Research And Application Of Epoxy Polysiloxane Modified Cyanate Resin

Cyanate ester matrix composites have important applications in wave transmission materials,aerospace materials and printed circuit substrate materials due to their good mechanical properties,high heat resistance and low dielectric loss.With the development of the aerospace industry,the new generation of aerospace structural materials,especially the structural materials of remote sensing aircrafts,are larger in size and lighter in weight,and they demand more strict requirements for dimensional accuracy and stability in the space environment.The printed circuit substrate also demands high dimensional stability at different operating temperature and in humidity environment,in order to avoid the reliability reduction or even failure of line connection caused by size change.Therefore,on the basis of maintaining the mechanical properties and dielectric properties of cyanate ester resin,reducing the moisture absorption of cyanate ester resin and improving the dimensional stability and reliability of composite parts in the application environment have great significance for high-performance aerospace structural composite materials and printed circuit substrate materials.In this thesis,the epoxy-terminated polymethylphenylsiloxane modified cyanate resin and its composites are studied.The introduction of the structure of siloxane bond can reduce the water absorption of cyanate ester resin,but the solubility parameters of the chain structural siloxane and cyanate ester resin are quite different.Therefore,the epoxy groups are introduced at the terminal group to improve the compatibility of siloxane resin and cyanate ester.The synthesized polysiloxane is used to modify bisphenol A cyanate ester to study the thermal,mechanical and hygroscopic properties of the blend resin.The polysiloxane with the best structure and performance is selected to modify the divinylbenzene cyanate(DVBCy),combining with the toughening by thermoplastic resin,a resin matrix and a quartz fiber reinforced prepreg is prepared.The mechanical property,hygroscopic property,dielectric performance and processability of the resin matrix,prepreg and composites are studied.Firstly,the dimethyldiethoxysilane,diphenyldimethoxysilane(DMDPS)and?-glycidyletherpropyltrimethoxysilane(KH560)are used as monomers,and a polysiloxane(EPSi)with the Si-O-Si bond as the main chain and the epoxy group as the terminal group is synthesized by hydrolysis and condensation.The bisphenol A cyanate ester(BADCy)is modified with the epoxy polysiloxane(EPSi)as modifier.The results show that when the epoxy group content is lower than 2.2%,the physical phase separation will occur while the EPSi and BADCy are blending.The Si-OH contained in EPSi will promote the reaction of the whole system,when the addition amount of EPSi1is 25 wt%,the heat resistance and toughness of the blend resin are improved.Moreover,as a hydrophobic chain,the Si-O-Si forms a silicon enrichment surface in the curing process,which reduces the water absorption of the whole blend resin from 2.44%to1.52%,and increases the contact angle between water and the surface of the blend resin from 71.5°to 95.6°.The results also prove the feasibility of using the hydrophobicity of the Si-O-Si bond to reduce the overall water absorption of the blend resin.The resin matrix with the EPSi1/DVBCy as the main body is prepared by modifying the self-made DVBCy with EPSi1.The polyethersulfone(PES)and polyphenolic oxygen(PKHH)are used to toughen the EPSi1/DVBCy.When the content of PKHH is 3.5 wt%,the DSC peak temperature of the toughened blend resin is263°C,the glass transition temperature is 166°C,the tensile strength is 79.26 MPa,the bending strength is 124.84 MPa,the impact strength is 17.91 k J/m~2,and the water absorption decreases from 0.83%to 0.57%.Finally,the composite is prepared with the PKHH/EPSi1/DVBCy blend resin as matrix resin and the QWB quartz fiber cloth as reinforcement material.The mechanical properties,hygroscopic properties and dielectric properties of the composite are studied.The results show that the tensile strength of the composite can reach 642 MPa,its bending strength and interlaminar shear strength is 776 MPa and 72.8 MPa respectively.The water absorption of the composite is only 0.78%,and the contact angle increases to122.0°.