1. Using chemical foaming agents, they liberate gas whe […]
1. Using chemical foaming agents, they liberate gas when heated. Commonly used chemical foaming agents for core foam plastics, such as azodicarbonamide, azobisisobutyronitrile, N,N'-dinitrosopentamethylenetetramine, sodium bicarbonate, etc. Many thermoplastics can be made into foam using this method. For example, polyvinyl chloride foam shoes are made by putting a batch of resin, plasticizer, foaming agent and other additives into an injection molding machine. The foaming agent is decomposed in the barrel and the material is foamed in the mold .
2. Foam artificial leather is to mix the foaming agent into the polyvinyl chloride paste, scrape or calender it on the fabric, and continuously pass through the tunnel heating furnace, the material is plasticized and melted, the foaming agent is decomposed and foamed, cooled and surface finished , That is, foam artificial leather. Rigid polyvinyl chloride low-foaming sheets, pipes or profiled materials are formed by extrusion. The foaming agent is decomposed in the barrel. When the material leaves the head, the pressure drops to normal pressure, and it expands and foams when the gas is dissolved. The foaming process and the cooling and setting process are properly matched to obtain structural foam products.
3. Utilize the by-product gas in the polymerization process. A typical example is polyurethane foam. When isocyanate and polyester or polyether undergo polycondensation, part of the isocyanate will react with water, hydroxyl or carboxyl groups to generate carbon dioxide. As long as the gas release rate and the polycondensation reaction rate are adjusted properly, a highly foamed product with very uniform cells can be produced. There are two types of polyurethane foam. The soft open-cell type resembles a sponge and is widely used as cushions for various seats and sofas, as well as sound-absorbing and filtering materials. The rigid closed-cell type is ideal for heat preservation, insulation and shock absorption. And floating materials.