Foam prodn from thermoplastics with low crystallinity - by heating blend with blowing agent under inert gas press. in autoclave before cooling and expanding by reheating

摘要

In the prodn of cellular materials from thermoplastics (I) with X-ray crystallinity 15 wt.% at 25 degrees C by blending (I) with a gas-liberating blowing agent (II), heating in a gas-tight closed mould to a temp. above the decompsn temp. of (II) cooling below the softening point of the melt under press. and expanding at atmos or reduced press. above the softening point of (I), the blend is heated in an autoclave under an inert gas press. higher than the press. resulting from the decompsn of (II). The foam has bulk density 20-150 (30-60) g/l and has fine, mainly closed cell structure, with cell size gen. 0.1 mm. It can be used for thermal and acoustic insulation, as core materials for composite boards and as packing material. The technique eliminates the need to use a high press. which is costly and allows the prodn of larger mouldings.