| 摘要 |
An expanded ultra-high-molecular-weight polyethylene product having a skin layer, which has good external appearance and to which the functions such as light weight, thermal insulating property, sound absorption, low dielectric constant, impact absorption, flexibility and the like have been imparted without impairing the features inherent to the polymer, such as excellent abrasion resistance, self-lubrication, impact strength, cryogenic properties, chemical resistance and the like, and a process for preparing the expanded product stably are provided. The expanded product of the present invention is an expanded product having a density of from 0.02 to 0.7 g/cm 3 , which is obtained by expanding ultra-high-molecular-weight polyethylene having a viscosity average molecular weight of from 300,000 to 10,000,000. This expanded product can be prepared by adding carbon dioxide to ultra-high-molecular-weight polyethylene in the molten state in an extruder, and expanding the resin by extrusion such that each of the surface temperature and the central part temperature of the resin immediately after discharge from the die may be a predetermined temperature, while at the same time setting the residence time and pressure of the resin at the die section to specific values. |
