ABSTRACT
Serendipity is required to find a resin in one family of polymers that will have the same shrinkage as one in another family. Tinkering with molding conditions can sometimes mitigate the extent of warpage, but if the end user demands absolute freedom from warpage, and the original resin selection was heavily weighted on that property, it will be fortuitous indeed if a secondary selection is as warp free. The as-molded surface of parts can vary considerably from one polymer to another, and the selection process for the second-choice resin should include what is known on the subject. Or, in a common marketing ploy, surfaces of a mold can be finished to provide the parts with a matte finish, which may obscure major surface differences between natural- and glass-reinforced resins—thus permitting interchangeability between them from the standpoint of both shrinkage and surface.
