Synthesis And Properties Of A Novel Bismaleimide Resin Containing1,3,4-Oxadiazole Moiety And The Modified Resin Systems Derived Therefrom

Bismaleimides (BMI) possess an excellent bond of properties, such as outstanding thermal stability, moisture resistance, high modulus and favorable processability. However, some shortcomings exist in BMIs, which contain poor solubility in common organic solvents, high melting temperature of BMI monomers and high brittleness of their cured resins due to their high crosslink density. To solve problems mentioned the following steps were taken in this paper:firstly, the molecular design methodology was used to introduce1,3,4-oxadiazole, ether moiety into the molecule structure of BMI which designed to be unsymmetrical,with the aim that improving the processability and enhancing the fracture toughness of the corresponding cured without sacrificing thermostability and mechanical properties. Secondly, a new BMI modified resin system were prepared using the novel BMI as modifier which were expected to obtain excellent integrated properties.In the first instance, a novel chain-extended bismaleimide (P-Miox) containing ether bond and1,3,4-oxadiazole moiety was designed and synthesized, which posses an unsymmetrical structure. The chemical structure of the monomer was confirmed by1HNMR and13CNMR and FT-IR. The P-Miox monomer exhibits good solubility in common organic solvents, enabling an easy solution processing. The monomer was investigated by DSC, it exhibited the similar thermal curing behavior as the normal BMI. The TGA was used to characterize the thermal stability and the result showed the heat resistance was high due to the introduction of the1,3,4-oxadiazole, the ether in the structure improve the flexibility of the molecure without decrease the heat resistance.Secondly, the mixture resins were prepared by the novel BMI and the N, N’-(4,4’-diphenylmethane) bismaleimide in several ratios. The thermal stability and the thermal mechanical property of the cured resin were studied through DSC, TGA, DMA test. The results display the lower melting point (160℃) and larger thermal processing windows than any of the component.Finally,2,2’-diallyl bisphenol A (DABPA) was used to modify the mixture monomer systems, then laminate composites of the modified resins were prepared, and studied their flexural strength, flexural modulus and interlaminar shear strength. The result indicated that the modified resin system with5%mass fraction of P-Miox possess the highest heat resistance, thermal stability, interlaminar shear strength, flexural strength and modulus.