Journal of Rubber Research最新文献

Rubber (Hevea brasiliensis Müll. Arg.) is a major economic crop grown in tropical areas. However, the various service functions of rubber plantations and their benefit to society, the economy and the environment are still unclear. Data on rubber planting areas, dry rubber and wood yields, carbon sequestration and oxygen release capacities, biodiversity, employment, and market prices for natural rubber and rubber wood were collected. Observations of land use patterns and functions were carried out. The results showed that the capacity of average annual carbon stock capacity of rubber plantations in China was 36.51 million tonnes. The accumulation values of carbon sequestration and oxygen release, 416.89 million tonnes and 304.42 million tonnes, respectively. A total of 849 plant species, 60 bird species, 5 species of ground beetle, 25 species of wild bees, 27 ant species, 10 termite species, 87 spider species and 38 hemipterous species were found in rubber plantations. The average annual dry rubber and rubber wood yields were 676,300 tonnes and 1.29 million m³. From 2000 to 2020, 14.20 million tonnes of dry rubber were produced and 27.02 million m³ of wood were harvested. The average annual output of dry rubber and rubber wood was US$1.86 billion, while total output value summed to US$ 39.08 billion from 2000 to 2020. Rubber cultivation and plantation operation activities employed an average of 1.11 million people annually. Land use management and natural disasters may affect the service functions of rubber plantations, which are carbon sequestration and oxygen release, maintaining biodiversity, providing dry rubber and rubber wood, maintaining water and conserving water sources, absorbing employment, changing unsustainable agricultural practices and habits of smallholders and ethnic minorities, and promoting transfer of technologies. In the future, on the basis of recognising and rationally weighing the various functions of rubber plantations and their main driving factors, smallholders are expected to maximise the social, economic and ecological functions of rubber plantations through effective crop management and utilisation of resources.

Dialysed C-serum precipitate (DCP), a sub-fraction of latex C-serum originating from Hevea brasiliensis, has shown specific in vitro antiproliferative properties towards cancer-origin cell lines. As a potential agent to be used in cancer treatment, preclinical safety assessment tests are crucial. This study focused on investigating the mutagenicity of DCP via bacterial reverse mutation assay (Ames test), Mouse lymphoma assay (MLA), and micronucleus assay according to OECD guidelines. No mutagenicity was exhibited by DCP at concentrations lower than 1 mg/mL for the five different auxotroph strains of Salmonella typhimurium (TA 98, TA 100, TA 1535, and TA 1537) and Escherichia coli WP2uvrA pKM101 in the absence and presence of metabolic activation system (S9-mix). Nonetheless, it has been found that DCP was able to induce negligible mutation in MLA and micronucleus assay. Overall, DCP does express dose-dependant mutagenicity according to the assays conducted and thus, it is crucial to take this into consideration should DCP be used in the development of therapeutic agent.

Determining the partitioning of carbon black [CB] in miscible rubber–rubber blends [RRB’s] is a demanding problem in the rubber industry, testing one’s ability (especially tyre industry); hence, this research work aims to investigate the partitioning of CB in miscible styrene butadiene rubber [SBR]/butadiene rubber [BR] blends. SBR:BR with blend ratios of 70:30/50:50 and 30:70 with 50 phr CB were prepared on two-roll mill. Nanoscale partitioning of CB within the nanoscale phase-separated SBR/BR blends was quantitatively determined using dynamic mechanical analysis [DMA]. DMA confirmed 63%, 93%, and 45% of CB partitioning towards BR phases of 70:30, 50:50, and 30:70 in CB-filled SBR/BR blends. An attempt to determine the partitioning of CB was also made by making use of solid-state nuclear magnetic resonance spectroscopy [SS-NMR spectroscopy] to interrelate the partitioning of CB determined using DMA. TEM images were helpful in observing CB's dispersion and network ability in CB-filled SBR/BR blends. The results of CB partitioning confirm maximum partitioning of CB towards the nano-dispersed phase in CB-filled SBR/BR blends and are in well agreement with the constrained regions of BR and mechanical properties of CB-filled SBR/BR blends. Attenuated total reflectance-Fourier transform infrared spectroscopy’s (ATR-FTIR spectroscopy) spectra were used as a tool to determine the interactions within CB-filled rubbers and RRB’s in comparison to their neat counterparts. To the best of our knowledge, partitioning of CB controlled by nanoscale phase-separated morphology and its effect on mechanical properties has not been studied so far; hence, this study would be significant to academics and industrial researchers working in the area of rubber composites.

To improve the biocompatibility of dipped films from natural rubber latex (NRL) without compromising physical strength, high ammoniated NRL (HA-NRL) compounding formulations were devised by manipulating the amount of compounding ingredients and additive materials. In this study, the compatibility of 3-aminoproplymethyldiethoxysilane (APMDS) with calcium carbonate (CaCO₃) filler in zinc diethyldithiocarbamate (ZDEC) accelerated HA-NRL formulas were explored. It was found that ZDEC residue detected using High-Performance Liquid Chromatography (HPLC) was less than 6 μ/g in all NRL-dipped films. Furthermore, the cytotoxicity response of the films showed a lower toxicity effect in the presence of APMDS. The occurrence of chemical interactions between APMDS, CaCO₃ and crosslinked NR was confirmed by the Attenuated Total Reflectance-Fourier Transmittance Infra-Red (ATR-FTIR) spectrometer. Interestingly, the physical strength of NRL-dipped film was greatly improved when APMDS was incorporated together with CaCO₃ at a low dosage of ZDEC. This may be due to the adequate physical interaction between the APMDS-surface-modified filler particles and APMDS-surface-modified rubber particles. Overall, a biocompatible NRL film with satisfactory physical strength, low ZDEC residue and low cytotoxicity was achieved by employing a low dosage of ZDEC in the presence of APMDS and CaCO₃.

Purified natural rubber was successfully prepared in the presence of a denaturant named guanidine hydrochloride (GNH). In this work, fresh field natural rubber (FNR) latex was used as a starting material. The conditions of purification such as the effect of GNH concentrations, incubation time and temperature were studied. The results showed that the soluble protein-free natural rubber (SPFNR) contained undetectable extractable (EP) and antigenic (AP) protein, and very low nitrogen content, i.e. 0.013 wt% at GNH concentration of 0.1 phr, after 1-h incubation at 30 °C. These results were supported by the Fourier transform infrared (FTIR) spectroscopy, where the absorption peak of the amine functional group (proteins) disappeared substantially and the fatty acid ester functional group (lipids) decreased swiftly after purification. Transmission electron microscope (TEM) images showed that the non-rubber component matrix disappeared in the SPFNR film. Less water hydration was obtained for the SPFNR film, which was reflected by a lower water uptake percentage than the FNR film. Furthermore, the thermal property determined by a thermogravimetric analyzer (TGA) showed that FNR and SPFNR films were comparable to each other. The stress at break showed that the FNR film was superior to the SPFNR film. Interestingly, the strain at break was about similar for both films, indicating the SPFNR film has softer and more elastic characteristics.

Accumulation of heavy metals in plant parts due to environmental uptake may have repercussions on the plant's health and integrity. In this study, we quantified various heavy metals in natural rubber (NR) latex collected from Mantin, Negeri Sembilan, Malaysia (sub-urban area) and Batu Embun, Pahang, Malaysia (rural area) for 12 consecutive months. Acid digestion as sample pre-treatment was performed prior to detection and quantification of the heavy metals, namely Cr, Cu, Fe, Mn, Pb, and Zn, using inductively coupled plasma–optical emission spectrometer (ICP-OES). Then, plasticity test and preparation of polystyrene/natural rubber (PS/NR) blends were conducted to investigate the effects of heavy metals on the integrity of NR. It was found that the plasticity retention index (PRI) was inversely proportional to the concentration of heavy metals in NR. Conversely, high levels of heavy metals in latex had acted as an excellent compatibilizer in PS/NR blends with improved properties of tensile strength and impact energy. The most deposited heavy metals (4391.2 ppm) compatibilized PS/NR blends with the highest tensile strength of 27.4 MPa and impact energy of 17.55 kJ/m². In contrast, the least accumulated heavy metals (18.8 ppm) resulted in PS/NR blends with the lowest tensile strength (2.61 MPa) and impact energy (2.70 kJ/m²). The phase distribution of PS/NR was observed to be more uniformed when high levels of heavy metals were available in the blends. Our discovery has indirectly demonstrated the role of NR in eliminating heavy metals from the environment which in turn, acting as a good compatibilizer in the blending of PS/NR.

Waste-rubberized ceramsite concrete is an improvised building material that is suitable for lightweight wall panels, which can significantly reduce the bulk density of buildings. In this study, the effects of different water–cement ratios on the mechanical properties, water absorption, ultrasonic velocity, and sulfate corrosion resistance of waste-rubberized ceramsite concrete were investigated, and scanning electron microscopy (SEM) was used to study the microscopic interface. The test results show that the water–cement ratio of 0.45 is optimal. The compressive strength, water absorption rate, and ultrasonic velocity of the specimen first increased and then decreased as the water–cement ratio increased. The sulfate corrosion resistance of specimens with a high water–cement ratio is weaker than that of specimens with a low water–cement ratio. It is of great significance to explore the optimal water–cement ratio of the waste-rubberized ceramsite concrete for further research, and it has important production guidance significance for commercial applications.

In this study, recovered silica fillers from pyrolysis and geothermal sources, referred to as ‘rSilica’ and ‘geoSilica’, respectively, have been mixed with epoxidised natural rubber (ENR) to determine whether they can be used to improve the sustainability of ‘green’ tyre tread compounds. The effect of using silica recovered by a geothermal and pyrolysis process as filler in an ENR compound with and without X50S silane coupling agent was investigated in this study. Both recovered silicas also have been characterised and the physical and mechanical properties of the filled ENR compounds measured. All the results obtained have been compared with the industrial silica grade of Zeosil 1165. Based on the test results obtained, rSilica did show reasonably good physical properties such as tensile strength, hardness and abrasion resistance as well as good processing characteristics compared to the commercial-grade silica (Zeosil). rSilica-filled ENR compounds with silane also showed better physical properties than the non-silane compound, which indicates that rSilica still can react with the silane, despite the fact that the amount of silanol groups on the rSilica surface were reduced by the pyrolysis process.

In this study, a novel polymeric blend was developed using recycled high-density polyethylene (rHDPE) and natural rubber (NR), along with kenaf fibre as a natural filler. In addition, the blends were compatibilised by maleic anhydride-grafted polyethylene (MAPE) and maleic anhydride-grafted natural rubber (MANR). In addition, this study focussed on the material’s properties after the natural weathering test. Results indicated that the tensile properties dropped over the period of natural weathering due to the chain scission of polymeric backbones and the degradation of kenaf fibre. It was found that the retention of properties after natural weathering was higher over the addition of kenaf fibre. When considering the tensile strength, adding only 10 phr of kenaf enabled to increase the retention up to 25% higher than the unfilled counterpart. However, the retained properties were limited for the blends with the addition of compatibilisers. Adding compatibilisers might speed up the degradation of the blends due to its tendency to promote degradation. This is very useful for plastic manufacturers to consider this material a choice either to act as a performance booster or a pro-degradant.