Polypropylene Foam Sheet Production Technology
Compared with PS and PE, the development of polypropylene (PP) foam as a major member of the semi-crystalline thermoplastic family has been slow, and commercial production has not yet been achieved in the country. However, PP foam has many unique advantages:
(1) The flexural modulus of PP is about 1.52GPa, which is much higher than that of PE 207MPa. Therefore, the static loading capacity of PP foam is better than that of PE.
(2) The glass transition temperature of PP is lower than room temperature, so the impact performance of PP foam is better than PS foam.
(3) When PS foam is used above 105°C, softening and deformation occur; PE foam is rarely used above 100°C, while PP foam has high heat distortion temperature (165°C), excellent high temperature resistance and can be at high temperature Use in the environment;
(4) PP has very good chemical resistance, comparable to PE;
(5) Due to the presence of pendant methyl groups, PP is prone to beta degradation, and PP foam is easy to recycle, and its environmental friendliness is superior to other foam materials.
It is based on the above advantages that the application of PP foamed materials in many industrial fields, especially in the automotive industry and food packaging industry, is extremely competitive, and can replace the existing PS and PE foams with broad prospects.
However, extrusion foaming of PP is very difficult. The main reason is that the passability of PP is poor, and its processing window for extrusion foaming is very narrow. Experts have estimated that the temperature suitable for foaming with PP is only 4 °C. When the temperature rises to its melting temperature, the melt elasticity of PP decreases sharply, and the lower melt strength cannot guarantee the tensile stress on the cell walls during bubble growth, resulting in the collapse and collapse of the bubbles, resulting in PP. The open rate of the foam is very high and cannot meet the requirements for use. Therefore, in order to prepare a PP foamed material, it is first necessary to improve its expandability from the viewpoint of raw materials.
The polypropylene foam sheet production technology developed by Beijing Technology and Business University adopts domestically-produced polypropylene and high-melt-strength polypropylene produced abroad. Through optimized design, polypropylene foam sheet can be produced on domestically produced equipment, and the cell density can be achieved. 106/cm3, density as low as 0.6g/cm3. Products can be widely used in the automotive industry and food packaging industry.
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