Processible polyimide blends

Abstract

Semi-interpenetrating polymer networks having improved processibility and compatibility are prepared by combining a linear polymer comprised of a thermoplastic polyisoimide and a short chain thermosetting polymer in the form of a cross-linkable oligomer comprised of a thermosetting imide or isoimide oligomer containing unsaturated terminal groups, e.g., an acetylene-, a maleimide-, a nadimide- or a benzocyclobutene-terminated imide or isoimide oligomer. In the resulting blend at least one of the diamine and dianhydride moieties of the structural backbone unit of the polyisoimide and of the cross-linkable oligomer are the same, and preferably both of the components of the blend have the same structural backbone unit. An example of a preferred semi-interpenetrating polymer network is the combination of (1) the polyisoimide produced by reaction of benzophenonetetracarboxylic dianhydride (BTDA) with 1,3-bis (3-amino-phenoxy)benzene (APB) to form the polyamic acid precursor, followed by cyclodehydration thereof, and (2) the acetylene-terminated isoimide oligomer containing BTDA-APB backbone units and marketed as Thermid IP-600 by National Starch Company. Upon curing such semi-interpenetrating network or blend, a polymer having high toughness and high modulus is obtained.