Study On Kevlar Fibers/Phenolic Resin Composites

Fibre reinforced composites have become one sort of high-tech materials owing to their light weight, large specific strength and modulus, excellent thermal resistance, and high designability. Kevlar fiber is an organic fiber with high performance, and phenolic resin (PF) is an kind of thermosetting resin with outstanding mechanic property. Thus, composites based on Kevlar fibers and PF resin are expected to have more desirable performance. However, owing to the high curing temperature of PF resin, it has a bad effect on the mechanic property of composites, what’s more, the strength of PF resin’ condensate is too high, toughness is relatively low, so it can’t make a good balance between strength and toughness. The surface of Kevlar fibers has low chemical activity, few polar functional groups and smooth morphology, resulting in the poor interface bonding with the resin matrix, so it can’t be used in advanced polymer composites. Therefore, the aim of this thesis is to overcome above mentioned problem associated with Kevlar fiber/PF resin composites.Firstly, a reactive hyperbranched polysiloxane (HPSi) with-Si-O-Si-groups was designed and synthesized via the hydrolyzation of KH-550and water. HPSi was used to develop a novel high performance HPSi/PF resin, and the effect of HPSi content on the processing characteristics and properties of HPSi/PF resins were investigated intensively. The result shows that,through adding HPSi into PF resin, a cross-linking structure with good toughness was formed, and because of some phenyl appearing, its strength and toughness can be adjusted effectively; in addition, due to improved PF resin, its thermal property and dielectric properties.Secondly, focusing on the poor interface bonding with the resin matrix, we adopt phosphorous acid (PA) solutions to modify its poor interface bonding. The changes in the chemical structure, element composition, surface morphology and surface roughness of fiber surface were characterized to investigate the effects on the surface of Kevlar fibers. The result shows that, through phosphorous acid (PA) solutions, oxygen plasma can introduce a lot of oxygen-containing functional groups onto the surface of fiber, its surface became rough with apparent flute, improving interface bonding between fiber and resin.Finally, the effect of HPSi content on the interfacial property of composite was studied. It shows that, different HPSi content makes different properties of resin and different interface bonding, resulting in the different interfacial property of composites.