Reducing the shrinkage of cast polyamide mouldings - by adding an inorganic filler to the molten activated lactam monomer casting mixt.

摘要

The shrinkage of cast polyamide mouldings made by anionic activated polymerisation of lactams is reduced by mixing the original melt of monomeric caprolactam, catalyst and activator with a filler. Suitable fillers are e.g. magnesium-, aluminium- or magnesium-aluminium, silicates, perlite, glass fibres, glass microspheres of glass microballoons. Pref. compsns. contain 15-25%, esp. 22 wt.% of a filler comprising glass microballoons with an average particle size of 80 mu and a density of 0.34g/cm3. Addn. of the filler gives mouldings with reduced shrinkage and greater precision. Glass microsphere fillers neither sink nor float and, besides high moulding tolerance, give mouldings of lower density and improve contour precision.