Journal of Rubber Research最新文献

The mechanical properties of EB-irradiated natural rubber (NR) composites were improved by a synergistic effect of adding silica (SiO₂) and graphene nanoplatelets (GE) mixture into NR matrix, reported in a previous work. In this study, dynamic mechanical analysis (DMA) was performed, from which volume resistivity and degradation properties were determined. Latex NR compound filled with SiO₂/GE mixture was cured by EB irradiation to form NR composites. SEM images and the EDXS elemental mapping indicated good dispersion of GE and SiO₂/GE in the NR matrix. The DMA showed that the storage moduli of NR composites filled with fillers were higher than that of NR_-EB. Using 2.5 phr of fillers, which is below the percolation threshold, volume resistivity properties of all NR composites remained unchanged relative to the pure NR and with varying EB doses in the range of 100–250 kGy. Finally, it was found that adding fillers into NR composites caused a decrease in water absorption of irradiated NR composite at 70 °C and a relative humidity of 80%. According to the authors’ previous work and the present results, this novel NR composites showed a potential in devices related to high-voltage application requiring electrical insulation with enhanced mechanical properties.

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Cars are the most important mode of transportation and play a significant role in the development of modern communities. Tyres, one of the main components of cars, hold strategic importance. Therefore, research aimed at improving the quality and increasing the production speed of tyres is an integral part of the strategic policy on this subject. In this study, the effects of pressing time in curing press (time of curing with pressure) on the structural properties of radial tyre tread were investigated. According to the one-factor response surface methodology, 10 samples that had different pressing times during their curing press were produced. The swelling test was used to study the cured compound structure. In this way, essential parameters such as diffusion coefficient and crosslinking density were calculated. The results showed that the vulcanised samples in free pressure conditions had the lowest amounts of crosslinking density. Also, these samples had the highest intrinsic diffusion coefficient. It is also observed that the intrinsic diffusion coefficient and crosslinking density have a relationship with pressing time. Mechanical tests were also performed to determine the dependence of the mechanical properties of the tyre tread on the duration of pressing time. As an obvious result, the cured samples in zero-pressure conditions had the lowest tensile strength, tear strength, hardness and the highest amount of resilience percentage. However, the abrasion parameter had the most negligible dependence on the pressing time. The results showed the dependence of the swelling and mechanical properties of the tread tyre compound on the pressing time. So, according to the optimal targeting for different variables and results, the optimal time of applying pressure during curing for the tyre tread compound has been obtained. As an important result, in the curing process, the pressurising can be stopped after about 14 min while the curing continues only with heat.

Ceramic membranes are considered more effective for wastewater treatment applications than polymeric membranes because of their excellent resistance to thermal and chemical environments and possess high durability. To avoid the high cost of commercial ceramic membranes, recently, a significant improvement has been accomplished in developing them using low-cost alternative materials and their application in wastewater treatment. This study investigated the performance of an innovative ceramic microfiltration (MF) membrane fabricated with inexpensive Fuller's earth clay in treating the natural raw rubber (ribbed smoked sheet)-processing wastewater. The flat sheet low-cost membrane used in this study was prepared by uniaxial dry pressing route, followed by sintering at 850 °C, and it possessed 39% porosity with 0.176 µm pore size. The wastewater was treated in dead-end filtration mode at different pressures varying from 0.35 to 2 bar and observed the percentage removal of COD, turbidity, and total suspended solids (TSS). Untreated wastewater had a turbidity of 150 NTU, 1200 mg/L TSS, and 10,800 mg/L COD. At a low operating pressure of 0.35 bar, 94% removal of turbidity and total suspended solids was obtained. Also, significant COD removal of 70.4% from wastewater was obtained using the prepared low-cost MF membrane. Finally, the fouling phenomenon during the wastewater treatment was analyzed and it was concluded that it followed the cake filtration model. For future work, cross-flow filtration of wastewater using fabricated Fuller's earth clay ceramic membrane is recommended as it could pave the way forward towards commercialization and wide-scale industrial applications.

Conventional manufacturing techniques of natural rubber foam (NRF) require long processing time besides producing closed cell structure, a property that limits the application of the NRF. The NRF produced via compression moulding (CPM) and microwave-convection oven heating techniques were compared in this study. The correlation between different processing techniques with the physical, morphological, and acoustic properties of NRF was examined. The results indicated that in all the processing techniques, an increase in the blowing agent (BA) led to a decrease in the density of the NRF. Heating the material sequentially with 16 parts per hundred (phr) of BA in a microwave oven at 1000 Watts, and then, in a convection oven at 150 ℃ produced NRF with a density of 0.23 g/cm³. In contrast, the NRF produced by CPM with 16 phr of BA had a density of 0.35 g/cm³. Scanning electron microscope analysis revealed that the NRF generated by CPM had fewer interconnected and more closed cells. On the other hand, sequential heating using microwave and convection heating techniques and vice versa led to the production of NRF with more open and interconnected cells. The prepared NRF was examined for acoustic properties. The results showed that the NRF produced by CPM at 12 and 16 phr of BA had the lowest ability to attenuate sound wave energy. This was due to the highly solid surface of the sample, which caused high sound wave reflection. Open and interconnected cells significantly improved the acoustic efficiency. These findings indicated that microwave-assisted heating techniques can modify the cellular structure of NRF and produce the material within a shorter period.

Influences of silane coupling agent loading (e.g. 0–6%) on properties of sepiolite-filled natural rubber (NR) composites were investigated in this study. The amount of silane addition on properties of phenolic resin-crosslinked NR filled with sepiolite composite was optimised. A rheometer was used to evaluate the curing characteristics of the composites while morphological properties were studied by scanning electron microscopy. Fourier-transform infrared spectrometer, temperature scanning stress relaxation, and Mooney–Rivlin model were used to assess the interactions between sepiolite filler and rubber matrix, and the tensile properties and strain-induced crystallisation behaviour were investigated by tensile testing and wide-angle X-ray scattering, respectively. Incorporating a silane coupling agent reduced the size of sepiolite aggregates from ~ 0.4–10 to 0.4–5 μm and decreased filler–filler interaction as well as the curing time of the composite. The silane also improved adhesion between the filler and the rubber by the additional interactions between silane and sepiolite filler. These interactions slowed down the rate at which NR polymer molecules relax, increased tensile strength, and facilitated strain-induced crystallisation. The strongest interactions between filler and rubber, evidenced by maximal tensile strength that was 20% over the non-silanised NR composites, were attained at 4% silane coupling agent relative to the sepiolite by mass.

Filler hybridisation in elastomers has become a subject of both scientific and industrial interest. Consequently, the use of nanofillers has attracted researchers looking to enhance the performance of elastomers. Therefore, carboxyl graphene (CG) and silicon dioxide (SiO₂) nanofillers have been hybridised for the combined effect study of composite NBR (acrylonitrile butadiene rubber) elastomers in various accelerated environmental ageing conditions (high temperature, low temperature, and QUV). The inorganic filler (SiO₂) had enhanced dispersion upon hybridising with CG on the surface of a composite NBR elastomer. To evaluate the mechanical and dynamic mechanical properties, unfilled and filled (CG/SiO₂) composite NBR elastomer samples were prepared by mixing and rolling methods. Furthermore, the prepared samples were kept in various ageing chambers. The results of mechanical testing exhibited that tensile strength improvement was greater for filled elastomers than unfilled elastomers after ageing. Moreover, the filled elastomers were also able to retain the reduction in elongation at break after ageing. However, after ageing, the hardness of composite NBR elastomers increased marginally with the addition of CG/SiO₂. Moreover, the loss factor (tan δ) of a composite NBR elastomer (CG/SiO₂: 15/7.5), compared to that of the unfilled NBR elastomer before and after ageing, decreased but was still much higher than that of the aged unfilled NBR elastomer. The reason behind that was that CG/SiO₂ dispersion in the composite NBR elastomer matrix acted as a barrier against ageing. CG/SiO₂ hybridising is an effective way to develop high-performance composite NBR elastomers with good potential in industrial applications.

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The slip casting of ceramics uses synthetically prepared water-soluble polymers and polymer emulsions as binder to achieve adequate yield stress of the consolidated body and high green strength. Substitution of synthetically prepared binders with a naturally renewable one is highly recommended for environmental friendliness and sustainability. Herein, slip casting of aqueous alumina slurries using natural rubber latex (NRL) binder is studied for the first time. Slurries of high alumina loading (40–55 vol%) at rubber concentrations in the range of 2–8 wt% obtained by mixing a concentrated aqueous alumina powder dispersion and a concentrated NRL exhibit viscosity and yield stress suitable for slip casting. The thickness of the body produced in 1 h from the slurries containing the NRL binder by slip casting in a plaster of Paris mold is three times higher than that produced from a slurry prepared using 2 wt% polyvinyl alcohol (PVA) binder. The slip-cast green bodies after annealing at 200 °C show high strength (3–9.68 MPa) due to cross-linking of rubber. Sintered ceramics prepared from the slip-cast bodies exhibit ~ 97% theoretical density (T.D) with an average grain size of 1.8 μm. NRL binder-based slip casting is capable of producing sintered alumina crucibles of wall thickness as low as 1.2 mm. NRL can be an eco-friendly and sustainable candidate binder for the slip casting of ceramic materials.