| 摘要 |
Individual strands of expanded polymeric material are made by coating strands of foamable polymeric material with an anti-coalescing agent in an amount sufficient to prevent the strands coalescing during expansion. The expansion is unconfined in at least one direction, and is effected by partially filling a closable vented chamber with the strands so that the ratio of the volume of the chamber occupied by the unexpanded strands to the total volume of the chamber is not more than the ratio of the bulk density of the expanded strands to that of the unexpanded strands, closing the chamber, and heating the strands to cause them to individually expand without subsequent coalescence. The polymeric material is preferably a polymer of a monovinyl aromatic compound, e.g. polystyrene, but may also be a methyl methacrylate or aliphatic olefin polymer, and contains a volatile organic foaming agent, e.g. pentane. Suitable anti-coalescing agents are stearic acid and its salts, e.g. magnesium stearate, silicones, sodium oleate, talc, tricalcium phosphate, potassium lauryl sulphate and combinations of these. The strands are initially about 4 to 5 inches long and 0.125 inch in diameter. When expanded they are suitable for use in packaging. |
