Foam plastic is a type of polymer material formed by a large number of gas micropores dispersed in solid plastic, and has the characteristics of light weight, heat insulation, sound absorption, corrosion resistance, and shock absorption.
Compared with non-foam plastics, foam plastics have low density, light weight, high strength, excellent cushioning, shock absorption, sound insulation, sound absorption, low thermal conductivity, good heat insulation performance, excellent electrical insulation, corrosion resistance, and anti-mold performance. Soft foam plastic has excellent elasticity and other properties.
Classification of Foam Plastics
There are currently three types: classified by hardness, which can be divided into soft foam plastics, rigid foam plastics and semi-rigid foam plastics.
At 23°C and 50% relative temperature, soft foam plastics have a modulus of elasticity less than 70MPa. According to the density, they can be divided into three types: low foam plastics, medium foam plastics, and high foam speed. Soft foam plastics have a modulus of elasticity less than 70MPa. Low-foam plastics, with a density of 0.4g/m3 or more, medium-foam plastics, with a density of 0.1/0.4g/m3. Classified by cell structure, cells are divided into two types: closed cell type and open cell type. The pores in the closed cell type are isolated from each other and have floating properties; the pores in the open cell type are connected to each other and have no floating properties. According to the pore size, the ultra-micro pores are 0.1-1.0 μm, the bit pores are 1.0-10 μm, and the general cell pores are above 50μm.
The Foam Processes
No matter what method is used to prepare the foam process, the basic process is foam. The foam process is to turn the plastic into a liquid state, or to introduce gas into the molten plastic to generate micropores (blisters), so that the micropores grow to a certain volume, and the micropore structure is fixed by physical or chemical methods. If it cannot be fixed and the foam is broken, no foam plastics can be formed.
There are three ways to mix gas into plastic polymer materials: mechanical method, physical method, and chemical method. The mechanical means strong stirring. The physical means the normal foam material, the microporous filler, the low boiling point liquid vaporizes, and the blisters are generated by heating. The chemical method is the reaction of solid blowing agent to produce gas.