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Abstract. Novel blends of acrylonitrile butadiene rubber (NBR) and polyurethane-silica (PU-SiO 2 ) hybrid networks have been prepared by melt blending. The PU-SiO 2 hybrid networks were formed via the reaction of NCO groups of NCO-terminated PU prepolymer and OH groups of SiO 2 in the absence of an external crosslinking agent (i.e. alcohols and amines) during the curing process of NBR. Both in the neat PU-SiO 2 system and the NBR/(PU-SiO 2 ) system, the NCO-terminated PU prepolymer could be crosslinked by SiO 2 to form PU-SiO 2 hybrid networks. The effects of PU-SiO 2 introduction into the NBR, on the properties of the resulting blends were studied. It was found that the vulcanization was activated by the incorporation of PU-SiO 2 . Transmission electronic microscopy (TEM) studies indicated that the interpenetration and entanglement structures between NBR and PU-SiO 2 increased with increasing PU-SiO 2 content and the quasi-interpenetrating polymer networks (quasi-IPN) structures were formed when the PU-SiO 2 was 50 wt% in the NBR/(PU-SiO 2 ) systems. The microstructures formed in the blends led to good compatibility between NBR and PU-SiO 2 and significantly improved the mechanical properties, abrasion resistance and flex-fatigue life of the blends.

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Graphene nanosheets are prepared by solution‐phase exfoliation of graphite and successfully incorporated with polyimide to obtain polyimide/graphene (DABPI/G) nanocomposites via in situ polymerization. Compared with those of pure DABPI, the DABPI/G nanocomposites exhibit better barrier and thermal properties. The oxygen and water vapor transmission rates of the DABPI/G (0.5 wt%) nanocomposite are 0.69 cm3 m−2 d−1 and 0.44 g m−2 d−1, respectively, which are 92 and 85% lower than those of pure DABPI. Meanwhile, the DABPI/G (0.5 wt%) nanocomposite exhibits excellent thermal stability with a Td5% of 578 °C and a coefficient of thermal expansion of −0.19 ppm K−1. The excellent barrier and thermal properties of DABPI/G nanocomposites are mainly attributed to the fine dispersion and orientation of the graphene nanosheets, increased crystallinity, and low free volume of the DABPI matrix. These are the result of the “dual‐plane” structure effect, which is the synergistic orientation effect between the rigid planar molecular chains of DABPI and the nanosheets of graphene.