Two series of benzoxazine (BOZ) based composites were prepared with graphene oxide (GO) and graphite via in situ intercalative polymerization. Based on isothermal and non-isothermal mode Differential Scanning Calorimetry results, BOZ with the addition of GO could not only decrease the cure temperature, but also increase the cure rate of BOZ. On the contrary, BOZ with the addition of graphite would delay the polymerization of BOZ monomer. It was hypothesized that carboxyl groups of GO acted as weak organic acid which accelerated the ring opening procedure. Interestingly, BOZ/GO composite with 1 wt% GO occupied the least time to form polymer networks, attributing to the catalytic effect and good dispersion of GO. Moreover, BOZ with 1 wt% content of GO had relatively higher glass transition temperature and char yield than those of the corresponding BOZ/graphite sample, which was due to relatively stronger intermolecular interactions between GO and BOZ.

The present study is to examine the effects of glass-to-rubber transition of resin matrix on the friction and wear characteristics of friction materials, in relation to different types of thermosetting resins. Dynamic mechanical thermal analysis and friction test results revealed that glass-to-rubber transition of thermosetting resins influenced significantly the friction and wear behavior of the composite materials. There was a significant increasing tendency in friction coefficient and wear rate values for all composites when braking temperatures increased to 200 or 250 °C, accompanying the resin matrix converted from glassy state to rubbery state.Highlights► Phenolic resin, polybenzoxazine resin and blend resins as binder matrix. ► Thermal transition influence tribological property for resin based friction material. ► Friction coefficient increased sharply when glass-to-rubber transition happened.

A series of novel graphene oxide (GO)/poly(acrylic acid-co-acrylamide) super-absorbent hydrogel nanocomposites were prepared by in situ radical solution polymerization. The effects of GO content on the chemical structure, morphology and miscibility of the hydrogels were studied. The swelling behaviors, swelling kinetics and pH-responsive behaviors of the hydrogels were also evaluated. Owing to the hydrogen bonds and possible covalent bonds between GO and polymer chains, relatively lower content (<0.30 wt%) of GO could be dispersed well in the polymer matrix and enhanced the intermolecular interactions between the components effectively. On the contrary, an excessive amount of GO might form large agglomerates and weakened the interfacial interactions, resulting in the micro-phase separation between the components. Furthermore, the swelling capacities and swelling rates of hydrogels went up with increasing GO loadings to 0.30 wt% and then decreased with further increasing GO loadings. It is worth noting that the hydrogel only containing 0.10 wt% GO exhibited significant improvement of swelling capacity in neutral medium, and could also retain relatively higher swelling capacities to a certain degree at acidic and basic solutions. Therefore, the as-prepared GO-based super-absorbent hydrogels might have potential applications in many areas, such as biomedical engineering, construction engineering and hygienic products.Graphical abstractHighlights► We developed graphene oxide (GO)-based hydrogels by in situ solution polymerization. ► GO could improve the swelling ratio of hydrogels at extremely low GO content. ► The swelling kinetics of composite hydrogels fitted the pseudo-second-order model. ► The composite hydrogels exhibited pH-sensitive behavior.