Research On Polymers Grafted Onto Carbon Fiber Surface Induced By Cerium???/HNO₃Redox System And Analysis Of Material Properties

Carbon fiber is an important reinforcement in the resin-based compositematerials. However, the interfacial performance between carbon fiber and resintends to be weak due to poor wettability and adsorption between carbon fiber andthe resin, caused by non-polar and inactive surfaces of carbon fibers. The excellentperformance of composite material couldn't exhibit. In this paper, hydroxyl groupswere introduced to carbon fiber surface and coupled with Ce(IV) salts to initiate thepolymerization of vinyl monomers, resulting polymer grafted onto the surface ofcarbon fiber through the grafting from approach. The polymer could increase theactivity of carbon fiber surface, further, improve the interfacial property and impactresistance of composite materials.The acrylamide, acrylic and methyl methacrylate were grafted polymerizationonto carbon fiber surface and characterized by SEM, DCA, IFSS, and tensilestrength test. The results showed that acrylamide was the best grafting monomer inthe system. When acrylamide is grafted polymerization under45?for5h and theconcentration of Ce(IV) is0.010mol/L, the concentration of HNO3is0.25mol/L, theIFSS of carbon fiber was86.64MPa, reaching the highest value. Compared with thedesized carbon fiber, the IFSS increased by53.29%. Through the XPS and peakfitting analysis of carbon fiber treated by various process, we defined the reactionmechanism of oxidization?chlorination?alcoholysis and graft polymerization ofacrylamide.When the active site of PEG was used as initiator, the amount of PAM graftedonto carbon fiber showed decrease, with the increase of molecular weight of PEG.When the molecular of PEG is200, the amount of PAM grafted onto carbon fibersurface is higest and nitrogen content is10.86%. Block copolymer PEG-b-PAMwas grafted onto the carbon fiber surface and the interfacial property and impactresistance of composite materials were improved. With increasing molecularweight of PEG, the IFSS, ILSS and impact resistance showed decrease after firstincrease. When the PEG molecular weight is400, the mechanical properties of thecomposites was the best, at this time, IFSS is92.61MPa, ILSS is74.79MPa, andthe impact strength is69.35kJ/m2. Combined with fracture surface analysis, thereare two reasons for PEG-b-PAM to improve the interfacial property and impactresistance of composite materials. First, PAM, as the epoxy resin curing agent,could form the chemical bonds with epoxy during the curing process, whichenhances the interfacial chemical bonding. When composite is impacted by loads, the formation energy of crack at the interface is raised because of the excellentinterfacial bonding quality, so the toughness of composite is improved. Secondly,the PEG flexible layer could slow the stress concentration by deformation, whichtransfers the load more effectively. The deformation of PEG expands the crack path,which raises the cracking energy.