Journal of Rubber Research最新文献

It is well known that long-term chemicalised agricultural practices harmfully affect soil health and prevent sustainable management of fertility in crop fields, including that of plantation crops. Accordingly, an investigation was carried out to check how soil fertility characteristics such as soil pH, soil mineral nutrient and organic carbon content are altered in long-term chemicalised rubber plantations of Kerala, located in the ecologically sensitive Western Ghats of South India. Soil fertility status concerning soil types in the Rubber fields (USDA soil orders - suborders) such as Inceptisols - Oxic Dystrudepts (IOD), Ultisols - Ustic Haplohumults (UUH), Ultisols - Typic Kandiustults (UTK) and Mollisols - Pachic Argiustolls (MPA) involving six soil series are critically analysed. A negative impact of long-term chemicalised agriculture was visible in low soil pH and nutrient levels. In general, rubber fields in the region, even in the generally alkaline Mollisols, showed a pH of 6.23. The soils showed reduced nutrient and carbon content and a comparatively poor soil fertility index specific to soil types. The soil available NPK and soil total cations were found to be comparatively low and soil specific. However, rubber fields in Mollisols were significantly higher in STK, STMg, STCa, and STNa while those in Ultisols were significantly higher in SAP and SAK than other soil orders. The Inceptisols were significantly higher in SAN, STP, and soil organic carbon than others. Therefore, balanced fertilizer application concerning soil types per proper soil fertility monitoring has become significant to sustainable soil productivity management in rubber plantations.

This study aimed to identify stable and productive genotypes of rubber tree [Hevea brasiliensis (Willd. ex. Adr. de Juss. Müell-Arg.)] in water stress using the linear mixed model approach and to compare genetic parameters estimates of different genotypes groups in different years. The experiment was composed of 58 test clones and control clones (RRIM 600, GT 1 and PB 235) distributed across four trials evaluated in the Centro Avançado de Pesquisa e Desenvolvimento de Seringueira e Sistemas Agroflorestais, Votuporanga, São Paulo, Brazil. Rubber yield was evaluated over four years. The crop water stress index (CWSI) was used to evaluate water conditions over the period. The rubber yield data were analysed by the Restricted Maximum Likelihood model and Best Linear Unbiased Prediction (REML/BLUP) procedure. The plant development conditions were inadequate throughout the period. The effect of genotypes was significant in all analyses, indicating conditions favourable to the selection. The superior clones were V 051, V 006, and V 123 (Trial 1); V 227, V 263, and V 288 (Trial 2); V 744, V 619, and V 582 (Trial 3) and C 311, C 344, and C 33 (Trial 4). These genotypes can be used as parental clones in future breeding cycles. There are clones capable of maintaining yield stability in water deficit periods. The annual genetic variability estimated for rubber yield varies from year to year but is maintained during the breeding cycle. This contributes to the maintenance of the genetic variability among productive genotypes.

This paper describes the effects of incorporating the commercially available phenylurea-based antimicrobial agent S89 to pre-vulcanised natural rubber latex (NRL). The physical properties of the dipped film derived from the S89 incorporated into pre-vulcanised NRL such as antimicrobial efficacy, wettability properties, surface characteristics, surface morphology and tensile strength were further evaluated. The antibacterial activity of S89 in NRL films was tested using the agar disc diffusion method and S89 had been demonstrated to suppress and prevent bacterial growth even at low loading levels. Moreover, the minimum inhibitory concentration (MIC) of S89 was obtained by fitting the inhibition zone diameter and loading of S89 using two mathematical diffusion models, free and dissipative models. In this work, the dissipative model is shown to be the best-described diffusion model for S89. The leaching behaviour of S89 in an artificial sweat was investigated where the leachate of S89 is observed after 20 min of immersion at a very low concentration (0.039 ug/mL). Interestingly, NRL films incorporated with S89 displayed better wettability properties on air facing (AF) surface indicating that the AF surface of the film had been altered to be more hydrophilic. Nonetheless, there were no changes observed to the former facing (FF) surface. In addition, the polarity of the surface was also reduced which corresponds to the contact angle results. Further analysis of the Field Emission Scanning Electron Microscopy (FESEM) surface morphology on the NRL film incorporated with S89 exhibited sufficient miscibility and homogeneity during latex compounding with no agglomeration observed on both surfaces (air and former) and at the cross-sectional surface. Meanwhile, comparative tensile strength (of more than 20Mpa) of NRL films incorporated with S89 was observed for low dosage at 1 phr and 3 phr. In conclusion, antimicrobial natural rubber (NR) films for glove application with satisfactory tensile properties, adequate wettability properties, non-agglomerated surface morphology and good antimicrobial properties were achieved by employing a low loading of S89 in the NRL.

Evaluating the suppliers of an industry based on the sustainability and resilience of the supply chain (SC) has become one of the most attractive research topics in the world today. Meanwhile, the rubber industry is of fundamental importance due to the environmental effects and strengthening the resilience of its supply chain against disruptions. The main goal of the upcoming research is to design, extract and calculating of weight the determining factors in the sustainability and resilience of the supply chain and finally to select the best sustainable and resilient suppliers of the rubber industry by simultaneously applying the confirmatory factor analysis (CFA) approach and the decision-making techniques of SWARA (Step-wise Weight Assessment Ratio Analysis) and MOORA (Multi-Objective Optimization on the Basis of Ratio Analysis). For this purpose, in this research, a conceptual and integrated model of the supplier evaluation system based on sustainability and resilience factors has been extracted first by extensively reviewing the literature and research background. Further, in order to investigate the final determining factors in the integrated performance evaluation of suppliers, the confirmatory factor analysis (CFA) approach and the opinions of 40 experts in the rubber industry in Iran were used. The output of this approach showed that all the identified factors have a positive effect on the evaluation of suppliers. Then, by using the SWARA technique and using the opinions of 40 industry experts, the weight of the factors was calculated. The output of this technique showed that the third factor of supply chain sustainability, (S3: Strategy, support and commitment of company managers) with the highest weight is ranked first in terms of importance. Also, the 7th factor of sustainability (S7: Green warehouse) with the least weight in terms of importance in the integrated performance evaluation system of suppliers was placed in the 16th ranks. At the end of the research, 7 rubber industry suppliers were evaluated using the opinions of 40 experts and using MOORA's technique. The final result of this technique showed that the fifth supplier is ranked first, and the fourth supplier is ranked last. In this way, an integrated and comprehensive approach was proposed in order to measure and evaluate the suppliers of the rubber industry in Iran.

The rubber tree is an economically important tree planted in many tropical countries. While rubber planting has improved the livelihoods of growers, it has also resulted in soil degradation. However, systematic studies on assessment of soil health and its management in rubber plantations are limited. The present study explored whether intercropping of Michelia macclurei (an ornamental evergreen tree) in rubber plantation could help conserve soil health compared to traditional monoculture practice with randomised complete block design. The rubber tree density was the same in monoculture and intercropping, with the addition of Michelia macclurei in intercropping. The effects of soil properties and microbial communities was used to analyse two different planting patterns of rubber monoculture and rubber intercropping using soil sampling from field plots. The study investigated variation in soil physical structure, soil moisture, soil nutrients, soil microbes, and enzyme activities in two types of rubber plantations viz. a monoclonal plantation without intercrop (RM) and a plantation with Michelia macclurei as an intercrop (RAS). The results from above study showed an increase in soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (AN), available phosphorus (AP), nitrate nitrogen (NN) and total potassium (TK) in plantation with intercrop as compared to monoclonal plantation without intercrop. When comparing the corresponding values of RM to RAS, bacteria and total microbial abundance of RAS increased on average by 75.51% and 48.42%, respectively. In addition, after the transition from rubber monoculture to rubber agroforestry, the annual average of SOC, TN, AP, TK nutrients and pH in soil increased by 10.94%, 4.25%, 14.53%, 1.34% and 9.74%, respectively. Soil water content, soil bulk density and soil porosity were not significantly different between RM and RAS treatments. Sucrase activity and cellulase activity also increased in the RAS intercropping system. These results show that intercropping promotes soil organic matter and microbial communities and enhances soil enzyme activities. These findings indicate that rubber intercropping creates healthy soil environments conducive to tree growth and improves the ecosystem sustainability of rubber plantations. Healthier and stronger rubber trees may increase rubber production and provide sustainable management of plantations in the future.

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.