Preparation And Properties Study On Cross-linked Polystyrene And Its Glass Fiber Reinforced Composites

With the development of microwave communication, electron information as well as national defence military industry, there is great demand for improving properties of Low-k materials. Cross-linked polystyrene (CLPS) is a unique microwave dielectric materials with excellent properties, while there was little report on preparation or structure-properties study on it. In this work, the styrene (St) was used as monomer, divinylbenzene (DVB) as crosslinker and benzoyl peroxide (BPO) as initiator, the CLPS bulk materials were synthesized via free radical crosslinking copolymerization. Moreover, the CLPS prepolymer was used as matrix for fabricating E-glass fiber reinforced cross-linked polystyrene composites via Rein transfer molding technique (RTM). The influence of various of factors on structrue and properties of the CLPS as well as the CLPS/GF composites were discussed in detail.The main content and results as follow:A series of CLPS samples with different micro-structures were obtained by changing the content of the crosslinker. The crosslinking degree was characterized and tested by swelling equilibrium technique and fourier transform infrared spectroscopy (FTIR). The network formation mechanism was discussed. What's more, the influence of the various factors such as variation of crosslinking networks, test frequency as well as thermal treatment on static mechanical properites, dynamic mechanical properites, thermal properites and dielectric properties of CLPS were studied. The results showed that CLPS bulk materials displayed the optimal mechanical properites when the content of the crosslinker was about 2 wt%. The thermal properites of the materials increased with the increasing DVB content. The content of DVB had little effect on dielectric constant of CLPS, while the dielectric loss decreased with the increasing crosslinking density.The surfaces of E-glass fiber were chemical modified with three kinds of vinyl coupling agents. The results indicated that there were differences on the interfacial reaction between CLPS matrix and E-glass fiber surfaces, which was attributed to the different hydrolytic activities of these coupling agents. A better interfacial adhesion was useful for improving mechanical as well as thermal properties of CLPS/GF composites. The mechanical and thermal properties of composites were increased with the increasing crosslinking density. The dielectric constant and dielectric loss increased because of the adding E-glass fiber, but there was littlt effect on the variation trend of the dieletric properties. The fracture surface morphology analysis further conformed that the surface modification was important for improving the interfacial adhesion, the discrepancies of the fracture surfaces verified the rationality of the variation of the properties.