Flexible bismaleimide resins based on bio-based diamine: Synthesis and properties

The low toughness and high softening temperature of bismaleimide (BMI) resin limit its application in the field of electronic packaging. Herein, a series of flexible BMI resins with maleic anhydride terminated were synthesized via the imide reaction between dianhydrides and bio-based 8,8 '-(4-hexyl-6-octylcyclohexane-1,3-diyl)bis(octane-1-amine) (HOBOA). The degree of polymerization of these BMI resins was controlled to 1, 3, and 5 by adjusting the molar ratio of dianhydrides to HOBOA. These BMI resins show a low softening temperature below 100 degrees C. These BMI resins were cured by the thermal procedure as follows: 145 degrees C/2 h, 185 degrees C/2 h, 225 degrees C/2 h, and 275 degrees C/2 h. The thermal decomposition temperature of cured resins is above 395 degrees C. The tensile testing results demonstrated that cured resins exhibit a high elongation at break of around 60%. The dielectric constant of the cured resins is between 2.72 and 3.09 at room temperature. The water absorption rate of cured resins is less than 0.7% after being soaked in water for 30 days. After the cured resins were soaked separately in acid and alkali, the tensile strength retention rate reaches more than 90%. Additionally, the lap shear strength of cured resins coated on 7075 aluminum alloy exceeds 7.0 MPa. A series of flexible BMI resins based on bio-based diamine were synthesized, which show a low softening temperature below 100 degrees C. The cured resins exhibit a low dielectric constant (around 3.0), a low water absorption of 0.7%, and high elongation at break of about 60%. image