Effect Of The Interphase On The Performance Of Cyanate Ester Composites

The interphase is very important part of composite materials. The structure andproperties of the interphase directly affect the performance of composite materials. Thecoupling agents are in favor of enhancing the interracial adhesion between the matrixand fillers. In this paper, based on cyanate ester resin as matrix and glass fiber andnano-SiO₂ as reinforces, firstly the amino silane coupling agent SCA-1 and theterpolymer coupling agent SCA-3 were designed and synthesized and the synthesistechnology of SCA-1 and SCA-1 was optimized. The SCA-1 and SCA-3 werecharacterized by Fourier Transform infrared spectroscopy (FTIR) and NuclearMagnetic Resonance (NMR) and element analysis and Ge1 permeationChromatography (GPC) and the solubility and dielectric properties of the SCA-1 andSCA-3 were investigated. The yield of SCA-1 was enhanced 15% than that of reportedSCA-1. Additionally there are no reports about the coupling agent SCA-3, which wassynthesized by us for the first time and has the latent advantage in the piezoelectricmaterials field due to simple synthesis technology, the narrow distribution of molecularweight, higher dielectric constant and dielectric loss.Secondly, E-glass fibers were treated with the SCA-1 and SCA-3 and Y-aminoproplytriethoxysilane (KH550) and the effect of different treating technology on thesurface properties of E-glass fiber was studied. The results showed that E-glass fiber treated with the coupling agents could increase the hydrophobic of the surface ofE-glass fiber and improve the wettability between the E-glass fiber and cyanate ester.The rank of the wettability and the hydrophobic was treating with SCA-3＞treatingwith SCA-1＞treating with KH-550. The surface free energy of E-glass fiber treatedwith the SCA-1 and SCA-3 and KH-550 and the adhesive energy between the glassfiber and cyanate ester were calculated by using Fowkes-Good geometry equations andYoung-Dupre eqution, respectively.The results showed the surface free energy of glassfiber surfaces was reduced and the rank of the surface free energy was treating withSCA-3＜treating with SCA-1＜treating with KH-550,which was due to differentmolecular structures making the polarity decreased.Thirdly, the wave-transparent composites of E-glass fabric reinforced bisphenol Adicyanate (CE) were prepared. Based on the analysis of cure kinetics of CE, thepreparation technology of E-glass fiber/CE composite was given. The effect of thethree kind coupling agents SCA-1, SCA-3 and KH-550 on the mechanic properties,dielectric properties and water resistance of the E-glass fiber/ CE composites wasstudied. The interfacial binding strength of composites and the uniformity of theinterphase were investigated by dynamic mechanic analysis (DMA). The resultsshowed that the interracial binding strength of composites with SCA-1 was higher andsimultaneously the uniformity of the interphase was better. The interfacial bindingstrength of composites with SCA-3 was lower, which affected the macro-performanceof composites. In compared to using KH-550, the mechanic properties, dielectricproperties and water resistance of composites with SCA-1 were better and themechanic properties and dielectric properties of composites with SCA-3 were lower.But water had little effect on the dielectric properties of composites with SCA-3. Theinterphase fracture morphology was analyzed by using scanning electronic microscopy (SEM). The results were consistent with the results from the analysis of DMA.Fourthly, the surface of nano-SiO₂ was modified byγ-glycidoxyproply-triethoxysilane (KH-560) and macromolecule SCA-3 and nano-SiO₂/CE compositeswere prepared. The effect of the different modified methods on the mechanicproperties, dielectric properties, thermal properties and tribological properties ofnano-SiO₂/CE composites was investigated. Treating with KH-560 and SCA-3 broughtabout distinct modified effect. Especially treating with SCA-3 had a better effect onenhancing the static mechanic properties, dynamic mechanic properties, thermalproperties and anti-wear and friction-reducing of composites. The results from theanalysis of SEM showed that the reason was that the dispersion of nano-SiO₂ treatedwith SCA-3 was better than that of untreated nano-SiO₂ in the matrix. The analysis ofDMA indicated that the interfacial binding strength of composites with SCA-3 wasbetter than that of composites with KH-560 and the explanation from the chemistrystructure was given. These results provide the important theory foundation for thechoice of the different coupling agents used in the different field and the synthesis ofthe new functional coupling agents.