An expandable pelletized material comprising A) a polymer matrix composed of A1) at least 55% by weight of polyester (based on the entirety of components A1) and A2)) with a total enthalpy of fusion of up to 60 J/g, optionally of one or more melting points in the range from 100 to 300° C. and of one or more glass transition temperatures in the range from 0 to 250° C., and A2) from 0 to 45% by weight (based on the entirety of components A1) and A2)) of one or more thermoplastic polymers different from component A1); B) a physical blowing agent component, and C) optionally further additives is suitable for producing moldable foams for use in the automobile industry, airline industry, construction industry, packaging industry, sports and leisure industry, in transport, in engineering, in lightweight construction, and/or in composite construction.