Journal of Rubber Research最新文献

The global demand for natural rubber emphasizes the need for increasing yield per hectare as the expansion of planting areas becomes difficult. To overcome some of the limitations related to the propagation of rubber trees through grafting, research has been carried out for years on Hevea clonal plants produced by in vitro tissue culture technology (vitroplants, VP). This study conducts a large-scale evaluation of VP across two rubber estates in Ivory Coast and Ghana. Using VP could significantly reduce the growth time of seedlings in the nursery and provide flexibility in planting schedules independent of seed availability. For 66 months, 14 ha of field trials were monitored to compare growth dynamics, stand uniformity, and trunk conicity of VP with trees from grafted plants (GP) of RRIM600 clone. The findings reveal that VP exhibited superior trunk girth at 66 months, suggesting an earlier readiness for tapping compared to GP with a more conical trunk shape, which may lead to increased latex yield. The differences in growth rates in the field between VP and GP were significantly affected by the developmental stage of the plants at planting, with VP being planted with fully developed leaves and self-rooted systems, while GP were planted with developed rootstocks but dormant buds. This enabled VP to establish more rapidly and thus reach readiness for latex tapping sooner than GP. The study underscores the importance of further research on clonal selection, acclimatization period, rootstock interactions and the yield performances of this novel planting material.

Latex allergies are caused by latex protein and the chemicals such as accelerators added during the manufacturing of its products. Cytotoxicity and hypersensitivity type I and type IV reactions are the common clinical manifestations of natural rubber latex (NRL). The study is to evaluate the cytotoxic effect of medical gloves prepared by diisopropyl xanthogen polysulfide (DIXP) and zinc diisononyl dithiocarbamate (ZDNC), which are claimed to be safer than conventional accelerators towards HaCat cells. Gloves prepared with varying concentrations of DIXP and ZDNC were subjected to cytotoxic tests, specifically agar overlay assay, filter diffusion test and MTT test, which HaCat Cell lines were used as the in vitro model. The tests showed that all the gloves prepared with DIXP (1.0, 1.2 and 1.5 phr) shows mild cytotoxicity while the gloves prepared with 1.0 phr of ZDNC has no cytotoxic effect in the agar overlay and filter diffusion tests. However, gloves prepared with 1.2 and 1.5 phr of ZDNC showed mild cytotoxicity in both tests. As for the MTT test, both DIXP and ZDNC gloves regardless of the concentration, showed a steady cell viability above 80% before decreasing to less than 20% at higher concentrations of 50% and 100% of sample concentration prepared by two-fold serial dilution. Taken together, the results suggest that ZDNC is a more viable and safer alternative for replacing conventional accelerators. Further testing is necessary to confirm the cytotoxicity of ZDNC particularly at a concentration not exceeding 1.0 phr.

This work is the first attempt to establish a practical quantification protocol for novel palm-based polymeric surfactants AS1, AS2, and AS3. The method is optimised for natural rubber latex (NRL), not aqueous media. Conductivity is proposed as a novel application for field detection, not as a new analytical principle. Other analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), zeta potential analysis, thermogravimetric analysis (TGA), conductivity measurement, and contact angle measurements were also explored as the qualitative and quantification methods for novel palm-based polymeric surfactants in NRL. Among these methods, conductivity measurement shows the greatest promise for both qualitative and quantitative determination of AS1, AS2, and AS3 in latex. These surfactants exhibit characteristic anionic electrical conductivity, with a strong linear relationship observed between conductivity and surfactant concentration (R² >0.99). Contact angle measurements provided insights into the surfactant characteristics, including hydrophilic properties and surface absorption behaviour; however, they may not be suitable for quantification, as the data show a polynomial relationship with a poor fit (R² < 0.99). Zeta potential analysis indicated consistent colloidal stability across all samples, which displayed consistent − 30 to -50 mV. FTIR analysis offered valuable qualitative insights, particularly for functional group identification, while TGA analysis assessed thermal stability and degradation. Although FTIR, zeta potential, and TGA analyses are effective for characterising the impact of the surfactants on latex properties, they may not be suitable for quantification purposes. All methods exhibited some detection limitations, highlighting the need for further refinement and exploration to enhance their reliability and accuracy.

Income derived from rubber cultivation constitutes a crucial source of price for rubber growers in tropical China. However, the persistently low market prices for rubber since 2014 have rendered the livelihoods of these growers precarious, significantly increasing their risk of relative poverty. Price insurance, serving as a financial instrument to underwrite the incomes of rubber growers, plays a vital role in stabilising their earnings and alleviating relative poverty. This paper utilises micro-survey data from 441 rubber growers in Hainan Province, a primary rubber-producing region in China, collected in December 2021, to examine the mechanisms and heterogeneous effects of price insurance purchases on the relative poverty of these growers. The findings indicate that the purchase of price insurance by rubber growers can substantially reduce their relative poverty levels. Furthermore, according to a counterfactual analysis, the relative poverty of rubber growers who purchased price insurance would have increased by 18.5% had they not purchased price insurance, and the relative poverty of those who do not purchase price insurance would have decreased by 25.3% had they purchased price insurance. The alleviation of relative poverty through price insurance occurs via mechanisms such as enhancing capital input enthusiasm and labour input enthusiasm among rubber growers. Additionally, the impact of price insurance on poverty alleviation is notably more pronounced among “rubber plantation income-based growers” and “new generation rubber growers”. The findings of this study offer significant practical implications for policymakers seeking to implement price insurance-based poverty reduction initiatives in Hainan and other natural rubber-producing regions across China.

Clinical trial number

Not applicable.

Methyl vinyl silicone rubber (MVQ) suffers from intrinsic mechanical weakness and environmental aging. To address these issues, we developed grafted-opal@CeOx (g-opal@CeOx) via thiol-ene click chemistry, integrating interfacial compatibility enhancement with CeOx-based anti-aging functionality. The Kissinger method was used to calculate the average apparent activation energy of crosslinking reactions. The Mooney viscosity values, viscoelasticity analysis and molecular dynamics simulation results demonstrated that g-opal@CeOx enhanced the interfacial compatibility between MVQ and opal. After adding 12 g of g-opal@CeOx, the tear strength increased by 3.1 times compared to MVQ and the tensile strength was 2.16 times that of MVQ. Molecular dynamics simulations quantitatively confirmed strengthened interfacial interactions between MVQ and g-opal@CeOx. The UV aging test showed that MVQ was mainly crosslinked in the early stage of aging, and mainly hydrolyzed and broken in the later stage. Adding g-opal@CeOx to MVQ reduced the percentage of tensile strength loss from 23.5% to 10.4% and only reduced the contact angle by 7°. The thermal-oxidative aging kinetic analysis showed that g-opal@CeOx extended the lifespan of MVQ in thermal oxidation environments.

Forest plantation is an alternative to forest restoration program to supply high quality timber materials and adopt a sustainable management system. A suitable forest species can be used to occupy the overused and degraded soils. Rubber clones as forest plantation species could offer many advantages such as short planting cycle of 15 years, suitability for Malaysia tropical climate, dual income from latex and wood production, and good quality wood. In this study, seventeen rubber clones were planted in the Rubber Forest Clone Trials in two locations: Chikus Forest Reserve in Perak and RRIMINIS Lakai in Negeri Sembilan. The best performing clones in Lakai and Chikus are RRIM 2024 and RRIM 3001, respectively. Using the data from five common clones, girth and clear bole volume were found to be higher in Lakai than Chikus. RRIM 2024 can reach tappable girth of 45 cm after five years of planting in Lakai and it recorded the highest clear bole volume of 0.3 m³ at 13 years after planting. The study found significant positive correlations of girth and bole volume increments with relative humidity and temperature, while significant negative correlations with soil class, windspeed and solar radiation. No significant correlation can be observed for rainfall volume due to the similar rainfall record for both locations. RRIM 2024 and RRIM 3001 proven to have vigorous growth and wood volume and thus are recommended for planting in the Rubber Forest Plantation program.

The triploid rubber tree cultivar Yunyan 77−4 is widely planted for quick growth and resistance to cold in Yunnan, China. However, during the regular tapping rubber period from April to November or December, the heat can cause latex flow obstruction, significantly reducing the tree’s yield. Tapping rubber during the winter and dry season may become a feasible option because low temperatures encourage latex flow. This study used Yunyan 77−4 natural rubber trees stimulated by irrigation and ethephon stimulation to examine changes in the qualities of natural rubber (NR) during the winter and dry season. According to the experimental results, the dry rubber content, total solid content, Mooney viscosity, and P₀ all showed a trend of decreasing and then increasing under the influence of temperature and humidity. The lowest values occurred in the control group at the lowest temperatures in December or January of the following year at 30.56%, 35.39%, 54, and 30, respectively. These values could be suitably increased by irrigation and chemical stimulation treatments. Ash, nitrogen content, and mechanical characteristics tended to rise and then fall, with maximum values of 0.49%, 0.62%, and 20.16 MPa, respectively, and the two treatments had little effect on them. The molecular weight appeared to peak during the first month of tapping rubber, the volatile component decreased as a whole, and the dirt content fluctuated little during the entire trial. The experiment also found that the two treatments would reduce the antioxidant properties of NR. The results of this study provided information about the properties of the NR of Yunyan 77−4, which served as a theoretical foundation for the popularization, application, and performance regulation of tapping rubber in the winter and dry season.

Carbon nanotubes (CNTs) were incorporated to create nanocomposites of ethylene-propylene-diene monomer (EPDM) and styrene-butadiene rubber (SBR). These nanocomposites underwent comprehensive evaluation of their cure and mechanical properties, specifically assessing tensile strength, elongation at break, tear strength, stress at 100% elongation, rebound resilience, and hardness. Additional assessments included abrasion resistance, swelling resistance, crosslinking density, compression set, and morphology. Results from mechanical testing demonstrated substantial improvements in key properties, with tensile strength increased by up to 99% and stress at 100% elongation enhanced by up to 29%, relative to pure EPDM/SBR blends. To gain deeper insights into the nanocomposite structure, the dispersion state of CNTs within the EPDM/SBR matrix was investigated using Field Emission Scanning Electron Microscopy (FESEM), revealing the morphology and distribution of CNTs throughout the rubber matrix.

This study investigates the thermo–mechanical behavior of rotating disks made from natural rubber (NR) and polystyrene (PS) under edge-loading conditions, focusing on the effects of radius ratio, axial load, and temperature on yield initiation and stress distribution. The critical angular speed for yield initiation decreases with increasing radius ratio and axial load for both materials, with NR exhibiting greater sensitivity due to its viscoelastic nature and thermal softening at elevated temperatures. PS demonstrates higher mechanical stability and resistance to deformation under similar conditions. Stress analysis shows that hoop stress decreases significantly in NR as temperature rises, especially under combined axial load, indicating a higher risk of early yielding. Radial stress varies with load and temperature but remains lower than hoop stress, emphasizing the dominant role of circumferential stress in material failure. These findings provide valuable guidance for the design and material selection of rotating components in automotive and industrial applications, ensuring improved performance and durability under complex thermal and mechanical loading.

This study examines the influence of accelerated weathering on the mechanical properties of grafted binary blend (Room Temperature Vulcanized Silicone Rubber (RTV-SIR)/polyurethane Rubber (PUR) intended for prosthetic feet. Employing an accelerated weathering environment replicating natural conditions, encompassing UV radiation, condensation, and water spray, the samples produced by the vacuum desiccator were exposed for a duration of 100 h. Grafted binary blend samples of (PUR) with (10, 20, and 30 wt.% RTV-SIR) blended to achieve different properties to use for prosthetic foot, using 0.1% of Tetraethoxysilane (TEOS) as a coupling agent to enhance compatibility between components. To compare, mechanical tests characterised tensile, tear, compression, and hardness properties of weathered and unweather samples. Fourier-transform infrared spectroscopy (FTIR) also analysed the efficiency of the TEOS treatment of binary rubber blend samples. Field emission-scanning electron microscopy (FE-SEM) was employed to investigate the morphology and interfacial adhesion between the components. The findings illustrate increased mechanical properties with weathering exposure, and FESEM showed better interfacial adhesion between blend components for (10–20 wt. % RTV-SIR). This work proves that the binary rubber blend was more resistant to accelerated weathering than its components and is compatible with a weight ratio of less than 30% of RTV-SIR.

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