Tesearch On High Performance Resins For Low-cost Liquid Molding Processes

Low-cost techniques for fabricating Advanced Fiber Reinforced Polymeric Composite (APC) have been the hot topic in the field of composites. Resin Transfer Molding (RTM) and Resin Film Infusion (RFI) are typical low-cost techniques, however, for which the matrices should have special processing characteristics besides outstanding mechanical and physical performances. Generally, present high performance resin matrices can only be used to fabricate advanced composites through traditional techniques rather than RTM and RFI. Therefore, developing high performance resins suitable for RTM and RFI to fabricate advanced composites has both great importance in theory and applications.Maleimide-triazine (BD-CE) resin is a kind of high performance resins based on bismaleimides (BMI) and cyanate ester (CE), which has many attractive properties such as outstanding thermal stability and moisture resistance, low dielectric constant and loss, etc., so BD-CE resin has been preferred to be used in many cutting edges industries including aviation, spaceflight, and micro-electronics, etc. But it has been proved to be difficult in balancing the suitable processing and outstanding physical and mechanical performance of BD-CE resin to meet the requirements of RTM and RFI techniques. In addition, its toughness needs to be improved for adcanced composites.In this thesis, a reactive hyperbranched polysiloxane (HBPSi) with epoxy groups was designed and synthesized via the hydrolyzation ofγ-glycidoxypropyltrimetho- xysilane (KH-560), and the effect of synthesizing parameters on the structure and properties of HBPSi were discussed. Results show that the molecular weight (Mw) and viscosity of HBPSi increase with the increase of molar ratio (m) of H2O and KH-560. In addition, methoxy groups can be successfully transformed into siloxane groups by the controlled hydrolyzation of KH-560, and thus obtaining soluble hyperbranched polysiloxane.HBPSi was used to develop two novel high performance modified BD-CE resins (mRTM and mRFI). The effect of the content of HBPSi on the key properties such as processing characteristics and integrated properties of cured resins was discussed in detail. Results reveal that the addition of HBPSi in BD-CE resin can not only improve the processing characteristics of the resin, increase the infiltration to glass fibers, but also significantly improve the thermal, mechanical and dielectric properties of cured resins. For instance, the pot life of mRTM resin is longer than 8h, meeting the requirement of RTM technique (30-45min); mRFI-2 resin has the biggest flexural strength (131MPa), which is about 1.2 times of that of BD-CE resin.Glass woven fabric (GF) reinforced composites (GF/mRTM and GF/mRFI) via RTM or RFI process were prepared and investigated. The contact angle and X-ray Photoelectron Spectroscopy technologies were used to study the nature of the interface. The effect of interface on the thermal and mechanical properties as well as dielectric properties of GF/mRTM and GF/mRFI composites was discussed. Results show that the properties of composites are greatly dependent on the nature of interfacial nature of composites. Compared with BD-CE resin, mRTM and mRFI resins have better interfacial adhesion with GF owing to the formation of chemical bonds. In addition, GF/mRTM and GF/mRFI composites have higher interlaminate shear strengths, better thermal and dielectric properties than GF/BD-CE resin, demonstrating that better interfacial adhesion guarantees a desirable property-transition from the matrix to the resultant composite.mRTM and mRFI resins developed in this thesis are high-performance resins suitable for fabricating APCs with low cost, which also can be served as high-performance electronic packaging materials, adhesives, varnishes and so on, exhibiting great potential in many cutting-edges fields including aerospace and electronic information technologies.