| Glass fiber reinforced polybutylene terephthalate（GF/PBT）composites are widely used in the fields of electronics,automotive and machinery industry due to excellent properties.The performance of glass fiber composites is closely related to the interface,a good interface can significantly improve the comprehensive performance of composites.However,glass fiber is an inorganic material with poor compatibility with the resin matrix,which greatly affects the composite performance.In order to improve the interfacial strength of fiber and resin,enhance the mechanical properties of GF/PBT composites and broaden the range of applications,sizing agents are usually sized on the surface of glass fibers.The film former are the key components of sizing agents and have a significant impact on performance of the sizing agents.Epoxy resin film former have excellent performance,are widely used,and have broad development prospects.Therefore,the research focuses on the study of a waterborne epoxy resin film former for GF/PBT composites.（1）An epoxy resin modified copolymer E-P105 was obtained by reacting block copolymer P105 with epichlorohydrin（ECH）.The structural characterization by FTIR spectroscopy,and the optimal reaction conditions were determined by measuring the variation of epoxy value:the molar ratio of ECH to P105 was 1.5:1,the molar ratio of NaOH to P105 was 1.2:1,the amount of catalyst Sn Cl4 was 0.6%of the mass of P105,the ring-opening temperature was 80℃,reaction time was 2.5 h.The ring-close temperature was 60℃,reaction time was 1.5 h.（2）The hydrophilic epoxy resin was obtained by grafting and chain expansion of E-P105 with epoxy resin E-51 and bisphenol A,meanwhile,bisphenol A and epoxy resin E-51 were expanded to form high molecular weight epoxy resin by addition reaction,and then waterborne epoxy resin emulsions were made by using the phase inversion method.The optimal preparation process was determined by testing the particle size and stability of the epoxy resin emulsion.When the molar ratio of epoxy resin E-51 to bisphenol A was2.25∶1,the amount of E-P105 was 20%of the total mass of E-51 and bisphenol A,the amount of catalyst was 0.08%of the mass of E-51,the reaction temperature was 150℃,the reaction time was 1 h,and the emulsification temperature was 60℃,the waterborne epoxy resin emulsion was produced with small particle size and narrow distribution and good stability.（3）The self-made epoxy resin emulsion and commercial epoxy resin emulsion were separately used as film former to prepare sizing agents.Then,the glass fibers were sized,the sized glass fibers and PBT were prepared into GF/PBT composites.By comparing the mechanical properties such as tensile strength,flexural strength,and impact strength,as well as the color difference of GF/PBT composites treated with the two film formers,it was found that the mechanical properties of GF/PBT composites treated with the two film formers were similar,and the appearance color was almost identical.SEM analysis of fiber morphology revealed that a continuous and dense coating was formed on the fiber surface by the sizing agent,which effectively protected the fiber.（4）The effects of oil to water mass ratio,amount of emulsifier and temperature on the interfacial properties and interfacial tension of waterborne epoxy resin emulsion system were simulated by dissipative particle dynamics.The results showed that the system changed from oil-in-water state to water-in-oil state as the oil to water mass ratio decreased,and the interfacial tension increased,then stayed the same,then decreased,the particle size of the emulsion and interfacial tension decreased with the increase in the number of emulsifier parts,and in addition the interfacial tension decreased with the increase in temperature. |
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