| 摘要 |
<p>Chlorinated polyvinyl chloride resin (CPVC) is blended with a block copolymer of styrene and a diene (SD) or of styrene-diene-styrene (SDS), which block copolymer is referred to as a "pro-modifier" because, by itself, it performs a dual function of processing aid and impact modifier in CPVC. For tailoring specific desirable impact properties and physical characteristics into a CPVC resin composition, it may be desirable to use a conventional impact modifier in combination with the block copolymer. When the block copolymer is used, such use being referred to as that of a "co-modifier", the block copolymer and conventional impact modifier provide a CPVC composition with unexpectedly enhanced impact strength. The block copolymer consists essentially of a vinyl aromatic compound and a conjugated diene such as styrene-diene (SD) diblock copolymer, or a styrene-diene-styrene (SDS) polyblock copolymer having a linear or radial block structure, or mixtures of linear and radial block copolymers. When a conventional impact modifier is used, it may be any elastomer additive, preferably a nucleated rubbery graft copolymer, but a minor quantity by weight of a synthetic resinous interpolymer which contains no rubber polymer, may also be used.</p> |
