| 摘要 |
An expansible polyolefin composition comprises (a) a polymer of an olefin containing 2-4 carbon atoms, (b) p p1 - oxy bis (benzenesulphonylhydrazide) and (c) at least one metal salt of a fatty acid having at least 8 carbon atoms, the metal being in the di or tri-valent state. The composition may be expanded by extruding it at a temperature, e.g. between 130 DEG C. and 270 DEG C. at which the sulphonyl hydrazide decomposes but below that at which the hot expanded product collapses, and cooling the expanded product. Preferred polymers are polyethylene and polypropylene. Suitable metal salts are of zinc, calcium, barium, aluminium or magnesium with octoic capric, oleic, palmitic or stearic acid. Antioxidants e.g. p-phenylenediamine, or bis (3 - methyl - 6 - tert butyl phenol) sulphide may be included in the composition. Carbon black, earth metal pigments butyl rubber or inorganic fillers may also be added. The compostion may be formed as an electrical insulator or as a sheet or other form suitable for heat and vapour insulators. The composition may be mixed on roller mills, in Banbury mixers or by dry tumbling the ingredients together. |
