Preparation And Properties Of Rubber Nanocomposites

Rubber nanocomposites are materials that inorganic/organic nanoparticles (dispersed phase) are uniformly dispersed in rubber matrices (continuous phase). Because of the small size effect, surface effect, quantum size effect and micro-quantum tunnel effect of the nanoparticles, rubber nanocomposites exhibit markedly improved microstructures, properties and applications when compared to traditional rubber composites. Rubber nanocomposites represent a new alternative to prepare high-performance and multifunctional composites. In this paper, fibrillar nanofillers, layered nanofillers, granular nanofillers, inorganic functional composite nanofillers and polymeric nanofillers were employed to prepare rubber nanocomposites which are used in the fields of tire tread, multifunctional materials and sealing materials. The relationships between microstructure and properties of rubber nanocomposites were systematically studied. The main contents and conclusions are as follows:Natural rubber nanocomposites reinforced with fabrillar silicate attapulgite (AT) were prepared by mechanical compounding. Silane coupling agents and quaternary ammonium salts were employed as modifiers to improve the compatibility between AT and the rubber matrix. The results show that the modified AT and natural rubber were compatible. The disaggregation and orientation of AT needles and the strong rubber/filler interfacial interactions are crucial for the reinforcement of AT on the rubber matrix. The application of tetrapod-like zinc oxide whisker (T-ZnO_w) and nano-zinc oxide (N-ZnO) instead of conventional zinc oxide (O-ZnO) in tire tread was investigated. An obvious synergistic effect could be observed when T-ZnO_w and N-ZnO were collaborative applicated due to the anchoring effect of T-ZnO_w and the nanometer effect of N-ZnO. On this basis, carbon black (CB), AT, T-ZnO_w and N-ZnO were collaborative employed to reinforce the tire tread. Combinding with the investigation of filler dispersion status, rubber/filler interfacial structure and filler network of the nanocomposites, the synergistic reinforcing mechanism of multiphase fillers on the rubber matrix were clarified. The results show that the curing properties, mechanical properties, thermo oxidative resistance, abrasion resistance, cold resistance and wet skid resistance of the nanocomposites were significantly improved. What is more, the rolling resistance and heat build-up of the nanocomposites were reduced.Intercalated/exfoliated natural rubber/organo-montmorillonite (OMMT) nanocomposites were prepared by mechanical compounding. The microstructures and properties of the nanocomposites were investigated and clarified. The results indicate that the introduction of OMMT not only accelerated the curing process but also increased the crosslinking density of the nanocomposites. The microstructure evolvement of OMMT was influenced by the curing process parameters. The mechanical properties, dynamic mechanical properties, thermal stability, oil resistance were dramatically improved by the addition of a small amount of OMMT. Furthermore, CB and OMMT were employed simultaneously to reinforce the tire tread. The results demonstrate that the dispersion and intercalation of OMMT layers were promoted by CB nanoparticles. At the same time, OMMT layers exhibited a partition effect on the CB filler network. The synergistic reinforcement of OMMT and CB in the nanocomposites can be attributed to the formation of CB/OMMT hybrid filler network. Despite possessing higher rolling resistance and heat build-up, the tire tread containing CB and a small amount of OMMT exhibited enhanced mechanical properties, thermo oxidative resistance, abrasion resistance, thermal stability, solvent resistance, cold resistance and wet skid resistance.Natural rubber nanocomposites reinforced with nanobarite (NB) were prepared by mechanical compounding. The results show that the NB modified by sodium aluminate and sodium stearate (SA-Al₂O₃-NB) exhibited outstanding reinforcement due to its homogenous dispersion in the rubber matrix and the strong rubber/filler interactions. Furthermore, the microstructure and properties of the tire tread containing both SA-Al₂O₃-NB and CB were investigated. The results show that SA-Al₂O₃-NB and CB could be uniformly dispersed in the rubber matrix and a special hybrid filler network could be constructed. The mechanical properties, thermo oxidative resistance, abrasion resistance and corrosion resistance were obviously improved. The dynamic mechanical analysis results indicate that the tire tread possesses good wet skid resistance, rolling resistance and heat build-up properties. The pilot scale experiment was carried on based on the laboratory results and hence the high-performance tire tread and retreated tires were obtained.The AT-CeO₂ and AT-Fe₃O₄ composites nanoparticles were prepared by coprecipitation technique in the aqueous suspension of AT. AT-CeO₂ and AT-Fe₃O₄ were fistly modified by hexadecyl trimethyl ammonium bromide (CTAB) and then were used as fillers to prepare natural rubber/styrene butadiene rubber nanocomposites. The results show that the CeO₂ nanoparticles, with a diameter of about 5nm, were absorbed to AT needles'surfaces. CeO₂ nanoparticles enhanced the disaggregation of AT needles during the compounding process. Combinding with the dispersion strengthening of CeO₂, the reinforcement of CTAB-AT-CeO₂ on the rubber matrix was better than that of CTAB-AT. At the same time, the thermal stability and miscibility of the rubber/CTAB-AT-CeO₂ nanocomposites were also improved. The results also show that the as-obtained Fe₃O₄ nanoparticles, with a diameter of about 10nm, exhibits apparent superparamagnetism at room temperature. CTAB-AT-Fe₃O₄ composites nanoparticles also play an obvious reinforcement on the rubber matrix, and hence the multifunctional rubber nanocomposites with both good mechanical properties and superparamagnetism were obtained.Rubber composites based on ethylene propylene diene monomer (EPDM) and electron beam irradiated polytetrafluorethylene (PTFE) micro-/nano- particles were prepared by mechanical compounding. The curing characteristics, morphologies, mechanical properties, abrasion behaviors, permanent compression set and thermal degradation behavior of the composites were investigated. The results show that, in comparison with the PTFE microparticles, the PTFE nanoparticles enhanced the lubrication of EPDM composites and delayed the curing process due to it extremely low friction coefficient, larger specific surface area and higher concentration of carboxyl group on the surfaces. It's evident that the mechanical properties of EPDM/PTFE nanocomposites were improved due to the nanometer particle dimension and good dispersion of PTFE nanoparticles as well as the efficient interfacial bonding between rubber and PTFE nanoparticles. The particle size, isotropy and the interactions between EPDM and PTFE particles were crucial to the permanent compression set of the EPDM/PTFE nanocomposites. The thermal degradation of the EPDM/PTFE nanocomposites was devided into two stages. However, in comparison with the PTFE microparticles, the PTFE nanoparticles promoted the thermal degradation of EPDM.