The Preperation And Performance Of The Butyl Rubber(IIR)/the Natural Rubber (NR) Composites

As the core of the concept of foundation-shock isolation, laminated rubber bearings are one of the most important seismic isolation devices to improve the seismic capacity of buildings and to reduce the loss of life and property caused by earthquake. Laminated rubber bearings are made of rubber layer and thin steel sheet layers which are stacked alternately. Currently, nature rubber which has tensile-induced crystallization property is the main choice of the material for the rubber isolators. However, the existing single rubber material can't be able to meet the necessary requirements of high strength, high elasticity, high damping property, low modulus and low compression set for the isolation bearings. Therefore, it is necessary and significant to design and prepare new kinds of rubber composites to meet the performance needs of isolation bearings.In this paper, we used a special process to blend the butyl rubber (IIR) which has excellent damping property and nature rubber (NR) with different proportions to obtained NR/?R composites. The microstructure and microscopic dispersion of the NR/?R composites were observed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM) and atomic force microscopy (AFM).The dynamic and static mechanical properties of the composites were studied through computer-controlled universal testing machine, dynamic mechanical analyzer (DMTA), rubber process Analyzer (RPA) and other instruments and equipment. The property of stress-induced crystallization was researched by high and low temperature tensile tester and Shanghai synchrotron radiation light source WAXD. Also, the effect of procuring for butyl rubber on the co-vulcanization and mechanical performance of the composites was investigated in this paper. A high content of isoprene isobutylene and isoprene block copolymer was synthesized to be as the compatibility agent for natural rubber and butyl rubber and its effect on microstructure, mechanical properties and dynamic mechanical properties of the composites was studied. The main results of the work are as follows:(1) When the butyl rubber added to nature rubber, the mechanical properties of which reduced with the increase of the butyl rubber components. However, for the NR/?R composites, the damping properties were improved and the damping temperature range was broadened, so the application of natural rubber in the damper areas was widened. Especially for NR/?R composites with ratio 90/10, tan? peak can reach 1.0 which increased by 18% compared with pure NR and the effective damping temperature range could be from -59.6? to -29.5? which moved to higher damping temperature about 10? compared with pure NR. Because the nature rubber has stress-induced crystallization characteristic, NR/?R composites also showed some crystallization properties.(2) NR/?R rubber composites with new compatibility agent (high isoprene content isobutylene and isoprene block copolymer) were successfully prepared in this study. The composites consisted of two phases including the NR phase and the IIR phase, and the interfacial compatibility of the composites was improved obviously compared with the ones with no compatibility agent. The new composites show much higher damping property than traditional ones and the tan? value can be increased by 120% at 200% strain, which largely expand the application scope of natural rubber damping products. The tensile strength of composites increased from 19.1MPa to 21.6MPa when added into 4phr compatibility agent, which increased by 13.1%. Therefore, the NR/?R rubber composites with new compatibility agent are expected to have important applications as a high performance damping material for rubber bearing.(3) The NR/?R composites were obtained with the new process that butyl rubber was pre-vulcanized 20 minutes at 140? condition, the mechanical strength of which was greatly improved compared with the ones with traditional process. For NR/IIR composites with ratio 70/30, the tensile strength of which was increased 8.0MPa that improved by 61% and the tear strength was increased by 33%.What's more, the dispersion of the composites was well improved. The influence of pre-curing process on damping properties was related to the component content of butyl rubber.