Fracture properties of natural rubber filled with hybrid carbon black/nanoclay

Testing of Rubber Composites Reinforced with Carbon Nanotubes

Carbon nanotubes (CNTs) have attracted growing interest as a filler in rubber nanocomposites due to their mechanical and electrical properties. In this study, the mechanical properties of a NR/BR/IR/SBR compound reinforced with single-wall carbon nanotubes (SWCNTs) were investigated using atomic force microscopy (AFM), tensile tests, hardness tests, and a dynamical mechanical analysis (DMA). The tested materials differed in SWCNT content (1.00–2.00 phr) and were compared with a reference compound without the nanofiller. AFM was used to obtain the topography and spectroscopic curves based on which local elasticity was characterized. The results of the tensile and hardness tests showed a reinforcing effect of the SWCNTs. It was observed that an addition of 2.00 phr of the SWCNTs resulted in increases in tensile strength by 9.5%, Young’s modulus by 15.44%, and hardness by 11.18%, while the elongation at break decreased by 8.39% compared with the reference compound. The results of the temperature and frequency sweep DMA showed higher values of storage and loss moduli, as well as lower values of tangent of phase angle, with increasing SWCNT content.

Effect of Nanoclay Filler on Fatigue Life of Natural Rubber/Styrene-Butadiene Blend

In this paper, the fatigue life of natural rubber (NR)/styrene-butadiene rubber (SBR) compound is evaluated experimentally. The parameters investigated are the NR, SBR, and nanoclay loading in the composition, strain amplitude, and the frequency of the fatigue test. Fracture surfaces of NR/SBR/nanoclay compound are investigated using scanning electron microscopy (SEM). The results show that by increasing NR and the nanoclay loading in the rubber composition, the fatigue life of the rubber increases. For the nanoclay, a threshold value exists beyond which the fatigue life of the rubber compound decreases. It is also observed that by increasing the test frequency, the fatigue life of the rubber compound decreased. Tensile, hardness, and dynamic mechanical thermal analysis (DMTA) tests were also performed to evaluate the mechanical and thermal properties of the compound. SEM results show that by increasing the strain amplitude, the test specimens fail softly, and the addition of nanoparticles roughens the fracture surface and increases the fatigue life.

Molecular dynamics study of natural rubber-fullerene composites: connecting microscopic properties to macroscopic behavior

Macroscopic and microscopic properties of fullerene (C₆₀)-cis-polyisoprene (cis-PI) composites at varying fullerene concentrations were investigated using atomistic molecular dynamics (MD) simulations over microsecond time scales. Results show that the introduction of fullerenes into a polymer matrix increases density, bulk modulus and heat capacity while thermal expansivity decreases. The presence of fullerenes slowed the diffusion of both C₆₀ and cis-PI. Moreover, increasing fullerene concentration results in ordering of the cis-PI chains at the cis-PI-fullerene interfaces and shrinking of bulk PI regions. Free energy calculations of fullerene dimerization suggest that fullerenes disperse at low and aggregate at high fullerene concentrations. Our multi-scaled analysis approach demonstrates the role of 'ordered' regions adjacent to the interface between cis-PI and fullerene in controlling the level of order and mobility of the cis-PI chains. The relationship between the microscopic behavior and the changes in mechanical and thermal properties are discussed. Our study is beneficial for further studies and development of advanced rubber technology for novel, cost-effective, material with very high stiffness and thermal endurance with optimizing conditions of filler contents.