Synthesis Of New Polyphenylene Oxide Microcapsule And Its Application Of Bismaleimide Resin

Being a typical representative of high performance thermosetting resins, bismaleimide (BMI) resins have gained wide attention due to its outstanding integrate properties (such as thermal, dielectric and mechanical properties as well as water absorption). However, as a thermosetting resin, the biggest drawback of BMI resins is their brittleness. Recently, microcapsules can endow materials multi-functions such as toughening and self-healing, and thus have been employed to enhance the performance of polymer. But present microcapsules usually have low thermal-degradation temperature, and can not be applied in developing high performance resins including BMI resins. Hence, synthesizing new microcapsules with better thermal stability, and then discussing its modification of BMI resins is of great interesting.A novel kind of polyphenylene oxide (PPO) microcapsules filled with epoxy resin (PPO-MC) was synthesized by in situ polymerization, of which 2,6-dimethyl-1, 4-phenylene oxide (DMP) is the shell and diglycidyl ether of bisphenol A (DGEBPA) epoxy resin is the core. The effect of different process parameters on surface morphology, size distribution, thermal stability and solvent resistance of microcapsules was investigated. Results illustrate that the optimum synthesizing parameters for microcapsules are:sodium dodecyl sulphate (SDS) is used as the surfactant, the reaction temperature is 30℃, the weight ratio of DMP to DGEBPA is 1:1.2. With the optimum parameters, the synthesized PPO-MC exhibits good thermal stability, its initial degradation temperature is about 258℃.PPO-MC with various diameters and contents was added into BMI/BA resin to develop high performance modified BMI/BA/PPO-MC systems, and the effects of diameter and content of PPO-MC on the processing characteristics, mechanical properties, thermal stability, dielectric properties and water resistance of BMI/BA/PPO-MC resins were investigated in detail. The reactivity of BMI/BA can be catalyzed by the addition of PPO-MC, and the effect becomes pronounced with more PPO-MC content, while the diameter of PPO-MC does not affect the curing of BMI/BA. With increasing the content of PPO-MC, both the impact and flexural strengths increase firstly and then decrease; with the same content of PPO-MC, the smaller the mean diameter of PPO-MC, the better mechanical properties are. The modified BMI/BA resin containing 5wt% PPO-MC with a mean diameter of 80μm has the optimum mechanical properties, specifically, its impact and flexural strengths are about 14.8KJ/m2 and 170MPa, respectively, about 1.15 and 1.20 times of those of original BMI/BA resin. Modified BMI/BA resins have higher glass transition temperature than original BMI/BA resin, while the former has slightly lower thermal-degradation temperature than the later. In addition, the diameter and content of PPO-MC has similar effect on the dielectric constant and loss as that on water absorption, the dielectric constant and loss as well as water absorption initially decrease with the increasing of PPO-MC content, and then increase with further increased PPO-MC content; with the same content of PPO-MC, the smaller the mean diameter of PPOMC, the smaller dielectric constant and loss as well as water absorption are.