多选题The adhesive can achieve wetting on an adherend when ______. A) The adhesive have a surface tension greater than the adhesive forces between the adherend and adhesive. B) The adhesive must have surface energy lower than does the adherend have. C) The adhesive must have zero or very small contact angle. D) The adhesive must not have cohesive forces.

多选题在低温下，一般固体材料中发生的扩散是______。 a.本征扩散 b.非本征扩散 c.无序扩散

多选题An elastomer has physical cross-links in the network structure. A) NR B) SBS C) SIS D) NBR