Abstract
Starting from an aromatic diamine carrying a pendant cyano group, 2,6-(3-aminophenoxy)benzonitrile, BACN, we have synthesized a thermoplastic linear polyimide, PI-BACN, by polycondensation with 3,3′;4,4′-benzophenone tetracarboxylic dianhydride and two difunctional thermosets: a bismaleimide monomer, BMI-BACN, and a bisacetylenic monomer, BEPA-BACN. Two types of blends with variable proportions of each components have been studied: (i) PI-BACN polyimide and BMI-BACN monomer; (ii) PI-BACN polyimide and BEPA-BACN monomer. These blends were cured at 300°C or 280°C depending on the thermosetting monomer to give semi-interpenetrating polymeric networks (semi-IPNs). Thermomechanical and dynamic mechanical analyses of semi-IPN films indicated phase separation between the linear polyimide and the crosslinked bismaleimide, but showed rather good miscibility between the linear polyimide and the crosslinked bisacetylenic resin. Compared to the basic linear polyimide, the semi-interpenetrating structure led to a reduction of the room temperature adhesive joint strengths but allowed for the conservation of adhesive and mechanical tensile properties in the region of the glass transition temperature of the thermoplastic polymer (Tg240°C).
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