Classification of chemical principle of core foam plast […]
Classification of chemical principle of core foam plastic:
1. By-product gas during the polymerization process, such as polyurethane foam, when isocyanate and polyester or polyether undergo polycondensation reaction, some isocyanate will react with water, hydroxyl or carboxyl to generate carbon dioxide. As long as the gas release speed and the polycondensation reaction speed are adjusted properly, it is possible to produce a highly foamed product with very uniform cells. There are two types of polyurethane foam, soft open-cell shaped like a sponge, widely used as a cushion for various seats and sofas, as well as sound-absorbing and filter materials; hard closed-cell type is ideal for thermal insulation, insulation and shock absorption And floating material.
2. The core foams use chemical blowing agents, which liberate gas when heated. For example, PVC foam shoes are made of resin, plasticizer, foaming agent and other additives into the injection molding machine, the foaming agent is decomposed in the barrel, and the material is foamed in the mold . Foam artificial leather is to mix the foaming agent into the polyvinyl chloride paste, scrape or calender on the fabric, continuously through the tunnel heating furnace, the material is plasticized and melted, the foaming agent decomposes and foams, after cooling and surface finishing, namely Get foam artificial leather.
Rigid PVC low foaming sheet, pipe or profiled material is formed by extrusion. The foaming agent decomposes in the barrel. When the material leaves the head, the pressure drops to normal pressure. When dissolved in gas, it expands and foams. When the foaming process is properly matched with the cooling and shaping process, the structural core foam can be obtained.