Modification of bisphenol-A based bismaleimide resin (BPA-BMI) with an allyl-terminated hyperbranched polyimide (AT-PAEKI)

摘要

As a continuation of previous work involving synthesis of an allyl-functionalized hyperbranched polyimide,AT-PAEKI,we have studied the use of this reactive polymer as a modifier of bisphenol-A based bismaleimide resin (BPA-BMI).This was pursued in anticipation of improvements in processability as well as physical properties including glass transition temperature,elastic modulus,and fracture toughness.Apparent miscibility,indicated by optical clarity with a single T_g,was observed for compositions containing up to 16 wt% AT-PAEKI.Additionally,we observed complete suppression of monomer crystallization and a slight increase in the overall cure exotherm.By rheological characterization,blends containing 4 wt% AT-PAEKI were found to feature a dramatic (65-fold) reduction in the viscosity minimum during heating.Dynamic mechanical analysis (DMA) showed that the addition of 2,4,8 wt%.AT-PAEKI increases the cured modulus by approximately 10% from a base value of 3.4 GPa,while adding 16 wt% AT-PAEKI decreases the modulus slightly to 3.3 GPa.DMA also revealed that the cured glass transition temperature increases monotonically with the addition of AT-PAEKI.Fracture toughness was gauged using the single edge notched beam methodology to yield the critical stress intensity factor,K_(IC).Our results showed a modest toughening effect (from 0.48 to 0.55 MPa m~(1/2)) upon the addition of AT-PAEKI.We conclude that AT-PAEKI may serve as an effective reactive processing aid with slight improvements in T_g,modulus,and fracture toughness.