| 摘要 |
<p>Self extinguishing, acid resistant materials comprise 95-70 pts. wt. PVC and/or PVC copolymers and 5-30 pts. wt. polyacetals and/or their copolymers. The materials are esp. useful for making injection moulded parts which, when encased in moulded rigid PVC casings, have zero or very low adhesion to the casing and low friction. Prods. are useful as pipe liners, injection moulded valves and closure devices, etc. Pref. PVC has a K value of 50-70, esp. 55-60 and the polyacetal is an aldehyde (co)polymer with a mol. wt. of 30,000-60,000 esp. a formaldehyde polymer or a (co)polymer of trioxan with 0.02-4% cyclic acetals or lactones. The compsns. are made by compounding the ingredients in a suitable appts., together with suitable stabilizers, reinforcements, etc., as necessary.</p> |
