Large surface‐area microparticles of natural chicken eggshell were prepared and characterized to illustrate how such particles can improve the toughness of epoxy resins. A small amount of organic compounds, in particular proteins, were found to be present in the microparticles and beneficial to the enhancement of the mechanical properties of the epoxy resins. Scanning electron microscopic analysis of the rough fracture surfaces show that there are full of plastic deformation, voids, cavities, and debonding phenomena in the microparticle‐filled composites. Positron annihilation study indicates that the lifetime of τ3 o‐Ps varies and the corresponding intensity of I3 becomes weak with the increase of eggshell particle content, which indicates that there is a good interaction between the epoxy resin and the filling particles. This gives rise to significant improvement in the toughness of the filled resin. The impact strength of the epoxy resin composite reaches 16.7 kJ/m2 compared with 9.7 kJ/m2 of neat epoxy resin when the epoxy resin composite is filled with only 5 mass% eggshell particles. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

The effects of SiO 2 nanoparticles on the performance of carboxyl-randomized liquid butadiene-acrylonitrile rubber (CRBN) modified epoxy resin (EP) nanocomposites were studied. With the addition of an appropriate amount of SiO 2 (2%) to EP/CRBN (95/5), the nanocomposites could achieve the desired impact strength and modulus. The morphology of the nanocomposites was studied with scanning electron microscopy and transmission electron microscopy. The nanocomposites showed a three-phase system; both the rubber particles and SiO 2 nanoparticles showed uniform dispersions in the EP matrix, with their phases all nanosized. A good correlation between the free-volume hole radius and mechanical properties was found. The introduction of a small amount of nanoparticles (both rubber and SiO 2 ) into EP led to the formation of interactions between the EP and nanoparticles. The interactions restricted the segment motion and the mobilization of the EP chains and then reduced the free-volume concentration in the amorphous region of EP. The fact that the average free-volume hole radius of EP/CRBN was larger than that of pure EP was mainly attributed to the contribution of the larger size of the free-volume holes within the rubber phase.

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