Synthetic rubber Ethylene Propylene Diene Monomer (EPDM) is extensively utilised throughout multiple sectors, especially for applications including seals, gaskets, hoses, and O-rings that directly interact with liquids. One of the challenges in using EPDM is improving its impermeability-related properties, which can be achieved by reducing the free volume within the material. This can be done by increasing the cross-link density, which is influenced by several factors, including the use of accelerators. This study aims to evaluate the effect of varying accelerator concentrations on the cross-link density of EPDM. Accelerators were added in different amounts: 0.6 phr (per hundred rubber), 1.2 phr, 1.8 phr, and 2.4 phr. The variations were analysed through rheology tests, tensile tests, cross-link density tests, and swelling tests. The findings indicate that the incorporation of accelerators markedly influenced the rheological properties of EPDM, with increased accelerator levels necessitating greater torque during processing. Tensile, cross-link density, and swelling tests indicated that the optimal accelerator concentration for achieving the best cross-link density and performance was 1.8 phr. Further increases in accelerator concentration did not necessarily lead to higher cross-link density, indicating that a higher accelerator concentration does not always guarantee better cross-linking results.
Natural rubber (NR)/acrylonitrile-butadiene rubber (NBR) blends suffer from poor interfacial compatibility, which limits their performance. In this study, epoxidised natural rubber (ENR) was used as a compatibiliser, whereas halloysite nanotubes (HNTs) and APTES-functionalised HNTs (AHNTs) (0–10 phr) were incorporated to enhance reinforcement. Surface functionalisation improved filler dispersion and interfacial adhesion through chemical interactions. At the optimum loading (6 phr), tensile strength increased by 129
With particular attention to awareness, perception, and adoption of recommended cultivation and processing practices, this study examined the spatial dynamics of technology adoption among the smallholder rubber farmers in Sri Lanka. The research analysed how neighbourhood effects influence different stages of the adoption process and the implications for policy using Moran’s I statistics, spatial econometric models, and spatial mapping. Significant positive spatial autocorrelation was found in both awareness and perception, demonstrating that knowledge and attitudes diffuse effectively through farmer networks and local interactions. By contrast, while adoption also exhibited statistically significant positive spatial autocorrelation, its degree of spatial clustering was markedly weaker than that of awareness and perception. Once individual-level covariates were controlled for in the spatial autoregressive model, the spatial dependence in adoption became statistically insignificant, suggesting that behavioural change is driven primarily by individual-level conditions rather than spatial contagion. However, farmers’ awareness and perceptions are strongly associated with adoption, indicating that while spatial proximity facilitates the spread of information and attitudes, the adoption decision is shaped by individual resources and farm-level conditions. The findings highlight a diffusion hierarchy; in particular, awareness and perception function as spatially driven precursors to adoption. Spatial spillovers could be leveraged by encouraging farmer-to-farmer learning, demonstration plots, and farmer organisations to fast-track the diffusion of knowledge and attitudes. Simultaneously, targeted measures should be employed to overcome constraints that hinder adoption, such as limited credit access, input support, and assistance with labour-intensive practices.
This study explores the effect of using citric acid (CA) as a sustainable, non-toxic alternative green co-crosslinker in the preparation of pre-vulcanised ENR/CA/S blend films. The work also focuses on achieving complete pre-vulcanisation within 24 h by optimising both compounding time and maturation time. Results show that increasing the compounding time to 4 h reduces the toluene swell index (TSI) to 1.70. The incorporation of 5–10 phr of CA, in combination with sulphur, contributes to improved crosslinking characteristics, as reflected by a reduced TSI value and enhanced mechanical properties. However, pH remains the primary factor governing crosslink density, while CA plays a secondary role by promoting additional interactions within the network. The pH of the ENR/CA/S latex decreases as CA content increases. A low pH at high CA content significantly reduces both mechanical strength and thermal stability of ENR/15CA/S. The pre-vulcanised ENR/5CA/0.9S exhibits the optimal performance, with a tensile strength of 4.18 MPa and a glass transition temperature (Tg) of –21.77 °C. This work highlights the potential of CA as a vulcanising supportive crosslinker in a sulphur-based vulcanisation system for latex applications, which opens new possibilities for developing diverse latex-dipped products.
Mechanical, thermal, tribological, flammability, and water absorption behaviours of vinyl ester composites under varied service temperature circumstances are examined in this work in relation to the influence of Citrus maxima peel-derived biochar and asparagus bean stem fibre treated with KOH–silane. To improve interfacial compatibility, the biochar was modified using a combination of alkali and silane treatment after being created by controlled pyrolysis. Using 50 °C and 70 °C as service temperatures, composites were made with biochar loadings ranging from 1 to 5 vol
The rubber industry is under increasing pressure to reduce its environmental footprint while maintaining high material performance and industrial scalability. This review examines recent advances in sustainable rubber compounding, focusing on green ingredients such as bio-based fillers, recycled carbon black, renewable plasticisers, and environmentally benign vulcanisation systems. Particular emphasis is placed on structure–property relationships, highlighting how bio-derived functional groups influence filler–rubber interactions, crosslinking behaviour, and viscoelastic performance. Recent studies demonstrate that partial substitution of conventional petroleum-based additives with sustainable alternatives can achieve comparable mechanical performance, improved ageing resistance, and reduced environmental impact when formulation strategies are carefully optimised. Industrial case studies further demonstrate the growing commercial viability of these materials. Key challenges remain in achieving consistent material quality, ensuring compatibility with existing processing technologies, and balancing performance trade-offs. This review provides a formulation-oriented perspective and outlines future directions toward scalable, high-performance, and environmentally responsible rubber materials.
Quebrachitol (QCT) is a sweet crystalline, optically active, naturally occurring compound that can be found in Allophylus edulis plants and has since been found in other plants such as Hevea brasiliensis, Cannabis sativa, and Paullinia pinnata. Its abundant presence in Hevea brasiliensis latex serum, combined with its diverse pharmacological activities, underscores its dual significance: as an indicator of plant metabolic processes and as a high-value bioproduct for health applications. Over the past decade, QCT was found to have potentially positive effects on treating human-related diseases. This review provides an updated overview of the medicinal properties of QCT by examining recent pharmacological research, evaluating its therapeutic potential, and highlighting key directions for future investigation. Over the years, various studies have reported a range of pharmacological effects of QCT, such as antidiabetic, antioxidant, antimicrobial, and its effects on osteoporosis, proposing the idea that QCT is a candidate for novel therapeutic agents acquired from natural sources. Additionally, this review will also identify existing knowledge gaps to help promote further investigation and research of its usage in therapeutic development and clinical applications. Furthermore, the recovery and utilisation of QCT from latex waste streams align with current industrial trends emphasising sustainability, circular economy, and green technology. By valorising this underutilised compound, the rubber industry can contribute not only to environmental stewardship but also to the advancement of natural-product-based therapeutics.
This study applies a quantitative methodological approach to evaluate the effects of collagen-based protein and kenaf core fibre biomaterials on the thermal stability, ageing behaviour and shelf-life performance of nitrile-dipped films. Commercial nitrile gloves, unfilled nitrile films and biomaterial-filled films were subjected to accelerated heat ageing from 50 to 80 °C, and tensile strength retention was used to characterise degradation. Activation energies and shelf-life predictions at 30 °C were estimated using the Arrhenius formalism, enabling a comparative kinetic assessment of the different formulations. The mathematical analysis revealed apparent differences in degradation kinetics: collagen-filled films exhibited the highest activation energy of 110.9 kJ/mol and the longest predicted shelf life of 6.1 years, reflecting improved interfacial compatibility and a more uniform microstructure that enhanced thermo-oxidative resistance. Kenaf-filled films exhibited a lower activation energy of 103.5 kJ/mol and the shortest shelf life of 2.3 years, consistent with weaker matrix adhesion and reduced dispersion. Commercial gloves and unfilled films exhibited comparable activation energies, approximately 105.5 kJ/mol and 103.4 kJ/mol, respectively, and predicted shelf lives of approximately 2.8 years. These kinetic parameters were consistent with thermogravimetric and microscopic observations, thereby validating the mathematically derived trends: greater thermal stability in protein-filled films and faster structural breakdown in kenaf-filled films. Overall, this work demonstrates how the Arrhenius-based kinetic analysis provides a framework for interpreting ageing behaviour in nitrile films incorporated with biomaterials. The results highlight the significance of biomaterial–matrix interactions in engineering nitrile-based materials with tailored durability or degradability, providing a foundation for designing more sustainable nitrile-dipped products.
Ammonia-free natural rubber (AFNR) latex offers a safer alternative to conventional ammonia-stabilized latex. While sulphur-based pre-vulcanization is effective, peroxide pre-vulcanization is challenging due to surfactant barriers and the free-radical nature of the reaction, which can limit crosslinking efficiency. This study investigates ultrasonic-assisted peroxide pre-vulcanization of AFNR latex to enhance peroxide decomposition and radical dispersion. Ultrasonic treatment increased crosslink density from 1.28 × 10⁻5 to 1.40 × 10⁻5 g·mol⁻1·g⁻1 and tensile strength from 5.1 MPa to 14.1 MPa compared to non-sonicated films, with elongation at break reaching 920
China faces a critical deficit in natural rubber self-sufficiency, exposing the industry to considerable security risks. As smallholder natural rubber plantations represent a vital component of the sector, research on natural rubber farmers’ productive behaviour is crucial for stabilising the industry. A systematic literature review was conducted, entailing rigorous coding and analysis of selected publications. The review identified 173 distinct influencing factors across 328 reference points, culminating in the development of the Farmer-Production-Society-Market-Rubber-Psychology-Policy-Nature (3P-FMNRS) framework, which elucidates natural rubber farmers’ decision-making mechanisms. Four case studies in Yunnan and Hainan provinces demonstrated the framework’s robustness in capturing how these factors synergistically and interactively shaped behavioural outcomes. The 3P-FMNRS framework provides a foundation for future systematic and empirical research on natural rubber farmers’ productive behaviour and offers actionable insights for policymakers to design targeted strategies to secure strategic natural rubber resources.
Given the challenges associated with prolonged monoculture rubber cultivation and the volatility of rubber prices, rubber crop diversification has been proposed to improve the livelihoods of rubber farmers, particularly those facing poverty and food insecurity. However, the adoption of such practices remains limited in Thailand. While crop diversification on rubber farms significantly enhances household food availability, its specific effects on food expenditure remain underexplored. This study examines how crop diversification adoption influences the level and structure of rubber farmers’ food expenditure. Using national household-level data collected from a stratified random sample of 1552 households between 2012 and 2014, and applying propensity score matching, the findings indicate that rubber crop diversity has a statistically significant positive effect on food expenditure, increasing annual per capita food expenditure by 1362–1418 baht. Additionally, rubber crop diversity promotes self-produced food consumption by 399–506 baht per person annually, thereby enhancing dietary resilience and food security for farmers. These findings provide a more comprehensive understanding of rubber crop diversity and the empirical support for implementing crop diversity policies to ensure the long-term sustainable growth of Thailand’s rubber industry.
Natural rubber production faces significant challenges in replanting and maximising yield. Conventional mature bud-grafting (MB) often suffers from inconsistent performance caused by rootstock heterogeneity and potential yield loss when the graft union enters the tapping window. This study evaluates the long-term field performance of elite Hevea brasiliensis clones using three rejuvenated plant types: in vitro plants on their own roots (IV), juvenile cuttings on their own roots (JC), and juvenile buddings (JB) onto seedling rootstock, against the mature budding onto seedling rootstock (MB) standard. We conducted large-scale randomised field trials in Ivory Coast comparing the performance of two commercially significant clones, RRIM600 and PB235, over five and six years of tapping, respectively. While RRIM600 demonstrated superior vegetative vigour (girth and conicity) with juvenile methods, the cumulative rubber yield over 5 years did not differ significantly from MB. In contrast, the high-yielding clone PB235 demonstrated a statistically significant advantage: JC yielded 15
Strong interfacial adhesion between the filler and polymer matrix is essential for developing high‑performance composites. In this work, ethylene–propylene–diene monomer/styrene–butadiene rubber blends were reinforced with multi‑walled carbon nanotubes (CNTs) functionalised with the imidazolium‑based ionic liquid 1‑butyl‑3‑methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI), hereafter referred to as BMI@CNTs. Filler–matrix interactions were examined through mole percent uptake (MPU) measurements in various solvents, while cure characteristics were evaluated using a moving die rheometre. Mechanical performance was assessed via tensile, tear, and hardness testing, complemented by swelling resistance, compression set, and crosslink density analyses to determine the effect of BMI@CNT incorporation. Increasing CNT loading elevated torque values and shortened cure times. Tensile strength and 100
Although several microbial strains can metabolise poly(cis-1,4-isoprene), recent studies suggest that tyre and road wear particles (TRWP) persist beyond 2 years in soil or water. To understand how microbial degradation evolves with increasing material complexity, the biodegradation of various elastomers, model composites and laboratory-wear particles was evaluated over several weeks using standardised tests in soil, compost, or freshwater. Natural rubber (NR) and synthetic poly(cis‑1,4‑isoprene) (cis‑IR) showed substantial biodegradation. NR reached 50
Xylanase enzyme hydrolysed nanocellulose (NC) from Acalypha hispida (A. hispida) leaves was functionalised with Cassia fistula seed gum (CFG), a natural polysaccharide, to enhance the interfacial bonding and technological properties of elastomeric composites. NC and CFG functionalised NC (CFGNC) were incorporated into Carboxylated Nitrile Rubber (XNBR) latex to fabricate nanocomposites. Structural and morphological analyses confirmed strong interfacial adhesion and uniform dispersion of NC and CFGNC within the XNBR matrix. The tensile strength of the nanocomposites increased significantly with the addition of 2 phr (parts per rubber) of NC and 3 phr of CFGNC, showing improvements of 71
Nigeria’s rubber sector holds considerable potential to contribute to economic diversification, rural employment, and sustainable industrial development, yet it remains underproductive due to persistent structural and institutional constraints. This study employs a mixed-methods empirical approach to examine the key factors that limit productivity and value chain development in Nigeria’s rubber industry, and to identify evidence-based policy pathways for sector revitalisation. Primary data were collected from 200 smallholder rubber farmers across five major producing states and 30 industry stakeholders, complemented by secondary literature. Quantitative analysis, including regression modelling, was used to identify determinants of rubber productivity, measured as latex output per hectare per year, while qualitative interviews provided institutional and market-level insights. Results indicate that ageing plantations, limited access to credit, weak extension services, and climate variability are the most significant constraints affecting smallholder productivity. Regression results show that access to credit, adoption of high-yielding clones, extension services, and climate-resilient practices are all statistically significant predictors of productivity. Stakeholder perspectives further highlight systemic bottlenecks, including inadequate processing capacity, weak market linkages, and the absence of a coherent national rubber development framework. The study concludes that Nigeria’s rubber sector is constrained not by agro-ecological limitations but by coordination failures across biological rehabilitation, finance, knowledge systems, and institutional governance. Scenario-based analysis suggests that under coordinated policy reform and targeted investment, Nigeria could substantially expand its participation in global natural rubber markets over the medium- to long-term. The findings provide policy-relevant insights for designing integrated strategies to enhance productivity, resilience, and sustainable value chain development.
Atomic Force Microscopy (AFM) is a sophisticated imaging technique to study the surface morphology of substrates in high resolution. Through phase imaging, AFM can be employed to probe the distribution of materials on a surface based on certain material properties. Natural rubber (NR) is often mixed with other materials, including fillers or other polymers, to achieve new or composite materials for specific applications. The objective of this study was to provide supporting data for mechanical testing results. Synthetic rubber (SR) is one of the common materials for blending with NR. NR-SR blends were prepared by mixing the two materials in the latex stage mechanically for 24 h before the dipping process. The dried dipped films remained on the glass formers and were subjected directly to AFM imaging using a Park System NX10 AFM. Both the topography and phase imaging images were recorded simultaneously. The process of capturing AFM images, as well as the image analysis, is presented in this report. With significant variations in mechanical properties, the phase imaging can differentiate NR from SR, and hence the distribution of each rubber can be visualised. The distribution pattern of these two types of rubbers appeared differently if a compatibiliser was added, as shown by AFM phase imaging.
Porous powder microspheres derived from epoxidised natural rubber latex (ENRL) were synthesised via a two-stage aqueous process involving epoxide ring-opening and free-radical polymerisation techniques. Through epoxide ring-opening chemistry, the epoxide groups were ring-opened when reacted with maleic anhydride (MA) to give ester crosslinks between ENRL polymer chains. The presence of ester groups was validated by Fourier transform infrared spectroscopy (FTIR) analysis. Additionally, the ester crosslinks increased the glass transition temperature (Tg) of unmodified ENRL from − 39 to − 6 °C for the crosslinked variant. ENRL particles with ester crosslinks were observed, illustrating an average particle size diameter between 30 and 45 μm, in comparison to the unmodified ENRL average particle size, which ranged from 0.3 to 1.3 μm. To produce porous powder particles, the ester-crosslinked ENRL, acting as precursor, was subjected to free-radical polymerisation using 3-(trimethoxysily)propyl methacrylate (TMSPMA) in the presence of ammonium persulphate (APS) as the radical initiator. Free-flowing powders were in the form of particle assemblages with a cauliflower-like morphology, resulting from the fusion of particles into random arrays and densely packed structures were produced. The powder exhibited a mean pore size of 6 nm, a specific surface area of 43 m2 g−1 and a specific pore volume of 0.06 cm3 g−1, hence classifying them as mesoporous materials with the potential for narrow-slit pores. The porous powder exhibited particle size distribution between 20 and 120 μm, with an average particle size at 105 μm. The Tg value increased to 42 °C compared to the precursor. FTIR spectra revealed a prominent signal around 1700 cm−1, along with broad overlapping signals in the range of 900–1200 cm−1, consistent with the presence of polymethacrylate and Si–O–Si networks, respectively. This novel material will create new opportunities for the exploitation of ENRL as a renewable polymer resin, significantly broadening its application potential beyond traditional uses.
This study focuses on the development of natural rubber-based tyre tread formulation with low rolling resistance and antistatic properties. The antistatic and rolling resistance properties of the tyre tread formulations prepared with polypyrrole as functional additive is compared with the standard formulation. Conducting polypyrrole (PPy) was synthesised via chemical oxidation of pyrrole using p-toluenesulfonic acid (p-TSA) as dopant and ammonium persulfate (APS) as the initiator and as synthesised polypyrrole was characterised using IR, XRD, TGA, and FESEM analyses. Both doped (PPy) and dedoped (dPPy) forms of polypyrrole were used as conductive reinforcing additives to enhance performance characteristics. Various loadings of PPy and dPPy were incorporated into the base formulation by partially replacing carbon black (CB) to enhance the antistatic property and low rolling resistance property. Truck tyre tread compounds were prepared by replacing CB with 5, 10, and 15 phr of dPPy as the conducting form of polypyrrole adversely affect the curing properties of the compound. The low rolling resistance property of the tread formulation was studied through temperature sweep in dynamic mechanical analysis, and improvement in antistatic properties via conductivity study. The incorporation of dPPy significantly improved the antistatic behaviour and it reduce the low rolling resistance by up to 40
The pyrolysis of End-of-Life Tyre (ELT) to produce recycled carbon black (r-CB) is well accepted globally as one of the efficient means to combat pollution and improve waste management related to the environmental carbon footprint. Currently, the high ash content inherent in the r-CB is a major concern for rubber compounders. The high ash content in r-CB is mainly composed of carbonaceous materials, silicone dioxide and zinc oxide that might interfere with the sulphur-vulcanisation reaction. The first step in addressing this concern was to evaluate the influence of high ash on the cure characteristics of Natural Rubber filled with r-CB. These characteristics would throw some light on the extent of crosslinking that is affecting the physical properties of the vulcanised rubber. Two natural rubber compounds were prepared, one was filled with r-CB having high ash, and the second was filled with HAF black having very low ash. The loading was fixed at 50 phr. The cure characteristics test using the oscillating disc rheometer was done at 150 °C. The results showed that the r-CB-filled NR compound gave lower minimum torque (Tmin) and lower maximum torque (Tmax) than that of the HAF-filled NR compound. The difference in torque ΔT of the r-CB-filled compound was only 52
