Search Results (118)

The incorporation of residues into rubber composites has gained attention as a sustainable strategy to address waste management challenges while replacing commercial fillers. In this study, we investigated the potential use of water filter cartridge residue after exhaustion, composed of activated carbon, as a reinforcing filler in vulcanized natural rubber composites. Samples were prepared with 5, 10, 15, and 20 phr (per hundred rubber) of residue and compared to unfilled natural rubber. Stress vs. strain tests reached 13.9 MPa of tension at rupture for composites containing 10 phr of carbon-activated residues, representing a 21.9% increase compared to natural rubber. Interestingly, the tension at rupture for NR/AC_10phr reached values close to those of NR/CB_5phr (with carbon black N330) attaining 14.4 MPa. These results indicate that, even at relatively low concentrations, the carbon filter can offer partial substitution for commercial fillers. Moreover, the use of activated carbon from filter cartridges as filler in rubber composites provides an environmentally favorable alternative to energy-intensive regeneration processes for activated carbon. Full article

The pressing issue of global warming has prompted industries to seek sustainable and renewable materials that can reduce the use of petroleum-based products. Natural fibers, as bio-based and environmentally friendly materials, offer a promising solution. In this study, ramie fiber, which is one of the strongest natural fibers, is used as reinforcement, and the mechanical properties of natural rubber composites are evaluated. The composites were fabricated using a vulcanizing technique at 150 °C, and the fibers were cut into different lengths (5 mm, 10 m, and 15 mm) and weights (15 g, 30 g, and 60 g). Mechanical performance tests, including tensile and tear strength and hardness, were conducted. The results showed that as fiber concentration increased, so did the curing time. Moreover, the composites with higher fiber concentration had higher strength. The composite with a 10 mm fiber length and 60 g weight showed the highest tensile strength (10.35 MPa). Maximum tear strength (52.51 kN/m) was achieved with 5 mm fiber length and 60 g weight. Hardness values reached up to 88 Shore A (10 mm fiber length and 60 g weight), indicating excellent wear resistance. The specimen with the highest tensile strength was subjected to scanning electron microscope analysis. The SEM analysis revealed that the composite had a ductile type of fracture with appreciable plastic deformation, confirming good fiber–matrix interaction. These findings underscore the potential of ramie fiber–reinforced natural rubber composites as sustainable, high-performance alternatives to petroleum-based materials in structural and vibration-damping applications. Full article

Natural rubber is a widely used biological polymer material because of its excellent comprehensive performance. Nevertheless, the performance of domestic natural rubber cannot meet the requirements for high-end products such as aviation tires, which has become a constraint on the innovation and upgrading of high-end manufacturing enterprises and the enhancement of global competitiveness in China. To solve the bottleneck problem of natural rubber processing technology, this study systematically analyzed the effects of different varieties of fresh latex ratios on the processing and dynamic properties of bio-coagulated natural rubber. By mixing PR107 and Reyan72059 fresh latex with Reyan73397 fresh latex according to proportion, the fresh latex was coagulated by enzyme-assisted microbials, and the effects of the fresh latex ratio on physical and chemical indexes, molecular weight distribution, vulcanization characteristics, processing properties, cross-link density and physical and mechanical properties of the natural rubber were analyzed. The results showed that the aging resistance of natural rubber coagulated with enzyme-assisted microbial decreased, and the aging resistance of natural rubber increased with the increase in the mixing ratio of PR107 and Reyan72059 fresh latex. The proportion of high molecular weight of the natural rubber coagulated with the enzyme-assisted microbial increased, and the fresh latex mixing had little effect on the molecular weight distribution curve. Under the carbon black formulation, the CRI of the enzyme-assisted microbial coagulated natural rubber compound was relatively larger. Under the same strain conditions, the H-3 compound (PR107:Reyan72059:Reyan73397 = 1:1:3) had the best viscoelasticity and the least internal resistance of rubber molecules. In addition, the cross-link density, tensile strength, elongation at break, and tear strength of H-3 vulcanized rubber were the largest, improved by 23.08%, 5.32%, 12.45% and 3.70% compared with the same H-2 vulcanized rubber. In addition, the heat generation performance was reduced by 11.86%, and the wear resistance improved. Full article

The motivation of this research was to analyze the dynamic properties, mainly the loss modulus, of vulcanized immiscible blends of natural rubber (NR) and styrene-butadiene rubber (SBR) in the glass transition zone, where the SBR phase is in a glassy state and the NR phase is in a rubbery state. The blends were cured at 433 and 443 K and studied around the glass transition using a dynamic mechanical analyzer. The dependence of the loss modulus on temperature was described by considering the phase separation, and the frequency dependence was also included to provide a deeper insight into the dynamic properties. This was achieved by integrating the mechanical model proposed by Zener, which considers a single relaxation time related to temperature using both the Arrhenius and Vogel–Fulcher–Tammann (VFT) relations. The best correlation with the data was obtained using the Arrhenius relationship. The activation energy of the NR phase increases with the NR content in the blend, while in the SBR phase, it varies slightly. The trends obtained are related to curative migration from the SBR to the NR phase, increasing the crosslink density at NR domain boundaries. These insights are valuable for optimizing the performance of these elastomeric blends in practical applications. Full article

This study investigates the recycling of ophthalmic lens waste (OLW) in the production of vulcanized natural rubber (NR) composites, aiming to promote sustainability and reduce costs. To this end, Vietnamese natural rubber and ophthalmic lens waste were used, varying the filler content from 0 to 50 phr. Rheological tests demonstrated that the addition of OLW decreases the cure time. The crosslink density, assessed through the Flory–Rehner and Mooney–Rivlin methods, exhibited an increase with the incorporation of a reinforcement. Thermal and spectroscopic analyses demonstrated the thermal stability of the composites and the absence of chemical interactions between the polymer matrix and the OLW. Mechanical tests showed that the composites exhibit satisfactory tensile and tear resistance, although the filler primarily acts as a filler rather than a structural reinforcement. Thus, the incorporation of OLW in NR composites emerges as a viable alternative for the reuse of industrial waste, fostering more sustainable and efficient practices in the polymer industry. Full article

The importance of sustainable polymers has increased greatly in the last years since most polymers are derived from non-renewable sources. Sustainable polymers (i.e., biopolymers) such as natural rubber (NR) are proposed as a solution for this concern. A comparative study between NR and deproteinized NR (DPNR) was carried out to elucidate the role of proteins on the network formation and degradation of peroxide cross-linked NR using time-domain NMR experiments. The ¹H multiple-quantum (MQ) NMR experiments provided information on the cross-link density and its spatial distribution, while the actual fraction of non-coupled network defects was obtained by exploiting the Hahn echo approach measured on swollen samples. The results showed that proteins influenced the network formation during the vulcanization process of NR, leading to a higher number of non-elastic network defects and promoting the creation of additional cross-links with a broader spatial distribution. The formation of network heterogeneities in different length scales deeply influences the mechanical properties of NR samples. On the other hand, the proteins showed a pro-oxidant activity on the degradation behavior by accelerating the degradation process of peroxide cross-linked NR. Full article

The growing interest in renewable resource-based materials has driven efforts to develop elastomeric biocomposites using biomass, phyto-ash, and biochar as fillers. These bio-additives, derived from beech wood through various processing methods, were incorporated into natural rubber (NR) at varying weight ratios. The primary objective of this study was to assess how the type and content of each bio-filler influence the structural, processing, and performance properties of the biocomposites. Mechanical properties, including tensile strength and hardness, were evaluated, while crosslink density of the vulcanizates was determined using equilibrium swelling in solvents. Additionally, the composites underwent thermogravimetric analysis (TGA) to determine the decomposition temperature of individual components within the polymer matrix. Bio-fillers influenced rheological and mechanical properties, with phyto-ash reducing viscosity and cross-linking density, and biochar and biomass increasing stiffness and maximum torque. Biochar extended curing time due to the absorption of curing agents, whereas phyto-ash accelerated vulcanization. Mechanical tests showed that all bio-filled composites were stiffer than the reference, with biochar and biomass (30 phr) exhibiting the highest hardness (45.8 °ShA and 49.1 °ShA, respectively) and cross-link density (2.68 × 10⁻⁵ mol/cm³ and 2.77 × 10⁻⁵ mol/cm³, respectively), contributing to improved tensile strength, in particular in the case of biochar, where the TS was 17.6 MPa. The study also examined the effects of thermal-oxidative aging on the samples, providing insights into the changes in the mechanical properties of the biocomposites under simulated aging conditions. Full article

The damping performance of chlorinated butyl rubber (CIIR) is exceptional; however, its poor processability during vulcanization can lead to numerous defects. Natural rubber (NR) and ethylene propylene diene monomer rubber (EPDM) were selected to blend with CIIR for improving its processing performance. Their effects on the vulcanization characteristics, mechanical properties, and damping performance were investigated. Blending CIIR with NR can considerably increase the vulcanization speed of the rubber compound and improve production efficiency. The tensile strength of the vulcanizate first increases with an increase in the dosage of NR in NR/CIIR, and subsequently, it decreases before increasing again. The tensile strength first increases and then decreases with an increase in the EPDM dosage in EPDM/CIIR vulcanizate. The tensile strength increases by 15.6%when the EPDM dosage is 60 and 80 phr. EPDM and NR have similar effects on the damping performance of CIIR, which were evaluated by fitting the data of loss factor (∆tanδ) versus NR or EPDM dosage. Therefore, the quantity of NR or EPDM can be conveniently calculated based on performance requirements when designing the formula of the CIIR matrix materials. Full article

This study examines the effects of mastication time and the addition of a plasticizer (acetyl tributyl citrate (ATBC)) on the properties of non-vulcanized polylactic acid/natural rubber (PLA/NR) blends using a factorial design, along with the impact of changing the weight ratio of the blends. The results reveal the formation of plasticized PLA (P-PLA)-based thermoplastics with enhanced ductility. ATBC functions as both a PLA plasticizer and a compatibilizer in the binary PLA/NR system. However, improving compatibility requires the exclusive use of masticated NR with an appropriate mastication time (60 min) before blending. Optimal properties are achieved at a P-PLA/NR weight ratio of 90/10, maximizing the impact strength (~35.40 J/m) and toughness (~7.21 × 10⁶ MJ/m³). However, higher NR contents lead to reduced mechanical performance due to poor interfacial bonding. Thermal analysis reveals superior miscibility and dispersion in blends with a lower NR content (10 wt%), while the addition of plasticizers and NR leads to a decrease in the glass transition temperature (T_g) of the blends. The results suggest potential applications for developing biodegradable products with enhanced flexibility and improved low-temperature performance. The incorporation of ATBC can enhance material properties without relying on conventional synthetic compatibilizers. Full article

Biomaterials interact with biological systems, influencing their responses. Different types of polymers—both natural and synthetic—are widely used in biomedical engineering, among a plethora of healthcare applications, to promote tissue regeneration. The natural rubber latex extracted from Hevea brasiliensis is a biopolymer that whose biocompatibility makes it a valuable study object. Its great regenerative properties are largely associated with the fraction FrHB1, which has demonstrated angiogenic and wound-healing potential by inducing blood vessel formation, collagen synthesis, and fibroblast migration—crucial factors for tissue repair. This study aimed to develop scalable methods for extracting and purifying the F1 protein fraction from industrialized natural latex for biomedical applications. We tested two types of industrial latex, bi-centrifuged and pre-vulcanized latex as well as 60% centrifuged natural latex to determine the most effective composition used in subsequent extractions and fractionation steps. Then, we isolated FrHB1 from the pre-vulcanized latex using selective precipitation, ultrafiltration, and affinity chromatography. The yield of the first batch of this serum was 40.62% with protein concentration of 1.52 ± 0.06 mg/mL. The second batch had a yield of 49.74%; however, due to results lying outside the analytical curve, its protein concentration could not be calculated. The yield of the third batch was 57.19%, and its protein concentration was 1.8477 ± 0.033 mg/mL. This approach facilitates large-scale therapeutic applications utilizing a commercially viable and accessible resource. Moreover, these findings highlight industrialized natural latex as a sustainable source of bioactive molecules, contributing to advancements in regenerative medicine and tissue engineering. Full article

Direct ink writing (DIW) is an economical, straightforward, and relatively energy-efficient 3D printing technique that has been used in various domains. However, the utilization of rubber latex for DIW remains limited due to its high fluidity and inadequate support, which makes it challenging to meet the required ink rheological characteristics for DIW. In this study, a concentrated pre-vulcanized natural rubber latex (CPNRL) ink with a high solid content of 73% without additives is developed for DIW 3D printing. The CPNRL ink is concentrated using superabsorbent polymer (SAP) beads, which demonstrates good colloidal stability, favorable rheological properties, and superior printability. The impact of printing angles on the mechanical properties of the rubber specimens based on the CPNRL-73 ink is explored in detail, wherein the tensile strength of the specimen printed at a 90° angle reaches an impressive 26 MPa and a strain of approximately 800%, which surpasses the majority of 3D-printed rubber latex specimens. Additionally, the CPNRL ink can be used to print a wide range of intricate shapes, demonstrating its advantages in excellent formability. The preparation of 3D printable ink using the absorption method will expand the application of elastomers in fields such as customized flexible sensing and personalized rubber products. Full article

Zinc oxide (ZnO) particles were successfully synthesized through the green method using aloe vera extract and zinc nitrate (1:1). The structure, morphology and properties of the biosynthesized ZnO (bioZnO) particles were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), time of flight secondary ion mass spectrometry (TOF-SIMS) and thermogravimetry (TG). The morphology and the size of ZnO particles were elucidated by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Then, the ability of bioZnO to activate sulfur curing of natural rubber (NR) was tested and compared to commercial ZnO traditionally used as vulcanization activator. The bioZnO showed similar activity in the vulcanization process to commercial ZnO. NR composites containing bioZnO were pro-ecological in nature and exhibited better mechanical characteristics and durability against thermo-oxidative aging than NR with commonly used micrometric ZnO. Moreover, NR vulcanizates containing bioZnO showed good mechanical properties in dynamic conditions and satisfactory thermal stability. The present research is new and in addition to the analysis of biosynthesized ZnO particles, the effect of the activator in the vulcanization process of the NR elastomer and its influence on the properties of the final products were additionally discussed. Full article

The substantial waste generated during the processing of hides and skins as well as at other stages of manufacturing is a recurring issue in the leather industry that this article attempts to address. To investigate the mechanical and thermal characteristics of the resultant composites, this study suggests using leather waste from the bovine leather industry, analyzes the tanning process, and assesses the viability of mixing this waste with natural rubber (TSR-20). Without the inclusion of leather waste, the resulting composites had exceptional tensile strength, surpassing 100% of rubber’s strength. The effective interaction of the recycled leather particles with the natural rubber matrix was evidenced using the Lorentz–Park equation. This better performance points to a competitive relationship between rubber and leather waste. The samples’ density was 10% greater than that of polybutadiene elastomers and 10% greater than that of natural leather, while the hardness was comparable to that of PVC, which is frequently utilized in the design of general-purpose soles. This suggests that waste from the leather industry can be efficiently utilized in sustainable applications, particularly in the production of leather goods and shoes, helping to valorize waste that is typically discarded. Furthermore, by encouraging the use of recycled resources in the creation of new compounds, this plan provides the rubber sector with a sustainable option. To optimize this proposal, perhaps will be necessary to identify different vulcanization systems to improve the physical mechanical properties and other uses derived from the optimizations realized. This composite can be applied in the fashion industry in order to develop new trends around the application of waste and residues for a natural design line. Through the research process, it was possible to integrate the residues into the natural rubber matrix, as evidenced in the characterization process. Full article

Ammonia is commonly used as a preservative in the production of concentrated natural rubber latex (CNRL) and latex products; however, it poses a serious risk to human health and the environment. In this study, we investigated a thioacetamide derivative (TD) as a preservative of ammonia-free CNRL and the optimization of a stabilization system comprising potassium hydroxide (KOH), lauric acid (LA), and sodium dodecyl sulfate (SDS) to enhance its preservation effect. The results revealed that an optimal amount of TD (0.03%) can effectively maintain the stability of CNRL, inhibit the increase in volatile fatty acid number (VFA number), maintain stable viscosity values, and improve the mechanical stability time (MST). However, increasing the TD dosage results in an increase in both the viscosity and VFA number and a decrease in MST. KOH was used to regulate the pH value of CNRL. It was also found that it can enhance considerably the mechanical properties of CNRL dry films and accelerates the vulcanization of vulcanized film; however, an excessive amount causes latex thickening. LA proved essential for improving the MST and reducing latex viscosity, thereby substantially enhancing the stability and processability of pre-vulcanized latex, but an excessive amount is detrimental to the curing speed and final mechanical strength. SDS can rapidly improve the MST and reduce the viscosity, but it negatively affects the surface molding of dry rubber films. In conclusion, KOH, LA, and SDS at appropriate dosages play a balancing and complementary role in the preparation of ammonia-free CNRL. Upon analyzing diverse performance metrics of CNRL, it has been determined that the optimal TD dosage ranges from 0.02 to 0.03% for maximum efficacy. The KOH dosage should be maintained within 0.1–0.15% to achieve the most favorable outcome, while the LA dosage is advisable to be kept between 0.06 and 0.1%. Full article

Herbal dust, a waste byproduct from filter-tea production, was annealed to form ash that can be incorporated into natural rubber as an eco-friendly filler. Three types of herbal dust ash (HDA), green tea, hibiscus, and lemon balm, were added at two different contents, 2.5 and 5 phr, into the rubber compound, while the content of carbon black, as a filler, was maintained at 50 phr in all samples. The impact of HDA type and content on the rheological and mechanical properties of rubber products was evaluated. Rheological analysis showed that HDA samples exhibited slightly lower maximum torque values (around 11.6 dNm) than ash-free samples (13.53 dNm), yet maintained vulcanization effectiveness with minimal impact on torque or cure rate metrics. Mechanical testing found that samples with 2.5 phr of lemon balm ash achieved comparable properties to samples without added ash, while samples with added hibiscus preserved crosslinking density and hardness. The addition of HDA led to decreases in tensile strength, elongation at break, and hardness values, with slight changes suggesting its applicability in similar industrial contexts. The findings highlight HDAs potential as a cost-effective, sustainable filler for rubber production, contributing to circular economy practices by repurposing significant amounts of tea waste into high-quality rubber materials. Full article