Journal of Rubber Research最新文献

Areas identified as escape zones for Pseudocercospora ulei, the causal agent of South American Leaf Blight (SALB), are being sought for the development of profitable rubber growing, as high-yielding Asian clones can be grown there without suffering repeated defoliation caused by epidemics of the disease. A performance trial with 10 clones was set up in 2006 in such an escape zone in Ecuador with non-American clones whose high production potential is acknowledged elsewhere in the world, some of which are recommended on a commercial scale. Production results over seven years, between 2013 and 2019, indicated a very high potential for this material in this new region, reaching average yields of 2.5 t/ha/year for clones PB 280, PB 312 and PB 314, and 1.85 t/ha/year for the control clone RRIM 600, despite a very pronounced 5-month dry season. However, the risks of wind damage and tapping panel dryness were found to be very high for PB 312 and PB 314. Clone PB 280 proved to perform best overall, with 93% of trees in production and one of the lowest Tapping Panel Dryness (TPD) rates. This clone, distinguished by its medium high latex metabolism and a high sucrose reserve, presents a highly promising alternative for the cultivation of rubber trees in escape zones. This is particularly relevant in situations where the phytosanitary risk associated with P. ulei is constrained.

A novel accelerator, cerium cysteine (Ce-Cys) was synthesised by double replacement reaction. The complex was characterised by FT-IR analysis, thermal analysis, EDTA titration and elemental analysis, respectively, to determine that the molecular formula of the complex was Ce (Cys)₃Cl₃·3H₂O. Cure characteristics, crosslink density, mechanical properties and thermo-oxidative ageing of NR compounds were investigated. The research revealed that the vulcanisates containing Ce-Cys manifested high scorch time, outstanding mechanical properties, and better thermo-oxidative ageing properties. Furthermore, based on kinetic calculations, it was concluded that as the amount of Ce-Cys increased, the reactivity of the crosslink precursor increased while the activation energy decreased.

Natural rubber (NR) is an invaluable material, in great demand for manufacturing of broad-ranging products. Its performance and properties have been widely studied by incorporating with different ingredients and inorganic fillers including clay minerals to develop many products, one of which is rubber floor mat. Nevertheless, the study on the pottery clay with NR from Cambodia is limited. This study investigated on the mechanical, impact absorption and morphological properties of clay-filled NR at different loadings for floor mat application. It was found that the effect of clay loadings on hardness of rubber composites was insignificant while the value of tensile strength and elongation at break before ageing was reduced to about 10 MPa and 720%, respectively, as clay loadings increased. For tensile properties after ageing, heat resistance property was obtained at clay loading of 20 and 30 phr. The value of tear strength was reduced as clay loading increased by reasons explained through SEM images that revealed agglomeration of clay filler within the rubber matrix accountable for the reduction in mechanical properties. The impact energy absorption showed optimum level at 10 phr of clay loadings at the value of 3.0 Joules. Compared to two types of commercial floor mats, the compounded composites showed superior performance in tensile properties and impact absorption ability.

Pestalotiopsis leaf fall disease (PLFD) has been on the increase in recent years, resulting in diminished latex yield in many rubber producing countries. Thus far, some reports have pointed to the presence of fungal pathogen(s) other than Pestalotiopsis sp. in the diseased leaves. To decipher the diversity of fungal pathogens, a total of 110 early-stage and another 110 late-stage symptomatic leaves were sampled from 12 Hevea clones in seven different areas in Malaysia during wintering and wet seasons at different times of the year. A total of 487 fungal isolates were obtained; 241 were from the early-stage and 246 from the late-stage symptomatic leaves. These isolates were clustered into 11 morphotypes based on colony appearance and microscopic observation of the spore. The diversity analysis revealed significant differences in morphotype richness and evenness when comparing different rubber clones, seasonal effects, and locations by which the fungal isolates were sampled. Five isolates representative of the five predominant morphotypes associated with PLFD were analysed using the Internal Transcribed Spacer (ITS) markers and BLAST analysis. Their closest relative species were identified as Colletotrichum conoides, Neopestalotiopsis surinamensis, Lasiodiplodia theobromae, Phyllosticta fallopiae and Letendraea cordylinicola. This study enhanced our understanding of PLFD, particularly the diversity and distribution of fungal communities associated with the disease across different rubber clones, seasons, and locations in Malaysia. The identification of these fungal isolates associated with PLFD symptoms paves the way for further research into their pathogenicity and the development of targeted management strategies to mitigate the disease.

Non-linear rheological behaviours of high fluorine content fluoroelastomer (HF-FKM) mixtures with varied carbon black (CB) filling amounts were investigated. Non-linear viscoelastic characteristics of HF-FKM mixture are characterised by large amplitude oscillatory shear (LAOS) tests, correlations between rheological behaviour and CB content were then discussed. Each non-linear viscoelastic parameter of HF-FKM mixture presents a three-stage characteristic with increasing CB content, corresponding to ranges of 0–20 phr, 25–30 phr, and 35–45 phr. Three stages of viscoelasticity characteristics for HF-FKM mixtures were considered to depend on the alteration of CB-elastomer network structure with increasing CB content, corresponding to the states where continuous phase of gum, CB-elastomer mesophase and excessive CB agglomerates predominate in mixture compound, respectively. After vulcanisation, samples with 30 phr CB content show the best resilience performance against thermal ageing, contributing to the existence of CB-elastomer mesophase. Samples with 25 phr CB content possess the second lowest compression sets at 225 and 250 °C ageing conditions but perform no better than those with 35 phr at 275 °C. The reason is presumed to be that the presence of excessive CB agglomerates in HF-FKM vulcanisate reduced irreversible deformation of the CB-elastomer network under compression at elevated temperatures.

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.