Investigation of structure property relationships in liquid processible, solvent free, thermally stable bismaleimide-triazine (BT) resins

Three cyanate ester monomer or oligomer species: 2,2-bis(4-cyanatophenyl)propane 1, 1-1-bis(4-cyanatophenyl)ethane (2), and the oligomeric phenolic cyanate (Primaset TM PT30) (3), are blended in various ratios with bis(4-maleimidophenyl)methane, (4), to form binary and ternary mixtures (11 in total) and cured, in the absence of catalysts (3 K/min to 150 °C + 1 hour; 3 K/min to 200 °C + 3 hours), followed by a post cure (3 K/min to 260 °C + 1 hour). The use of liquid monomer, (2), offers the possibility of liquid processing in blends containing minority compositions of bismaleimide. Glycidylmethacrylate is explored as a reactive diluent (2.5-10 wt %) to linked interpenetrating network polymer structures comprising cyanate ester and bismaleimide components with glass transition temperatures of 267-275 oC, depending on composition; the onset of thermo-oxidative degradation ranges from 386-397 oC. When a binary blend of (2) and (3) (with the former in the minority) is co-cured with (4), an excellent balance of properties is achieved with liquid processing, a Tg greater than 400 C and onset of degradation of 425 oC in static air. Kinetic analysis of DSC data using Ozawa and Kissinger methods yield activation energies of between 107112 kJ/mole for a binary blend of (1)90-(4)10, which is in good agreement with literature. Molecular dynamics simulation of the same blend in cured form gave a simulated glass transition temperature of 250 C that is in very close agreement with empirical DMTA data.