Journal of Rubber Research最新文献

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.

Specialty natural rubber (SpNR) latex foam is a natural-based acoustic foam material, that can substitute conventional synthetic foams to control noise pollution in buildings and in the transportation industry. However, the thermal stability of SpNR latex foam must be improved to meet the required safety criteria for buildings. The goal of the study is to investigate the feasibility of oil palm trunk biochar (OPTB) as a flame-retardant ingredient in two types of SpNR latex foam: deproteinized natural rubber latex foam and epoxidized natural rubber latex foam. The effects of different levels of OPTB loading (8 phr, 16 phr, and 24 phr) on the thermal stability and acoustic properties of OPTB/SpNR latex foam composites were examined. Thermogravimetric analysis indicates that the OPTB has excellent flame-retardant characteristics. The addition of OPTB to SpNR latex foam decreased the thermal decomposition rate of SpNR latex foam but was still insufficient to meet the building fire rating requirements. This study also found that the addition of OPTB to SpNR latex foam increased sound transmission loss but decreased the sound absorption coefficient values. Owing to the fact that OPTB is cheaper than SpNR latex, the addition of OPTB to SpNR latex foam could lead to cost savings in the production of the acoustic foam material. Additionally, this study contributes to sustainable material development by converting OPTB, a by-product from oil palm plantations into value-added products, which is in line with global environmental aspirations.

For the outdoor insulation of high voltage transmission lines, insulating materials made of high-temperature vulcanized silicone rubber (HTV-SiR) are used all over the world. To enhance the performance of these base polymers, fillers of various sizes, concentrations and dimensions are added. In this study, four different types of HTV-SiR materials, one unfilled and three reinforced with silica of micro/nano size were used. Followed by preparation of the samples, aging was performed by placing them in a specially designed weathering chamber with various stresses and bipolar DC voltage for 5000 h. To diagnose integrity of the aged materials, different types of measurements based on hydrophobicity classification, leakage current, mechanical analysis, thermal tests, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were conducted. Results of the hydrophobicity classification revealed S₃ to be most hydrophobic having HC2 class under the influence of bipolar DC voltage, whereas, sample S₁ was the most hydrophilic resulting in HC4 and HC5 under negative and positive DC voltages, respectively. Similarly, the lowest leakage currents of 5.56 μA and 5.81 μA were recorded for sample S₃ after being aged under negative DC and positive DC voltages, respectively. The %age decrease in tensile strength recorded for samples S₁, S₂, S₃ and S₄ was 32.3, 25.32, 23.56 and 27.12, respectively, under the positive DC voltage. Thermogravimetric analysis exhibited the least decrease of %yield from 49.3% to 48.9% and 48.4% for sample S₃ under negative and positive DC voltages, respectively. Additionally, according to FTIR spectroscopic investigation, hybrid composite S₃ kept the highest intactness in siloxane backbone (Si–O–Si) linkages, with a drop in its peak of 37% for positive DC and 11.2% for negative DC. In contrast to the co-filled composites S₂ and S₃ with improved surface morphology, samples S₁ and S₄ indicated voids, cracks, increased roughness and structural damages.

To run a smallholder rubber plantation as a productive and profitable venture, the higher motivation of its waged labourers to their operational role in farming is essential. This study adopted Maslow’s hierarchy of needs theory to identify the existing satisfactory level of smallholder rubber plantation labourers in latex harvesting in Sri Lanka. It formulates the relevant probabilities of improving job satisfaction concerning their satisfaction with needs. Using the ordered logistic regression, we examined the socio-demographic and job-specific environmental characteristics of 231 latex harvesters from the smallholder rubber lands in the Kegalle District of Sri Lanka. Our results revealed that the overall satisfaction of a latex harvester lies between dissatisfaction to a neutral level. Moreover, it can be improved by 5%–11% when the satisfaction level goes from dissatisfied to satisfied level in hierarchical needs. Results of the field survey suggest that working environment improvement of latex harvesters, relationships with the owner and incentives to harvesters are the foremost needs to motivate harvesters in the job. Some measures were discussed to uplift the satisfactory level of harvesters while safeguarding the smallholder rubber growers. Further investigation into other regions with diverse socioeconomic characteristics was also discussed to generalise the findings of this study.

Blending is an economical and feasible method to improve the properties of polymers. To improve the mechanical properties of ethylene acrylate rubber (AEM), a series of hydrogenated nitrile butadiene rubber (HNBR)/AEM blends were prepared. The mechanical, thermal properties and compatibility of HNBR/AEM blends were investigated in detail. Carbon black filled HNBR/AEM blends exhibited excellent mechanical properties as well as good resistance to high and low temperature. The reactivity of HNBR was higher than that of AEM at a high temperature (180 °C) in air. The crosslinking reaction was more likely to occur in HNBR rubber, while it is not easy to remove small molecules at high temperature. The degradation temperature (T_d5%) of AEM (350 °C) was lower than that of HNBR (390 °C), while the hot-air ageing tests indicate that the retention of tensile strength of AEM (95%) was much higher than that of HNBR (58%). HNBR/AEM blends were compatible within the full range of formulations, and have been mutually validated by SEM, dynamic mechanical analysis and mechanical property models of HNBR/AEM blends.

Concentrated skim (CSk) latex was prepared from raw skim (RSk) latex of Hevea brasilliensis via membrane separation process. Since the properties of CSk latex have not been reported previously, this work aims to study the properties of CSk latex and juxtapose it with raw skim (RSk), field (FNR) and high ammonia (HANR) latexes. The physicochemical properties of the latexes, such as total solid content (TSC), zeta potential, and pH, were analogous to FNR latex. CSK and RSk latexes were composed of small rubber particles as confirmed by SEM, with low molecular weight polymer as determined by gel permeation chromatography (GPC). The Fourier infra-red transform (FTIR) spectroscopy confirmed that CSk film contained high fatty acid ester, nitrogen and gel contents. After the ultra-filtration (UF) membrane separation, TSC increased from 7.3 wt% to 39.6 wt%. The non-rubber components and metal ion content were markedly decreased by 50%, respectively. About 85% of fatty acid esters were removed by acetone extraction (AE) while nitrogen and gel content remained the same in CSk film. This could be attributed to proteins forming cross-links that lead to high gel content of skim latex. In addition, CSk film showed marked improvement in thermal stability as compared to that of RSk.