Study On Modification Of Benzoxazine Resin By Nano - Core Shell Rubber And Toughening Mechanism

Benzoxazine resins is a kind of latest developed thermoset resins, which has been used in the field of aerospace, automotive and electronics with its good thermostability and dielectric properties, together with lightweight, high strength, and low water absorption. Furthermore, benzoxazine resins keep good compatibility with general resins, like phenolic resins, epoxy resins, bismaleimide resins. But in the mean time, poor toughness and high curing temperature limit their applications in industrial production. A large number of studies has been performed to solute these problems in recent years. In this paper, three kinds of commercialization of core-shell rubber particles were used to toughen benzoxazine. The effect of different diameter and core of core-shell rubber on thermal and mechanical properties, together with processability were studied, the effective toughening mechanisms were analysized, too. This paper aimed at preparing high performance resin with good comprehensive performance, and offering theoretical basis and reference for further study and industrial production.In this paper, Nano core-shell rubber (CSR) particles, styrene-butadiene/polymethyl methacrylate (CSRMX125), polybutadiene/polymethyl methacrylate (CSRMX156), and silicone/polymethyl methacrylate (CSRMX96o) were used to toughen Polybenzoxazine (PBa). Dynamic curing behaviors of benzoxazine/core-shell rubber composites were studied by non-isothermal differential scanning calorimetry (DSC). The result showed that the average activation energy and reaction order were increased while introducing CSR. The curing reaction rate was dually controlled by dynamic factors in the initial stage of crosslinking, but was mainly by diffusion in the latter stage.Thermal weight loss of cured PBa and PBa/CSR was measured by thermogravimetric analyzer (TGA). It show that the contents of CSR have hardly effect on thermal weight loss of PBa and PBa/CSR. The scanning electron microscope (SEM) confirmed the well dispersion of CSR in cured composite matrix. The fracture surfaces microtopography of CSR toughened PBa resins (PBa/CSR) were examined by scanning electron microscopy (SEM). It showed that nano CSR particles were well dispersed in matrix. Dynamic mechanical behaviors of resins were characterized by dynamic thermomechanical analysis (DMA). Storage modulus of PBa decreased and glass-transition temperature of PBa invariably in the presence of CSR. Storage modulus of PBa resins contained equal amount of CSR were as follow: PBa/CSR(MX125)> PBa/CSR(MX156)> PBa/CSR(MX960). Tensile property and fracture toughness of resins were measured by universal tester. It revealed that, when modified by CSR, tensile Young’ s modulus of resins decreased while tensile strength and fracture toughness enhanced, and flexural strength was nearly invariable. Tensile Young’s modulus and flexural Young’s modulus of PBa/5%CSR(MX125) were decreased by23.3%and21.7%respectively, and tensile strength was increased by24.4%. The fracture toughness of PBa/10%CSR(MX125) and PBa/10%CSR(MX156), in which average CSR particles size were100nm, were increased by56%and53%respectively compared with PBa. The toughening mechanisms of CSR(MX125) and CSR(MX156) modified PBa were plastic void growth, while CSR(MX960)(particle size is100-300nm) modified PBa were crack pining and crack deflection.