THERMOPLASTIC SYNTACTIC FOAMS AND THEIR PREPARATION

摘要

A low-density, porous material is prepared by mixing together microballoons (20) and an oligomeric precursor (22) to a polyetherimide polymer. The oligomeric precursor has an initial viscosity sufficiently low that it can flow and wet the microballoons when first heated to a polymerization processing temperature (30), and thereafter polymerize (30). Fibers (24) may be controllably incorporated into the material during processing to impart specific properties, and air may be controllably incorporated into the material during processing to further decrease its density (32).