Epoxy Resin Filled Aligned Carbon Nanotube Bundle Hybrid Microcapsule And Its Cyanate Ester Composite

Cyanate ester(CE) resins have been widely applied in electronic information and electronic encapsulated fields owing to their excellent mechanical property, high thermal property and good dielectric property. However, the cured CE resins are brittle due to their high crosslinking density. Therefore, cracks easily occur within the CE matrix during the service period, which can decrease the performance of CE matrix and limit its application field. Additionally, to meet the requirements of outstanding mechanical property and thermal property for high speed development of electronic information materials, it is necessary to enhance the property of CE composites. Studies have shown that embedding microcapsules(MCs) containing healing agent in matrix can effectively heal the cracks within polymer materials to prolong the shelf-life. Moreover, MCs can toughen matrix. Carbon nanotube bundle(CNTB) with highly porous structures has a unique combination of mechanical property, thermal property and electric property. Previous studies showed that the penetration or infiltration of lower molecular polymer or adhesives inside the highly porous multilevel hierarchical structure CNT could improve the specific strength of CNTB, and the prepared lower molecular polymer or adhesives penetrated CNTB was expected to improve the mechanical property, dielectric property and thermal property of polymer matrix. Here we designed a kind of epoxy@ACNTB hybird MCs to apply to CE resins. The prepared MCs can not only heal the cracks within materials but also endow materials with excellent mechanical and thermal properties. The main research study can be described as follows:First, aligned carbon nanotube bundle(ACNTB) and bisphenol A epoxy resin were selected as raw materials, epoxy@ACNTB particles were prepared using solution-soaking method, and dispersed in aqueous solution containing an amine curing agent(FS-2B), the carbon nanotube(CNT)/epoxy resins polymer hybird shell wall could be formed on the surface of epoxy@ACNTB particles via chemical interfacial polymerization, and then epoxy@ACNTB particle MCs with CNT/epoxy resin polymer hybrid shell wall could obtain. The effects of the weight ratio of raw materials on the property and structure of MCs were discussed. The chemical structures of MCs were analyzed using Fourier-transform infrared spectroscopy(FTIR) and X-ray diffraction(XRD). The morphologies of MCs were characterized using scanning electron microscopy(SEM), transmission electron microscopy(TEM) and laser scanning confocal microscopy(LSCM). The thermal properties of MCs were analyzed using thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC). The results show that MCs exhibit high initial decomposition of temperatures Tdi(263~273°C). The content of epoxy resin in MCs is about 62~80% and thickness of the polymer film shell of MCs is from 1 to 2μm. MCs exhibit good thermal and chemical stability below 200°C and excellent solvent resistance in acetone solution.Second, epoxy@ACNTB hybrid MCs were applied to CE resin. The influences of MCs on the mechanical property, the thermal property, flame retardancy, dielectric property and self-healing ability of the CE matrix were discussed in detailed. The results show that the addition of MCs can effectively improve the mechanical property of CE resin, owing to the catalytic effect of MCs on CE resin, the good interfacial interaction between CE and MCs, the improved load transfer ability between CNTs in ACNTB of MCs and the crack pinning or crack blunting effect of MCs. CE system with 5wt% MCs shows the optimal mechanical property, its flexural strength, impact strength, tensile strength and fracture toughness increase by 59%, 45%, 32% and 71%, respectively, as compared with CE. The appropriate addition of MCs can basically maintain the thermal property of the CE matrix. The addition of MCs can improve the dielectric constant of CE resin for the existence of CNT contained in MCs, but has little influence on the dielectric loss of CE resin. The addition of MCs can improve the thermal conductivity of CE resin due to the high thermal conductivity CNT contained in MCs and the good interfacial interaction between MCs and matrix. When MCs contents are 10wt% and 15wt%, the thermal conductivities of CE/MCs are about 16% and 18% higher than that of pure CE resin. Because MCs improve the crosslinking density and the volume of epoxy resin in MCs shrink during the heating process, the addition of MCs can reduce the coefficient of thermal expansion(CTE) value of the matrix. The addition of MCs can promote the formation of compact carbon layer in CE/MCs system during combustion process so as to improve the flame retardancy of the CE matrix. Ruptured MCs under heating condition can release epoxy resin healing agent to crack surface and react with the unreacted-OCN or triazine ring or amine derivatives in the CE matrix, thus rebonding crack surface and recovering the mechanical property of CE matrix. Since epoxy resin healing agent can effectively spread on the crack surface at low temperature, the healing efficiency of fracture CE/MCs system healed at 100°C/1h+200°C/2h is higher than that healed at 200°C/2h. When the healing schedule of 100°C/1h+200°C/2h is applied, the healing efficiency of CE/MCs system with 15wt% can reach 99.8%.