Journal of Rubber Research最新文献

Rubber plantations are an important component of tropical forest ecosystems and are emerging as crucial contributors to carbon sequestration in the tropics. However, ecosystem respiration (RECO), which constitutes an essential constraint on the carbon fixation capacity of rubber plantations, and its driving mechanisms remains unclear. Therefore, this study developed a data-driven semi-empirical model to simulate rubber plantations RECO utilising eddy covariance flux measurements and was upscaled to Hainan Island using remote sensing images and climatic data. Numerical simulations experiments analysed direct and indirect of climatic factors impacts on rubber plantations RECO. The results showed that the model accurately captured RECO trends and seasonality (R² = 0.87, RMSE = 1.27 g C m⁻² d⁻¹); in the past 19 years, RECO showed a noticeable increase, particularly in the late rainy season and the seasonality of RECO has shown a delayed pattern. The RECO in the central region (52% area) exhibited multimodal enhancement while northern and southern regions (37% area) showed oscillations or decreases. Temporally, RECO is higher in the rainy season compared to the dry season, and spatially, RECO is higher in the southern region than in the northern region. Among the climatic factors, water conditions (rainfall and air humidity) have been emerged as dominant factors (5.38%) influencing RECO, surpassing temperature (3.96%) and radiation (3.81%). In addition, climatic factors make a positive overall contribution during the dry season but perform oppositely in the rainy season. This study offers theoretical and technical insights into high carbon sink management in rubber plantations and carbon sequestration in tropical forests ecosystems.

In the current study, samples were taken from the sewage treatment plant to isolate rubber-degrading microbial strains. The sludge samples were screened for rubber degradation microbes and later on, each strain was separately characterised for rubber degradation. Initially, strain BA23 showed half the rubber degradation ratio in mineral salt medium. The isolated microbial strains were identified based on 16SrRNA gene sequence analysis, morphological and biochemical characteristics and named Brucella sp. belonging to the genus Bacillus. Later on, the medium conditions for strain BA23 were optimised based on carbon, nitrogen sources, pH, temperature and incubation period. After optimising various environmental and nutritional conditions, the rubber degradation increased twice when inorganic nitrogen sources (aammonium nitrate) used 1 g/L in the medium at pH 7.5. Furthermore, the structural changes that occurred in the rubber polymer associated with the rubber polymer were analysed through Fourier transform infrared spectroscopy (FTIR) and the breakdown of important functional groups such as aldehyde, ketone ester and carboxylic acid was observed. Finally, the gravimetric weight loss of CO₂ during rubber degradation was 42.88 g/L, showing CO₂ evolution greatly when the rubber degradation occurred in the mineral salt medium. It was concluded that strain BA23 has a maximum potential for rubber degradation when it is used for future solid waste management of rubber and its products for a long period in the environment.

The article focuses on synthesising a new nanocomposite incorporating ZnS filler and investigating its structure, optical properties and specific electrical conductivity. In this study, expanded perlite (EP) and butadiene rubber (BR) underwent simultaneous oxidative chlorophosphorylation and subsequent hydrolysis. ZnS nanoparticles were then grown on the crosslinked/ion-exchange composite (EP-PhBR) using the Successive Ionic Layer Adsorption and Reaction (SILAR) method, resulting in the ZnS/EP-PhBR nanocomposite. The structure of the nanocomposite was characterised through UV-Vis spectroscopy and X-ray diffraction analysis. Embedding ZnS nanoparticles in EP-PhBR caused a reduction in the optical band gap from 3.18 eV to 3.045 eV, signifying increased disorder in ZnS nanoparticles due to alterations in the nanocomposite’s intermolecular structure. XRD studies revealed cubic crystal-structured ZnS nanoparticles with an average size of approximately 3 nm in the ZnS/EP-PhBR nanocomposite. The specific electrical conductivity (σ) at ambient temperature demonstrated the enhanced crystallinity of EP-PhBR, attributed to interfacial interactions with ZnS nanoparticles and the developed nanolayers. The ZnS/EP-PhBR nanocomposite exhibited favourable properties, making it a promising material for photocatalysis and solar cell applications.

Pestalotiopsis leaf fall disease (PLFD) has emerged as a significant and detrimental foliar disease affecting Hevea brasiliensis in Malaysia since 2017. The disease poses a severe threat to rubber plantations, leading to economic losses and impacting the country’s rubber industry. Understanding the factors contributing to lesion incidence and the potential presence of a fungal complex is crucial for effective disease management. This study aimed to address key objectives, including the identification of primary fungal pathogens responsible for lesion development and examination of the role of co-infections in lesion incidence. To achieve these objectives, five fungal isolates (Neopestalotiopsis surinamensis, Colletotrichum conoides, Lasiodiplodia theobromae, Phyllosticta fallopiae and Letendraea cordylinicola) previously identified through the Internal Transcribe Spacer (ITS) regions were subjected to in vitro artificial inoculation experiments on detached rubber leaves. Various combinations of these fungal isolates were tested to evaluate their interactions as possible causal pathogens of PLFD. Three variables were assessed, viz. type of water source (sterile distilled water and rainwater), presence of leaf wounds, and inoculation techniques (conidial suspensions and mycelial agar plugs). Lesion incidence was evaluated based on sporulating occurrences on the detached leaves, recorded seven days after inoculation. Statistical analysis, including non-parametric Pearson’s chi-square tests revealed that the fungal isolates Lasiodiplodia theobromae, Colletotrichum conoides and Neopestalotiopsis surinamensis were the primary contributors to lesion incidence, accounting for 83%, 69%, and 57% of cases, respectively. The study also revealed that lesion incidence was not significantly influenced by inoculation techniques or type of water source but was greater in wounded leaves compared to unwounded leaves. Co-inoculation experiments demonstrated increased lesion incidence, highlighting the role of co-infections in disease severity. Importantly, this study elucidated a potential fungal complex associated with PLFD and provided insights into its epidemiology. The findings contribute to deeper understanding of the disease, offering valuable guidance for effective disease management strategies in H. brasiliensis cultivation in Malaysia.

The focus of this study is on the evaluation of the effect of different types of inorganic fillers on the different major properties of natural rubber latex (NRL) foam vulcanisates. The mechanical and chemical properties of filled NRL foam were evaluated and compared with unfilled vulcanisate as per BIS standards IS 1741:2019 and IS: 6664 (1992) RA 2004 specification. The different fillers at various loadings selected for this study were marble powder, talc and China clay. From this study, talc was found to impart good mechanical properties such as indentation hardness index, flexing properties, compression set at constant strain and stress and split tear strength. It was also found that the chemical properties such as ageing resistance and water absorption properties for talc-filled foam were found to be equivalent to NRL foam without filler. Amongst the fillers studied talc possesses better mechanical and chemical properties followed by marble powder and China clay. Scanning electron microscope (SEM) image analysis of NRL foam at 500 μm scale with talc is self-explanatory to the above-mentioned facts.

Flexible antennas are placed near or on the human body without having an adverse effect on it. Therefore, they must be comfortable, flexible and not contribute to discomfort. At the same time, they must have a small value of the tangent of the angle of dielectric loss (tan δ_ε), a minimum absorption of electromagnetic power, the ability to withstand mechanical loads and have a small change in the complex dielectric permittivity in a wide frequency range. The aim of the study is to verify the possibilities of using spinel pigments as fillers in styrene-butadiene rubber composites applicable as substrates and insulating layers in flexible portable antennas for wireless communications. It was found that the filler used has characteristics that ensure good performance of the antenna, combined with an aesthetic appearance. The optimal concentration of the spinel pigment, which determines the best operational characteristics of the antenna, has been established.

Ethylene plays a role of gas hormone generated in response to varied stress in plant cells. In Hevea brasiliensis, periodic ethephon stimulation of tapped trees generates a dilution of the latex, a lower Total Solid Content (TSC) and a lower viscosity, resulting in a longer duration of the latex flow and a higher production of the following tappings. It also increases latex regeneration between two subsequent tappings. These mechanisms induce important changes in the laticifer metabolism and in the cellular genetic expression. Ethephon stimulation has become a major tool for tapping management. However, its excessive use can increase the susceptibility of trees to tapping panel dryness (TPD). A newly formulated ethephon water-based stimulant (RRIM HYDROBEST^TM, or RHB) is studied. A field trial was set with the clone RRIM 3001, comparing 4 stimulant treatments: ns = non-stimulated = control, ET = Ethephon 5%, MTX = MORTEX 5%, and RHB = RRIM HYDROBEST™ 5%. The production per tree was higher for MTX than for ns and ET, with RHB intermediate between both groups. The dry cut length (DCL) percentage of RHB was lower than that of ns, ET and MTX. Concerning the sucrose content of the latex measured in high-yielding and low-yielding periods, for the control ns alone, sucrose content in the low-yielding period was higher than that in the high-yielding period. Concerning the RHB treatment, in comparison with the control, 75 differentially expressed transcription factors were found, with most of them members of the ERF family. These results are discussed.

In this work, the mechanical behaviour of a thick-walled cylindrical pressure vessel composed of an incompressible isotropic non-linearly hyper-elastic material subjected to internal and/or external pressure is investigated. An analytical solution is proposed for the general form of the free strain energy density and different models including Neo–Hookean, Mooney–Rivlin, and Yeoh are employed. An analysis was conducted to determine the extension ratio at the inner and outer radii as well as the stress distribution, in different cases, namely the application of internal pressure only, external pressure only, and internal and external pressure applied simultaneously. In addition, various pressure values are applied to account for different levels of deformation. In order to strengthen the analytical solution, a finite element model of the pressurised vessel was constructed. A very good agreement has been found between the analytical predictions and the numerical results, suggesting the accuracy of the analytical solution. The analytical solution can be used for parametric studies (material or geometrical parameters) and the design/optimisation of a thick-walled cylindrical pressure vessel subjected to internal and/or external pressure. Additionally, it obviates the requirement for many finite element simulations, where computational cost is an important parameter.

Additive manufacturing, also known as 3D printing, is transforming the industry and becoming more common every day due to its considerable time saving and lower costs, compared to the established conventional manufacturing methods. The mechanical strength of 3D printed products is affected by the parameters of the 3D printing process. Thermoplastic Polyurethane (TPU) is a type of elastomer, capable of being used on any fused deposition modelling (FDM) 3D printer. A series of TPU test pieces with different infill density and patterns were produced using a FDM printer. The influence of infill parameters on the 3D part’s mechanical properties has been evaluated. Five patterns with a range of infill densities were compared in this study. The tensile properties of the printed specimens were influenced by the infill density, whereas the infill pattern used in this study has marginal effects. The grid pattern with 100% infill density showed the highest tensile strength, with a value of 4.43 MPa. The results were compared with specimens, which were prepared through conventional compression moulding. The dynamic mechanical thermal analysis (DMTA) and load–deflection analysis (LDA) tests showed that specimens with 100% infill density may not be significantly affected by different infill patterns selected in this study under low strain testing conditions.