A quantitative approach to study the interface of carbon nanotubes/elastomer nanocomposites

Effect of Prestrain on Payne Effect and Hysteresis Loss of Carbon-Black-Filled Rubber Vulcanizates: Measurements and Modeling

The performance of a viscoelastic damper is governed by the mechanical properties of the viscoelastic material, which are sensitive to prestrain. Among viscoelastic materials, carbon black (CB)-filled rubber vulcanizate is commonly used in structural applications. In this paper, the prestrain-dependent Payne effect and hysteresis loss of CB-filled rubber vulcanizates are investigated through experimental and theoretical analysis. Based on the experimental results, the classic quantitative models proposed by Kraus, Huber-Vilgis, and Maier-Göritz are used to describe the Payne effect. The results show that the Maier-Göritz model is most suitable to describe the Payne effect, especially for the loss modulus. After calculating the area of the hysteresis loops, hysteresis loss curves at various dynamic strain amplitudes are parallel to each other. Through application of the time-strain superposition principle, the hysteresis loss at any arbitrary prestrain can be predicted. Thus, the aim of this paper is to provide guidance for researchers in choosing an accurate model for future investigations of the prestrain-dependent Payne effect. An accelerated characterization method is useful for the prediction of the hysteresis loss of rubber products using small amounts of experimental data, which can provide manufacturers with more attractive and lower cost opportunities for testing the mechanical properties of rubber products.

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.

Sulfur-Modified Carbon Nanotubes for the Development of Advanced Elastomeric Materials

The outstanding properties of carbon nanotubes (CNTs) present some limitations when introduced into rubber matrices, especially when these nano-particles are applied in high-performance tire tread compounds. Their tendency to agglomerate into bundles due to van der Waals interactions, the strong influence of CNT on the vulcanization process, and the adsorptive nature of filler-rubber interactions contribute to increase the energy dissipation phenomena on rubber-CNT compounds. Consequently, their expected performance in terms of rolling resistance is limited. To overcome these three important issues, the CNT have been surface-modified with oxygen-bearing groups and sulfur, resulting in an improvement in the key properties of these rubber compounds for their use in tire tread applications. A deep characterization of these new materials using functionalized CNT as filler was carried out by using a combination of mechanical, equilibrium swelling and low-field NMR experiments. The outcome of this research revealed that the formation of covalent bonds between the rubber matrix and the nano-particles by the introduction of sulfur at the CNT surface has positive effects on the viscoelastic behavior and the network structure of the rubber compounds, by a decrease of both the loss factor at 60 °C (rolling resistance) and the non-elastic defects, while increasing the crosslink density of the new compounds.

The Role of Interfacial Interactions on the Functional Properties of Ethylene-Propylene Copolymer Containing SiO2 Nanoparticles

In this paper, the mechanical properties, thermal stability, and transparency of ethylene-propylene copolymer (EPC) elastomer modified with various weight percentages (1, 3, and 5 wt.%) of SiO₂ nanofillers have been studied. The nanocomposites were prepared via a simple melt mixing method. The morphological results revealed that the nanofillers were uniformly dispersed in the elastomer, where a low concentration of SiO₂ (1 wt.%) had been added into the elastomer. The FTIR showed that there are interfacial interactions between EPC matrix and silanol groups of SiO₂ nanoparticles. Moreover, by the addition of 1 wt.% of SiO₂ in the EPC, the tensile strength and elongation at break of EPC increased by about 38% and 27%, respectively. Finally, all samples were optically transparent, and the transparency of the nanocomposites reduced by increasing the content of SiO₂ nanoparticles.

Necessity of two-dimensional visualization of validity in the nanomechanical mapping of atomic force microscopy for sulphur cross-linked rubber

The importance of the two-dimensional (2D) visualization of validity for nanomechanical mapping in atomic force microscopy (AFM) for sulphur cross-linked rubber is emphasized for accurately interpreting the nanoscale physical properties on the surface of the soft material. The “R-factor,” evaluated to be the difference between the experimental and theoretical force–deformation curves, was considered to be the reliability index of the AFM analysis for all data points on the sample surface. A small R-factor corresponds to high accuracy. The advantage of the R-factor mapping method is demonstrated using nanomechanical mapping data of the inhomogeneous isoprene rubber network by the Johnson–Kendall–Roberts and the Derjaguin, Muller, and Toporov contact mechanics models. The 2D R-factor mapping clearly and correctly supported the roles of sulphur cross-linking reagents to control the network morphology of vulcanizates. Additionally, the blanket effect, which is induced by the rubber layer on the hard part and influences experimental force–deformation curves, is firstly proposed in this study. Nanomechanical mapping with 2D reliability indexes is expected to contribute to an advance in AFM studies on soft matter such as rubber materials, leading to a more accurate understanding of the structural characteristics of the rubber networks. Thus, this validity confirmation method is necessary for developing rubber science and technology.

The two-dimensional visualization of validity for nanomechanical mapping in atomic force microscopy for sulphur cross-linked rubber is emphasized for accurately interpreting the nanoscale physical properties on the surface of the soft material.