| 摘要 |
<p>The catalyst is one capable of generating free rads. and is sol. in the monomer, which is an aq. suspension. The monomer contains at least 70% vinyl chloride, and a granulating agent and part hydrolysed PVA are added. The blowing agent, azodicarbonamide, may be added as a paste or a dispersion in white spirit stabilised with a laurylymethyl methacrylate - methacrylic acid graft copolymer with lauryl and glycidyl methacrylate - methacrylic acid dispersing agent. Invention gives superior expandible PVC compsns. as the blowing agent does not degas before it is required and upon foaming, the material becomes a semi-gelled porous mass.</p> |
