In this paper, rigid polyurethane foams that were filled with expandable graphite (RPUF/EG) composites were prepared by the liquid blending method, and then the structure and flame retardancy performance of materials were investigated through optical microscope, scanning electron microscope, limit oxygen index, cone calorimeter, thermogravimetric analysis coupled to fourier transform infrared spectrum, and X-ray photoelectron spectroscopy. The results showed that a large number of EG could be good to the exhibition of flame retardancy of RPUF, where the optimal material was found at loading 15 phr EG that showed an increased limit oxygen index value and a decreased calorific or fuming value. TGA coupled FTIR and XPS revealed that EG could disassembled before RPUF under heating treatment, and it could form a pyknotic and enahnced residual carbon layer on RPUF surface after the fire, which restricted the transfer of gas, like oxygen or heat into PU matrix, finally resulting in the promotion of flame retardancy of RPUF.

Improving the interfacial interaction between rubber and silica nanoparticles, and simultaneously reducing free sulfur and preventing migration and volatilization of a rubber vulcanizing agent, commercial sulfur compound aliphatic ether polysulfide (VA-7) was chemically attached to the silica surface to obtain a functionalized nanoparticle (silica-s-VA7). Functional nanoparticles can not only effectively crosslink rubber without sulfur as a novel vulcanizator, but are also evenly dispersed in the rubber matrix and improve the dispersion of the remaining pristine silica as an interfacial compatibilizer. In addition, the thicker immobilized polymer layer and prominent crosslinking density of SBR nanocomposites simultaneously demonstrate that the novel vulcanizing agent silica-s-VA7 gives rise to significant improvement on the rubber–filler interfacial adhesion on account of the covalent linkages of organic and inorganic interfaces between elastomer and nanofillers. We envisage that this strategy may provide a new avenue to implement high-efficiency design for a multifunctional rubber-vulcanizing agent through an organic and inorganic hybridization mechanism.