and diffuse to the surface of the solidification product at a certain temperature. It creates a piece of separator between die and product to demold.
