Journal of Rubber Research最新文献

The preparation of epoxidised natural rubber (ENR) latex-dipped film was successfully carried out. The effects of several parameters, such as sulphur loading, vulcanisation temperature and time, leaching temperature and time, thickness, oil, and chemical resistance, were studied. ENR latex films were successfully prepared by varying the sulphur loading from 0.5 phr to 2.0 phr. Superior tensile properties were observed for the vulcanised temperature at 75 °C with vulcanisation at 30 min. A longer leaching time and higher leaching temperature demonstrated an optimal tensile strength for ENR latex to leach out all undesirable chemicals. The thickness of ENR-dipped film can be varied by selecting an appropriate concentration of latex TSC and coagulant, different dwelling times, and former temperatures. The determination of oil resistances showed that the oil uptake of ENRs in oils was substantially less than that of natural rubber (NR) and was comparable to commercial gloves. Aside from that, ENR demonstrated remarkable chemical resistance to acid and alkaline solutions.

Skim latex can be concentrated using an ultrafiltration process. It is a liquid separation process where water can be removed from latex through a membrane. Vulcanised dipped concentrated skim latex (CSK) films were prepared, and their properties were compared to commercial high ammonia natural rubber (HANR)-dipped films. As expected, HANR-dipped films were stronger as seen from the higher tensile and modulus values. However, the highest tensile strength and modulus values for CSK-dipped films stood at 17 MPa and 620%, respectively. Interestingly, the crosslink density of CSK-dipped films was higher than HANR-dipped films while the average molecular weight of rubber between crosslinks, M_c demonstrated the opposite. Both dipped films showed comparable results in oil and water uptakes, with CSK-dipped films having more water-resistance after prolonged immersion time than HANR-dipped films. The maximum decomposition temperature of CSK, i.e., 373.06 ^oC, and HANR dipped films, i.e., 374.08 ^oC, were almost identical. Interestingly, the TEM images revealed vulcanised CSK particles formed only intra-particle crosslinks, which agreed with the lower tensile strength, elongation at break (EB), crosslink density, and higher M_c. Overall, the non-rubber components and naturally occurring networks, with the influence of molecular weights, vulcanisation degree, and smaller particles, substantially affected the resulting CSK vulcanised dipped films.

The use of catalysts in rubber production industry has drastically altered production processes, increasing efficiency and quality. By solving polymer microstructure and elevating reactions, catalysts enable high-performance rubber improvement while minimising waste and energy consumption. Sustainable best practices, involving biodegradable rubber exploration and eco-friendly catalysts, contribute to long-term industry viability. In this mini literature review, we introduce various types of catalysts currently applied in the rubber industry and recent advancements in catalyst design for the future of rubber production. In the rubber industry, the selection of catalysts is a vital decision, which impact the efficiency of the polymerisation process and the quality of end products. Therefore, by carefully selecting catalysts with desired stereoselectivity and activity, producers can create synthetic rubbers with specific properties tailored to their real applications. By exploring the production of biodegradable rubber, this shift is vital for decreasing the environmental effect of rubber manufacturing and making the industries long-term environmentally friendly and sustainable.

Hevea brasiliensis, or the Para rubber tree, is a major commercial source of natural rubber (NR). The rubber tree is susceptible to various fungal attacks, which affect NR production and Corynespora cassiicola is one of the major pathogens affecting young and mature rubber trees. Corynespora leaf fall disease (CLFD) outbreaks often cause serious loss in latex productivity by adversely affecting tree health. Since fungicidal chemical control is uneconomical and unsustainable, improving host resistance is the most effective strategy for the long-term management of this disease. In this context, 78 Hevea genotypes were screened against two virulent isolates of two races of C. cassiicola (Race 1 and Race 2). The level of host resistance was determined in vitro using detached leaf bioassay and those genotypes that were found to be highly resistant were subjected to further evaluation under greenhouse conditions. Seven genotypes were classified as highly resistant against both races of C. cassicola in vitro, with less than 20% disease intensity. Subsequent assessment under greenhouse conditions identified three genotypes with less than 40% disease severity and corresponding rAUDPC value of less than 0.4 when challenged with both races of C. cassiicola. These resistant genotypes are suitable candidates to be included in breeding programmes aimed at the development of superior clones with durable resistance against Corynespora leaf fall disease.

A finite element model for analysing the sealing performance of three types of wellhead rotary blowout preventer rubber ring structures in use on site was established. By using this model, the stress, deformation and contact pressure distribution of the passive rubber ring during pre-tightening conditions were calculated when the inner annulus of the passive rubber ring passed through the 5-inch drill pipe body and the 7-inch joint. The distribution position, length, and magnitude of contact pressure on the contact surface between the three types of rubber rings and the outer wall of the drill string under different pressure penetration loads under rated working conditions were calculated. Overall, the sealing performance of the active rubber ring is the best while the sealing performance of the passive rubber ring is the worst. However, the passive rubber ring has a simple structure and does not require a hydraulic system, which makes it impossible to adjust the sealing strength of the rubber ring in real time based on the actual fluid pressure on site. On the other hand, the I-type rubber ring uses part of the rotating blowout preventer structure as the hydraulic chamber wall, which can thicken the rubber layer in contact with drill pipe. Therefore, passive rubber rings are more suitable for low fluid pressure drilling operations. When the fluid pressure at the lower part of the rubber ring exceeds the rated maximum fluid pressure, it will lead to a sharp decrease in the sealing performance of the rubber ring. Therefore, stricter control of the use of the rubber ring is needed during on-site use, especially in drilling conditions with wellhead fluid pressure. The research methods and achievements in the article provide theoretical guidance for the safety evaluation of rotary blowout preventers used in ultra deep wells unbalanced drilling.

Crumb rubber (CR) that had been used in an outdoor football stadium in the U.S.A. for over 10 years was sampled, analysed and compared to samples taken from an on-site, covered excess CR stockpile and from fresh CR that could be used to replace the used CR. These tests were accomplished to determine if the original CR properties had changed significantly, from new/un-used CR, which could have safety and performance implications if continued use of this CR was planned. A series of analytical and mechanical tests were performed to determine degradation effects over time that included Fourier-transform infrared spectroscopy (FTIR), solvent swell tests, differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), X-ray emission spectroscopy (XES), vertical impact, hardness and bulk density. Results inferred compositional differences and mechanical property changes between all three CR samples, with indications that the older CR was demonstrating concurrent increased crosslinking and molecular scissioning, with subsequent loss in resilience. The FTIR results indicated various polymer types present that originated from recycled automobile tyres as well as evidence of oxidation in the used CR. The DSC exhibited lower thermal enthalpy and higher glass transition temperatures confirming compositional changes in older samples. Both vertical impact and hardness tests showed a significant increase in hardness and lower resilience in the used CR. A significant decrease in average size in the used CR was revealed through sieving and microscopy, which indicated mechanical wear. Bulk density measurements of un-sieved used and stockpile CR showed a substantial increase in bulk density for the used samples. The fresh, new potential replacement CR appears to originate from a different supplier than the CR originally used on the sports surface (and accompanying stockpile CR) and possessed much higher resilience than the used CR.

This research aimed to design biocompatible polymeric surfactants as additives to natural rubber latex (NRL) and the mechanical properties of the latex films were evaluated thereafter. Both anionic and non-ionic surfactants, APS and NPS, were successfully synthesised from palm-based oleic acid by polyesterification, with their ester linkages verified by FTIR analysis. Both surfactants possess good thermal stability with thermal decomposition temperatures above 200 °C. They were biocompatible and non-cytotoxic, as evidenced by high cell viability > 80% for all tested cell lines. In general, the antibacterial activities of both surfactants were stronger against Gram-positive bacteria than Gram-negative bacteria. Surfactant solutions were prepared and compounded into NR latex to produce latex films. Both solutions exhibited good wetting properties with contact angles < 90°, low critical micelle concentration values ranging from 0.005 to 0.007 mol/L, low foaming ability, and reasonable foam stability above 80%. The unaged NR films compounded with APS demonstrated greater mechanical strengths than the control and NPS, recording the highest tensile strength of 28.65 MPa and the lowest modulus (M300) reflecting softness. Both latex films showed a slight reduction in mechanical properties after ageing. These results indicated that APS had a higher potential to modify NR latex film properties, in particular film softness. The surfactants also presented high potential as non-cytotoxic antimicrobial agents in NR compounding.