Effect Of Two-Dimensional Reactive Liquid Nano-Reinforcement On Barrier And Mechanical Properties Of Epoxy Composites

With unique two-dimensional nano lamellar structure, montmorillonite (MMT) and graphene oxide (GO) were widely used as the reinforcement to improve the mechanical and barrier properties of composites. However, the obstacles needed to be overcome were the spontaneously aggregated tactoid layer-structure of MMT/GO and their distinctively poor interfacial adhesion with polymeric resins. In this paper, kinds of liquid nano-reinforcement containing activated MMT/GO were prepared by using ultrasonic treatment. The dispersion uniformity and interfacial adhesion of activated MMT/GO in epoxy matrix were investigated, and then the mechanical and barrier properties of epoxy composites with activated MMT/GO were characterized.The preparation methods of liquid nano-reinforcement containing activated MMT/GO were studied, and their structure and dispersion were also characterized. The activated MMT/GO were prepared by intercalating butyl glycidyl ether (BGE) into the inter-layer surfaces of nano-sheets under ultrasonication, and in a form of liquid nano-reinforcement. It showed advantages of low viscosity, high chemical reactivity, excellent dispersibility and interfacial compatibility in epoxy matrix.The enhancements in mechanical and barrier properties of epoxy composites with activated MMT/GO were studied. According to the results of mechanical properties test, the enhancements in tensile and flexural properties of epoxy composites confirmed the strong interfacial adhesion between activated MMT/GO and epoxy matrix. With the addition of 3 wt.% of activated MMT, the tensile strength and modulus of epoxy composites were enhanced by 22.4 and 60.9%, the flexural strength and modulus were enhanced by 11.6 and 38.0%, respectively, in comparison with those values for the neat epoxy. Similarly, with the addition of 1.5 wt.% of activated GO, the tensile strength and modulus of epoxy composites were enhanced by 45.7 and 78.3%, the flexural strength and modulus were enhanced by 21.1 and 49.6%, respectively. Due to the uniform dispersion of activated MMT/GO in the epoxy matrix, the barrier properties of epoxy composites were also significantly enhanced. According to the results of barrier properties test, compared with the neat epoxy, the diffusion coefficient of epoxy composites with 3 wt.% activated MMT was decreased as much as 96.6%, the diffusion coefficient of epoxy composites with 1.5 wt.% activated GO was decreased 86.8%.Based on Fick’s second law and Langmuirian theory, a schematic model was proposed to illustrate the process of moisture diffusion in epoxy composites with activated MMT/GO. According to the experimental results and theoretical analysis, the exfoliated nano-sheets were uniformly dispersed in the matrix, their two-dimensional lamellar structure with large aspect ratio would extend the effective penetration path of water molecules into tortuous forms, thus reduced the diffusion coefficient of small molecules and enhanced the barrier properties of composites.