A low-density, porous material is prepared by mixing together microballoons and an oligomeric precursor 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,...http://www.google.es/patents/US5532295?utm_source=gb-gplus-sharePatente US5532295 - Thermoplastic syntactic foams and their preparation
Thermoplastic syntactic foams and their preparation
