| 摘要 |
Shaped articles comprising a cross-linked stereoregular, polypropylene foam having a uniform cell structure in which at least 50% of the cells are closed are prepared by heating a mixture of stereoregular polypropylene, a blowing agent, and an azido cross-linking agent, to at least the softening temperature of the mixture and sufficient to release the gas from the blowing agent and to effect cross-linking of the polypropylene and forming the foam into a shaped article. Chemical and solvent blowing agents may be used, azobisformamide being the blowing agent exemplified. Azido cross-linking agents exemplified are 1,10-decane-bis(sulfonazide), tetramethylene bis(azidoformate) and a chloroaliphatic poly(sulfonazide). The mixture may be extruded or moulded to form foamed sheets, hollow shapes such as bottles and may be coated on to wire and cables. An elastomer may also be incorporated in the mixture. Suitable elastomers are ethylene propylene copolymers, ethylene-propylene-diene terpolymers and polyisobutylene.
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