Journal of Rubber Research最新文献

A large number of waste tires are discarded every year. These waste tires will have a great impact on the environment. If they can be recycled, environmental and economic benefits can be obtained. In this paper, rubber powder is added to concrete, and a variety of analytical methods are used to study the effect of rubber powder on the performance of concrete. Experiments show that the slump of concrete decreases with the increase of rubber powder substitution rate, and the rheological performance results show that the friction force increases with the increase of rubber powder substitution rate. The compressive strength of concrete decreases with the increase of substitution rate. The results of ICP show that rubber powder will adsorb cations to affect cement hydration. Nanoindentation shows that the addition of rubber powder leads to the decrease of high-density hydration products. The results of SEM-EDS show that rubber powder will affect the Si/Ca of hydration products. The results of UPV and MIP are similar. The hydrophobicity of rubber powder and the poor compatibility with hydration products are the key factors affecting the durability of concrete. Because the rubber powder only needs to be ground to avoid the related process of cement, it can obtain good economic and environmental benefits. In practical engineering, rubber powder can be added appropriately.

This paper introduces an innovative methodology for evaluating the dry rubber content (DRC) of natural rubber latex (NRL) through the utilisation of transient hot wire (THW) technique. To accomplish this objective, an instrumentation system has been devised and implemented, which operates based on this underlying principle. The proposed approach capitalizes on the significant disparity in thermal conductivity between rubber particles (0.13 W/m-K) and water (0.58 W/m-K). A series of NRL samples obtained from the field were assessed using the developed instrument and their corresponding DRC values determined using conventional weighing-drying technique. The outcomes reveal a strong correlation between measured temperature increments for each sample within a predefined time frame and their respective DRC values. Furthermore, the proposed method offers the advantage of a significantly reduced measurement time, requiring only approximately 10 min to determine the DRC, in contrast to the existing weighing-drying technique, which necessitates around 18 h. Both techniques yield a measurement accuracy of ± 2%.

The influence of silver nitrate as an antimicrobial agent on natural rubber (NR) and nitrile butylene rubber (NBR) latex films were investigated. The NR and NBR latex films were prepared using coagulant dipping with an additional dipping procedure was performed prior to wet gel leaching to deposit the silver nitrate solution onto rubber films. Different concentrations of silver nitrate solution were used in the range of 2.5, 5.0, 7.5, 10.0, 12.5 and 15.0 mM, respectively. The degree of microbial inhibition efficiency of the antimicrobial NR and NBR on Staphylococcus aureus (S. aureus) which is a common nosocomial pathogen in combating hospital acquired infections (HAIs) were evaluated. The field emission-scanning electron microscopy (FE-SEM) analyses showed an obvious morphological transition of the silver particle structures were observed as the concentration of silver nitrate increased. On the other hand, the microbial inhibition study using free diffusion and dissipative equations are suggested to determine minimum inhibition concentration (MIC). The antimicrobial study suggested that silver nitrate deposited on the NR and NBR latex films were not influenced by the morphology of silver microstructure which yielded from different concentrations of silver nitrate deposited on latex films surface. Hence, the study effectively demonstrates that antimicrobial inhibition on different antimicrobial latex films results different of MIC values. The tensile strength results of silver nitrate treated NR and NBR latex films also showed no significant reduction on unaged and aged of film’s tensile strength, modulus at 300% (M300) and elongation at break (EB). These results indicated that the deposition of silver ion latex films had no negative effect on film’s integrity of the NR as well as NBR latex films.

The present study involves the fabrication of Poly (lactic acid) (PLA) blends with natural rubber (NR) or epoxidised natural rubber with 25% and 50% epoxidation levels (ENR 25 and ENR 50) respectively to produce flexible PLA filaments for fumed deposition modelling (FDM) 3D printing. Styrene-ethylene-butylene-styrene-grafted maleic anhydride (SEBS-g-MA) as a compatibiliser was used in the PLA/NR, PLA/ENR 25, and PLA/ENR 50 blends with a fixed blend ratio of 80/20. The effects of SEBS-g-MA content ranging from 5 to 15 parts per hundred polymer (php) in the PLA/NR, PLA/ENR 25 and PLA/ENR 50 blends on the thermal properties, tensile strength, elongation at break, melt flow index (MFI) and morphological analysis were studied. Differential scanning calorimetry (DSC) demonstrated that the glass transition temperature (T_g) and melting point temperature (T_m) of PLA shifted to a higher temperature as the SEBS-g-MA content increased in the PLA blends. Furthermore, a change in the degree of crystallinity was noted as the SEBS-g-MA content increased from 5 to 15 php, directly affecting the elongation at break of the compatibilised PLA blends. Relatively, the PLA/ENR 25/SEBS-g-MA blends have a much lower T_m, enthalpy, and crystallisation degree, indicating higher compatibility than the other compatibilised PLA blends. The results are consistent with the scanning electron microscopy (SEM) analysis, which revealed a possible interaction between the MA moiety, SEBS and rubber component functional groups. The MFI is gradually reduced with the addition of SEBS-g-MA up to 15 php; however, the value is comparable to the commercial PLA filament, which is sufficient for printability study. Overall, the PLA/ENR 25 containing 15 php SEBS-g-MA achieved optimal printability as a flexible PLA filament for 3D printing, as evidenced by a tenfold increase in elongation at break of the 3D-printed parts compared to the commercial filament.

The rubber tree (Hevea brasiliensis) is vulnerable to infections by various fungal pathogens. White root disease infection is one of the most prevalent diseases of rubber in Malaysia. This disease is caused by the fungus Rigidoporus microporus. Delayed management of this disease can cause considerable reduction in total tree stand and ultimately decreased land productivity. The utilisation of elicitor proteins to heighten host plant resistance represents a sustainable approach to disease control by reducing the use of chemical fungicides. The cerato-platanin protein family is the most widely reported class of elicitor proteins. This study isolated a member of the cerato-platanin family from R. microporus and evaluated its expression during H. brasiliensis infection. Total RNA was extracted from the mycelial sample of R. microporus followed by cDNA synthesis, isolation and cloning of the cerato-platanin transcript referred to as rmcp. In silico characterisation of the obtained sequence was then conducted and the relative expression of the gene was evaluated using RT-qPCR. A transcript of 438 bp encoding 145 amino acids protein, denoted as RmCP, was isolated and cloned. RmCP is composed of a cerato-platanin domain and a predicted N-terminal signal peptide. Phylogenetic analysis grouped RmCP into a cluster together with cerato-platanin proteins originating from basidiomycetes. The expression of rmcp gene was consistent throughout the study period and was not significantly different from axenic culture. This suggests the gene to have a fundamental function in the life cycle of R. microporus.

For a long time, skim latex has been regarded as waste from the latex centrifugation process. To recover the rubber, skim latex is coagulated using strong acid due to the high presence of non-rubbers, resulting in products of low quality and unpleasant odour. Additionally, the acid discharged into effluent ponds causes malodour and adversely affects the health of nearby residents. Considering this, a novel method employing a membrane filtration system was utilised, successfully recovering and concentrating skim latex while removing water-soluble non-rubbers. The resulting latex concentrate was then compared to raw skim latex in terms of latex, colloidal, and film properties. Latex properties, namely total solids content (TSC), dry rubber content (DRC), alkalinity, nitrogen content, and gel content were determined. For the colloidal properties, particle size and distribution, zeta potential, and rheological properties (flow and viscoelastic behaviours), were characterised. The film properties assessed included the swelling index, appearance, and tensile properties. Significant improvements in latex properties after concentrating were observed, with both TSC and DRC increasing to 42% and 36%, respectively, while alkalinity, nitrogen, and gel contents decreased to 0.61%, 2.23%, and 54%, respectively. Particle size distribution in raw skim latex (RSL) exhibited a tri-modal distribution, but after membrane filtration, concentrated skim latex (CSL) showed a bi-modal distribution with particle sizes ranging from 0.03 to 0.3 µm and 0.3 to 5 µm and average sizes of 0.07 and 1 µm, respectively. Changes were also noted in zeta potential and rheological behaviour after membrane filtration. The isoelectric point of zeta potential shifted to a higher pH, from 4.2 for RSL to 4.9 for CSL, and the absolute zeta potential values decreased with increasing pH values. CSL also demonstrated a different flow behaviour, fitting well to the Herschel-Bulkley model, unlike RSL, which conformed to the Bingham model. Membrane concentration resulted in significant increases in CSL yield stress, consistency index, and shear thinning behaviour, leading to higher moduli values and indicating increased interaction between CSL particles. Conversely, CSL films prepared via casting swelled more in toluene, approximately two times more than RSL films. Nevertheless, RSL films were more opaque and only became transparent after leaching, indicating high non-rubber contents. Regarding tensile properties, both unleached and leached CSL films exhibited a similar tensile versus elongation profile, with ultimate tensile strength and elongation at break values ranging between 1.4 and 1.6 MPa and 650 and 700%, respectively.

Methylene blue undergoes decomposition upon the exposure to ultraviolet (UV) light and oxygen to release reactive species such as singlet and triplet oxygen. These reactive species have adequate energy to oxidise and degrade organic materials including natural rubber (NR). In this work, NR latex was exposed to UV in the presence of methylene blue and hydrogen peroxide to produce low molecular weight NR latex. The Mn of NR was reduced from 544 × 10³ g/mol to about 6 × 10³ g/mol with low gel content. During the photodegradation, the NR chain was cleaved at both C = C and C-C bonds. The molecular structure of LNR was similar to that of the NR but with new functional groups of hydroxyl and carbonyl, resulting from oxidation and chain cleavage. The rubber particles were originally pear-shaped but changed to spherical after the degradation reaction, although their size remained largely similar.

The temperature change in rubber components during operation results in a change in its transfer function and affects service life. In this study, the phenomenon of self-heating and its effect on the resulting forces is examined experimentally under different loading conditions using a test rig that applies a rotating shear load. The observed phenomenon from the tests was modelled using a finite viscoelastic model based on the multiplicative decomposition of the deformation gradient. The simulation results of the surface temperature and the resulting forces using the implemented material model showed good agreement with experimental results. The test rig and the simulation model can be used to characterise rubber materials and therefore, allow the prediction of the temperature distribution and the transfer function of rubber components under operational conditions.

Semi-IPN composites of natural rubber (NR), hydrophilic sodium carboxymethyl cellulose (CMC) and carbon black (CB) with different compositions have been created by solution casting process in an attempt to develop a novel adsorbent under various pH ranges for the cationic dye methylene blue (MB). The produced NR/CMC film can be employed as an adsorbent of MB dye, according to the results, which demonstrate that composites with 2% CMC and 0.2 g CB displayed a maximum adsorption capacity of 1.72 mg/g and a dye removal efficiency of 85.22% at pH 9. The semi-IPNs were characterised using X-ray diffraction, Thermogravimetry, FTIR, and SEM methods. The NR/CMC semi-IPN composites' SEM micrographs showed a continuous, homogenous and porous structure. The films' equilibrium swelling characteristics were examined. For the NR98%CMC2% polymeric composition, containing 2% glutaraldehyde (GA) and 0.02 g CB loading, a maximum tensile strength of 3.3 MPa was achieved. In a 12-month period with 2% CMC, the NR/CMC semi-IPN showed a 70% biodegradation rate, while the pure NR showed only a 20% degradation rate. X-ray diffraction analysis shows that the addition of CMC reduces the crystallinity of natural rubber.

Rubber plantations are among the most important in the world's tropical regions. They play a positive role in carbon sequestration and in delaying climate change, supplying strategic resources of natural rubber (NR), and aiding in poverty alleviation and rural revitalisation. This paper reviews six methods of research on carbon sinks in rubber plantations: the biomass inventory method, the biomass conversion factor continuous function method, the trade potential of carbon sinks method, the calculation method for carbon storage of rubber latex, the eddy covariance method, and the remote sensing image model method. This study clarifies the carbon sink assessment and enhancement model for rubber plantations and describes the composition of the carbon pool, which includes the aboveground and belowground vegetation biomass carbon pools, litter carbon pool, latex carbon pool, and soil carbon pool. It also examines influencing factors such as tree age, global climate change, and human disturbance, as well as improvement pathways including afforestation, fertilisation, irrigation, and tapping, and evaluation methods like field surveys, positional observations, remote sensing monitoring, and model simulation. Research on carbon sequestration in rubber plantations faces challenges, including the unclear dynamics of carbon sources and sequestration, uncertain spatial and temporal patterns, and the long-term lack of accurate monitoring of carbon sinks and technologies for increasing sinks and reducing emissions. Future research should focus on the methodology of rubber plantation carbon sequestration projects, the dynamics of carbon sequestration, and the spatial allocation pattern of carbon sequestration in rubber plantations.