Studies On The Ablation Mechanisms Of HNBR Composites And Surface Modification Of Rubber To Lower Friction

Hydrogenated nitrile butadiene rubber (HNBR), prepared from nitrile butadiene rubber (NBR) by hydrogenation, has good thermal stability due to the backbone of saturated hydrocarbon structure, and is a new rubber material appeared in recent years with excellent combination properties. The flexible anti-ablation materials, based on HNBR, were prepared for the first time. It was studied that the effects of types of filler, fumed silica (FS), organically modified montmorillonite (OMMT) and expanded graphite (EG), on the ablative performance of HNBR composites. HNBR/OMMT composite with the lowest linear ablation rate and the largest mass ablation rate does not tend to carbonization. Conversely, the HNBR/EG composite with the highest linear ablation rate and the smallest mass ablation rate is prone to carbonization. Ablative performances of HNBR/silica composite are between the two. Different composites and char layers were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS) and wide angle X-ray diffraction (WAXD). Based on these results, it was discussed that the effects of types of filler on the ablation mechanisms of HNBR composites.Due to the high surface friction coefficient of rubber materials, a significant amount of heat can be produced when relative motion happens between workpiece and rubber sealing goods in some cases of dynamic sealing, which shortens the service life. So it is of great importance to lower the friction of rubber surface. In the article, it was done that research on the surface modification of ablation resistance HNBR composites and oil resistance NBR composites to lower friction. Main contents are as follows:1. It was studied that surface modification of ablation resistance HNBR composites by coating containing fluoride. Results indicated that surface contace angles of composites decrease dramaticlly by plasma treatment before coating, which is in favor of spreading of coating on the surface and improve the quality of coating. So the effect to reducing the firction of coating is enhanced significantly.2. Efforts to lower the friction of NBR composites was done by coating containing fluoride. The best spray process was found. And it was examined that the effect of different post-processings, such as air drying, plasma treatment and heating at 150℃, on the friction properties of coating. The results of friction tests showed that the effect of post-processings on friction properties of coating is marked. The coating treated by heating, with the best comprehensive properties, can keep friction coefficient at a low level steadily all the time. To understand the reasons leading to the difference between friction performances of coatings, surfaces with and without abrasion were analyzed by FTIR, scanning electron microscope (SEM) and energy dispersed X-ray spectroscope (EDS).3. Primarily study on plasma fluorination deposition on rubber surface was done. Results of FTIR and X-ray photoelectron spectroscopy (XPS) illustrated that fluorine element appeared on the rubber surface after CF4 plasma treatment. And friction coefficient of NBR lowered observably by fluorinated modification.