IntroductionNR is one of the most important nature polymers, which is widely used as the elastomeric matrix of various materials, including conveyor belts, sealing rings, tires, etc. In order to meet the requirements of the use of tires, NR composites must have the following two properties: (1) good mechanical properties, in order to undergo cyclic loading and strains in actual use, (2) good thermal conductivity and electrical conductivity, in order to export the heat or static electricity effectively and timely. However, traditional fillers (such as carbon black, silica, alumina, etc.) cannot improve both aspects simultaneously, though the high surface carbon blacks may improve both mechanical properties and electrical conductivity, but the precondition is that a relative large amount of high surface carbon black must be added, this may adversely affect the processing performance of the composites. Recently, the carbon nanotubes (CNTs) have become a hot spot in various research fields for their unique structure and outstanding performances [1,2]. High mechanical properties (tensile strength is 50 GPa, Young modulus is ~5 TPa) and good conductivity (electrical conductivity is ~10 7 s/m, thermal Abstract. Multi-walled carbon nanotubes (MWCNTs) were functionalized by polydopamine (PDA)-coating and mixed with natural rubber (NR) via latex compounding. Compared with pristine MWCNTs, the surface of MWCNT-PDA was covered by an amorphous and nanometer-scale PDA layer which had a large amount of oxygenic and nitric functional groups. So the MWCNT-PDA showed a perfect dispersion in NR matrix. The tensile strength of NR/MWCNT-PDA (5 phr) composites is 28.6 MPa, compared with the pure NR, which increased by 42%. For the electrical properties, when the content of MWCNT-PDA or MWCNTs is 2 phr, the volume resistivity of NR/MWCNT-PDA composites falls to about 2.7·10 9 Ω·cm, compared with 3.3·1013 Ω·cm of NR/MWCNT composites. The thermal conductivity of NR composites increased only by 28.2% when 5 phr MWCNT-PDA was added. A model proposed by Nan was used to calculate the thermal conductivity of NR/MWCNT composites, and the calculated values were compared with the experimental values, the results showed that the interface thermal resistance is the main reason why MWCNTs could not significantly increase the thermal conductivity of natural rubber.

Natural rubber (NR) and butyl rubber (IIR) blends were compatibilized by isobutylene-isoprene block copolymer (IIBC) which was specifically synthesized with a relatively high content of isoprene (14.5% mole fraction). Aiming at high damping elastomers, the IIR acts as the high damping phase dispersed in the natural rubber (NR) matrix in this blend. The morphology and microstructure was characterized by atomic force microscope (AFM) and transmission electron microscope (TEM). The results indicated that the IIBC as a compatibilizer could greatly increase the interfacial thickness. Damping property was studied by dynamic mechanical thermal analyzer (DMTA) and rubber processing analyzer (RPA). The results showed that the loss factor greatly increased with adding IIBC, and this may be due to the improved stress transfer promoting the IIR phase to deform and then dissipate energy. The tensile test demonstrated that the tensile strength and modulus increased when 4 parts per hundred rubber [phr] of IIBC was added. Finally, the NR and new NR/IIR isolation bearing samples were prepared and tested on a pressure shear testing machine that could simulate the actual situation during an earthquake. The results showed that hysteretic loss (for one cycle) of the new NR/IIR sample is 83% higher than that of the NR sample, rendering the compatibilized blends potential in isolation rubber bearings application.

Abstract. Brominated isobutyl-isoprene rubber/clay nanocomposite (BIIRCN) and ethylene-propylene-diene-monomer rubber/clay nanocomposite (EPDMCN) were prepared by melt blending. The micro-structural evolution of these two kinds of rubber/clay nanocomposites (RCNs) with vulcanization process was investigated using wide-angle X-ray diffraction (WAXD) and transmission electron microscope (TEM). The WAXD results revealed that the intercalated structure of organically modified clay (OMC) changed throughout the whole curing process. The intercalated structure kept on changing beyond the vulcanization stage of T 90 . The interlayer space of intercalated silicate in uncured BIIRCN is larger than that in uncured EPDMCN. However, the intercalated structure for EPDMCN changed by a larger extent than that for BIIRCN during the vulcanization process, and the interlayer space of the intercalated structure is larger in the cured EPDMCN than that in the cured BIIRCN. It was found that the intercalant (i.e., octadecylamine, ODA) for OMC could shorten the scorch time of the curing reaction, and increase the curing rate, which was attributed to the further intercalation during vulcanization. TEM results indicated that the spatial distribution of OMC is much better in BIIR (a polar rubber matrix) than that in EPDM (a non-polar rubber matrix). The changes in spatial dispersion structure during vulcanization for EPDMCN and BIIRCN show different trends. In conclusion, the polarity of the rubber is the determining factor influencing the evolution of both the intercalated structure and the spatial dispersion of clay during vulcanization.

No abstract

No abstract