Continuous Resin Transfer Molding Pultrusion Process is developed in late 1970. Glass fiber goes through yarn guide and pre forming system into a continuous resin transfer mold to stabilize the pressure and flow rate, injection of a special resin, glass fiber to fully soak and remove air bubbles, curing mold fully infiltrated and bubble-free glass fiber into the mold in the traction machine under the inside, so as to realize the continuous resin transfer molding (Continuous Resin Transfer Molding Pultrusion Process CRTM) or injection pultrusion. This method is not used in the raw materials of polymer, but two or more than two kinds of liquid monomer or prepolymer, in certain proportion respectively added to the mixing head, evenly mixed under pressure, immediately injected into the closed mold, curing in the mold, forming products. The materials used are liquid, with smaller pressure that can quickly fill the die cavity, and therefore reduces the clamping force and the mold cost is particularly suitable for the production of large-area articles. Reaction injection molding required components by the mixed, immediately quick reaction, and the material can be cured to release a degree. Therefore, to use special materials and formulations, sometimes products also need heat treatment to improve its performance. The key to forming equipment is the design of the structure, mixing head components accurately measure and transport. In addition, the raw material storage tank and mold temperature control are also very important.
Continuous resin transfer molding pultrusion process has the following advantages:
1. Glass fiber fully saturated, FRP products in the production will have little micro bubble content and excellent electrical properties;
2. For the resin system and the atmosphere easy isolation, performance of the product is not easy to be influenced by the environment;
3. Resin for injection maintains the same characteristics;
4. Easy to get transparent products, the product defects (such as inclusion, knotyarn) are easy to find and eliminate.