The foam pre-expander tells you the foaming method of foam
The foam pre-expansion machine tells you the foaming method of foam. Chemical methods:
can be divided into two categories:
① Using chemical foaming agents, they liberate gas when heated. Commonly used chemical blowing agents, 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 made 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. . Foam artificial leather is mixed with a foaming agent in a PVC paste, scraped or calendered on the fabric, and continuously passed through a tunnel heating furnace. The material is plasticized and melted, the foaming agent is decomposed and foamed, cooled and the surface is finished. Get 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 machine head, the pressure drops to normal pressure, and it expands and foams when it is dissolved in gas. The foaming process and the cooling setting process are properly matched to obtain structural foam products.
②Using 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.