Rubber Research Articles

Effect of organic solvents on the functionalization of liquid natural rubber by iron salt-mediated chloro-nitro reaction

This study presents the functionalization process and the effect of organic solvents on the iron salt-mediated chloro-nitro reaction. The product obtained from the reaction is the chloro-nitro compound of liquid natural rubber (Cl-N-LNR). LNR functionalization was achieved by NO2Cl radical formed from iron(III) nitrate nonahydrate and iron(III) chloride in various organic solvents including ethyl acetate (EtOAc), tetrahydrofuran (THF), and dioxane (DOX). Fourier-transform infrared spectroscopy (FT-IR) was used to evaluate the structure of the resulting Cl-N-LNR. The degree of functionalization with the nitro group is 13÷15% mol units of Cl-N-LNR and the efficiency of the chlorine-nitration reaction is 80÷90%. Depending on the type of solvent used for the reaction, the structures of the functionalized chains received are disparate. Notably, the Cl-N-LNR is made in a THF/DOX solvent mixture that exhibited superior properties compared to the other solvents.

Rheological analysis of network structure of raw natural rubber prepared by different processing techniques

The performance of raw natural rubber (NR) is dominated by its network structure, particular the levels of long chain branching (LCB) and entanglement. Here, three type of raw rubbers were prepared using different processing methods for commercial grade NRs. Linear and nonlinear viscoelastic behaviors, as well as stress relaxation, were analyzed to access their network structures. The third relative harmonic, phase angle, and first to second quarter-period integral ratio of stress curve were utilized as indicators for the nonlinearity of samples. By combining these values with flow activation energy and characteristic times, it can be confirmed that naturally coagulated NR showed higher elasticity than acid-coagulated NR due to high levels of LCB and entanglement, and hot air drying could lead to chain degradation. These findings correlated with molecular weight parameters, gel content and Mooney viscosity results. This research establishes a method for monitoring raw NR quality and predicting its properties.

Comparative Study of Interfacial and Conventional Techniques for Nanosilica Incorporation in Natural Rubber Latex-Based Composites with Varied TEOS Content

This study investigates the preparation of natural rubber latex (NRL) composites with varying nanosilica contents of 5, 15, 30, and 45 phr, using both interfacial and conventional mixing techniques. Analysis focused on viscosity, plasticity, morphology, and FTIR spectra to evaluate the impact of these methods on composite properties. The interfacial techniquemaintained lower viscosity values, indicating better latex stability, and achieved higher silica yields and conversion rates (94 - 99%) at elevated TEOS contents. Plasticity analysis revealed that the interfacial method produced more uniform and stable plasticity values, suggesting improved resistance to oxidation and enhanced mechanical properties. SEM and FTIR analyses confirmed superior dispersion with the interfacial technique, especially at higher silica contents. These findings highlight the efficacy of the interfacial technique in optimizing the properties of NRL composites, making it a promising approach for advanced material applications. HIGHLIGHTS Analysis of interfacial and conventional mixing techniques reveals their impact on NRL composite properties, demonstrating the interfacial method's superior stability, silica dispersion, and enhanced mechanical properties. The interfacial method maintains lower, stable viscosity, prevents latex destabilization, achieves higher silica yields, and ensures economic and sustainable production of high-quality composites. SEM and FTIR analyses confirm better silica dispersion and morphology with the interfacial method, enhancing composite performance, durability, and informing industrial applications and future research directions. GRAPHICAL ABSTRACT

A Molecular Dynamics-Based Approach to Study the Effect of Covalently Bonded Modified Graphene on the Heat Transport Properties of Graphene/Natural Rubber Composite Material Interfaces.

Due to its excellent thermal conductivity, graphene can have great potential in the thermal conductivity of rubber composites. However, the interfacial thermal resistance between graphene and rubber severely hinders this application. In this work, molecular dynamics methods were used to study the interfacial thermal transport of carboxylated, aminated, hydroxylated, and oxy-bridged graphene in rubber composites. The results showed that the covalently bonded modified graphene significantly improved the thermal conductivity of the composites, with increases in thermal conductivity of 156.56%, 86.83%, 60.71%, and 44.28% and decreases in interfacial thermal resistance of 41.84%, 34.72%, 31.86%, and 16.74%, respectively. By calculating the phonon densities of states of different functionalized graphenes, it was found that covalently bonded functional groups increased the phonon match between graphene and natural rubber. However, when the degree of functionalization was greater than 11.96%, the phonon match was maintained at a stable value, which was why the covalently bonded modified graphene could significantly reduce the interfacial thermal resistance. Moreover, the graphene modified by covalent bonding was more uniformly distributed inside the natural rubber. The results of this study provide important theoretical guidance for preparing graphene/natural rubber composites with high thermal conductivity.

How Do Active Chain Density and Cross-Link Length Influence the Mullins Softening in Filled and Unfilled Natural Rubbers?

How Do Active Chain Density and Cross-Link Length Influence the Mullins Softening in Filled and Unfilled Natural Rubbers?

Toughening Polylactic Acid with Epoxidized Natural Rubber via Altering the Dicumyl Peroxide Mixing Sequence

Toughening Polylactic Acid with Epoxidized Natural Rubber via Altering the Dicumyl Peroxide Mixing Sequence

Recyclable sulfur cured natural rubber with controlled disulfide metathesis

Traditionally, sulfur-cured natural rubber compounds exhibit limited recyclability due to a significant drop in mechanical performance after reprocessing. Maintaining physical and chemical properties after recycling of a cross-linked polymer is an essential requirement for the global rubber industry to become more sustainable. Here, we demonstrate that tuning the curing process to favour a reversible cross-linked network based on disulfide and polysulfide bonds enables recyclability. We use a sulfur-based vulcanization system optimized with copper (II) methacrylate at concentrations of 2.47, 4.94, and 9.89 phr to control disulfide metathesis at low temperatures and enhance recyclability. Mechanical characterization identifies 2.47 phr as optimal for maintaining mechanical properties after initial moulding and full recovery after recycling. Additionally, we demonstrate that copper (II) methacrylate can be incorporated into existing rubber waste streams to promote recyclability.

High‐Performance Flexible Gas Sensor Using Natural Rubber/MXene Composite for Selective and Stable VOC Detection

AbstractFlexible gas sensors are gaining interest for real‐time volatile gas monitoring. A natural rubber (NR)/MXene nanocomposite sensor is developed. Among the six selected target volatile gases, the composite sensor exhibited a strong response value (82% toward 100 ppm NH3) with the fastest response/recovery time (12.3 s/15.5 s) to NH3. The sensitivity showed a clear dependence of gases, suggesting a good selectivity to varying gases. Ti3C2Tx MXene gas sensors exhibited a very low limit of detection of 50–100 ppb for volatile organic compounds (VOCs) at room temperature. In addition, the NR/MXene sensor allows detection of the mixture of ammonia (NH3), dimethyl sulfoxide (DMSO), and acetone (C3H6O) and it shows good response depending on the total concentration of VOC gases. Furthermore, the flexible nanocomposite sensor exhibits stable sensing performance at different bending states (0‐120°) and shows 20‐day atmospheric stability. This sensor's ability extends to alcohol breath analysis, useful for drunk driving detection. This work paves the way to the possibility of using robust MXene‐based toward practical realization of electronic devices.

Crack tip stress intensification in strain-induced crystallized elastomer

Natural rubber (NR) exhibits strain-induced crystallization (SIC), enhancing tearing strength and crack resistance. However, the reinforcement mechanism along with nonuniform strain around a crack tip remains unclear. We reveal the nonuniform stress field around a crack tip using the DIC-based deformation field data and a hyperelasticity approach. A hyperelastic strain energy density function (W) is derived to be able to replicate stress-strain data across various deformations, encompassing equal and unequal biaxial, uniaxial, and pure shear stretching. These data cover the full range and magnitude of deformations around the crack tip. SIC significantly impacts the singular behaviors of strain and stress near the crack tip, causing a pronounced stress increase and strain decrease within the SIC zone that extends up to approximately 100 μm away from the crack tip. This results in a distinct crossover in singularity power-law index between the SIC zone and the fully amorphous zone. With increasing crack opening, the stress upturn intensifies, and the crossover shifts away from the crack tip due to SIC zone enlargement and local crystallinity increase. These findings deepen our understanding of the physics of SIC near crack tips and its reinforcement mechanism in strain-induced crystallizable soft solid materials.

Analyzing the Reinforcement of Multiwalled Carbon Nanotubes in Vulcanized Natural Rubber Nanocomposites Using the Lorenz–Park Method

In this study, multiwalled carbon nanotubes (MWCNTs) were incorporated into vulcanized natural rubber (VNR) matrixes to create nanocomposites with improved mechanical, thermal, and electrical properties. The interfacial interaction of the MWCNTs with the VNR matrix was quantitatively evaluated based on the crosslink density value calculated using the Flory–Rehner methodology. Various rheometric parameters were influenced by the addition of the MWCNTs, including minimum torque (ML), maximum torque (MH), and scorch time (tS1). The MWCNTs significantly enhanced the vulcanization of the composites based on the VNR matrix. This study highlights the impact of MWCNTs on crosslink density, improving mechanical properties and reducing swelling in the VNR matrix. We discovered that the MWCNTs and the VNR matrix interact strongly, which improved the mechanical properties of the matrix. The MWCNTs improved the hardness, tensile strength, and abrasion resistance of the VNR/MWCNT nanocomposites. Based on dynamic mechanical analysis, MWCNT incorporation improved stiffness as indicated by a change in storage modulus and glass transition temperatures. The addition of MWCNTs to the VNR/MWCNT nanocomposites significantly improved their electrical properties, reaching a percolation threshold where conductive pathways were formed, enhancing their overall conductivity. Overall, this study demonstrates the versatility and functionality of VNR/MWCNT nanocomposites for a variety of applications, including sensors, electromagnetic shielding, and antistatic blankets.

Genome-Wide Identification of the Geranylgeranyl Pyrophosphate Synthase (GGPS) Gene Family Associated with Natural Rubber Synthesis in Taraxacum kok-saghyz L. Rodin.

Taraxacum kok-saghyz Rodin (TKS) is a recognized alternative source of natural rubber comparable to the rubber tree. The geranylgeranyl pyrophosphate synthase (GGPS) catalyzed the synthesis of geranylgeranyl pyrophosphate (GGPP), which is an important enzyme in the secondary metabolism pathway. In this study, we present the first analysis of the GGPS gene family in TKS, where a total of seven TkGGPS family members were identified. Their core motifs, conserved structural domains, gene structures, and cis-acting elements were described. In addition, two phylogenetic trees were constructed based on the Neighbor-Joining and Maximum-Likelihood methods, and the TkGGPSs were highly conserved and exhibited good collinearity with the other species. Transcriptome data showed that seven TkGGPS gene members were expressed in all the 12 tissues measured, and TkGGPS1, TkGGPS3, and TkGGPS6 were highly expressed in latex, suggesting that they may be associated with natural rubber synthesis. Meanwhile, quantitative real-time PCR (qRT-PCR) showed that the expression levels of the TkGGPS genes were regulated by the ethylene and methyl jasmonate (MeJA) pathways. Subcellular localization results indicated that all the TkGGPS proteins were also located in chloroplasts involved in photosynthesis in plants. This study will provide valuable insights into the selection of candidate genes for molecular breeding and natural rubber biosynthesis in TKS.

Strategies for identification of elite Hevea brasiliensis genotypes tolerant to ALF disease from half-sib and full-sib population

Natural Rubber (NR) from Hevea brasiliensis tree is an important commercial commodity worldwide. In general, many Hevea cultivars are vulnerable to abnormal leaf fall (ALF) disease caused by Phytophthora spp., which can lead to considerable reduction in crop production. Chemical control of ALF by spraying mineral oil-based copper fungicides is the conventional approach which is harmful to the ecosystem. Development of ALF tolerant varieties of Hevea through conventional breeding is the major objectives of this study. We evaluated the primary agronomy traits and ALF tolerance level of the newly developed Hevea clones using in vitro leaf disc bioassay as well as field screening for disease incidence consecutively for three years. Variation in disease infestation was observed among genotypes. Based on field screening, the clones which showed better field tolerance against ALF than the parental clones were selected. Clone 683 was identified as one of the most desirable genotypes which had vigorous growth as well as high crop yield in addition to ALF tolerance. The study also confirms the reliability of in vitro leaf disc bioassay technique for screening against ALF across genotypes for its inherent variability. This technique is rapid and easier and can be completed within 96 hours. This approach could reduce the burden of screening larger breeding population to a manageable size to enhance the efficiency of selection in ALF disease resistance breeding programs. Selected fast growing, high yielding ALF tolerant clones, could be further evaluated in on farm trials for recommending to the growers in the traditional region of rubber growing tracts.

Fitness club adjacent to a quiet corporate office - Prototypes

There is a demand for fitness clubs in hotels, residential, and corporate buildings - sometimes adjacent to sensitive spaces. Activities involving weight drops and spinning bikes, among others, cause dynamic forces in the structure that propagate through the building's structure and radiate airborne sound. There is an effort by acousticians worldwide to establish a standardized method for measuring and rating the noise radiated by gyms into adjacent areas. This article describes the construction of a gym over a corporate office, occupying an area of 2100 m2 each. The gym's floor structure is a concrete and steel deck, and the office below has low sound levels. The goal of making gym activity inaudible in the office is undoable in practice. We tested several prototypes to arrive at a double insulation system with a floating slab with natural rubber mounts. A system of dynamic dampers was installed to reduce the movement of the floating slab with the dynamic excitation above it. The results of the prototype were auspicious. This paper presents the measurements of the natural frequency of the structure and the floating slab, the transmissibility of the system, and the differences in vibratory velocity from the floating floor to the structure.

Experimental and Numerical Evaluation of the Stress-strain Characteristic for Synthetic Rubber Spheres

Experimental and Numerical Evaluation of the Stress-strain Characteristic for Synthetic Rubber Spheres

Production of eco composites based on natural rubber and recycled sugarcane bagasse waste to be utilised as a type of food contact

Natural fibres are abundant, renewable, and biodegradable, which has inspired numerous academics worldwide to investigate their possible applications in various industrial fields. The food packaging sector is seeking bio-based and biodegradable substitutes to increase sustainability. In this study, new composites were prepared from natural rubber (NR) and sugarcane bagasse fibres (SCB) with different concentrations of SCB (0, 2.5, 5, 10 &20 phr). The effect of SCB on the properties of natural rubber was studied before and after the alkaline treatment of the fibres. The biocomposites are characterized using Fourier transmission infrared spectroscopy, thermogravimetric analysis, scanning electron microscope, transmission electron microscope, and dielectric measurements in addition to rheological and mechanical analysis. The overall migration test for biocomposites loaded with 20phr SCB was performed to assess the biocomposite’s safety as food contact materials. The study’s results indicated that, adding SCB improved the conductivity, tensile strength, and elongation at break of natural rubber. Alkaline treatment strengthened the bonding between the filler and matrix and improved biocomposites’ thermal dielectric and mechanical properties. The overall migration test indicated that the alkaline treatment increased the overall migration to simulants. Accordingly, alkaline-treated NR-SCB biocomposites are effective eco-friendly food packaging candidates for certain types of food such as aqueous non-acidic products.

Raw rubber network of acid-free natural rubber and its application with solution-polymerized styrene butadiene rubber in green tires

Natural raw rubber was prepared by flash evaporation process (VNR), its raw rubber network was compared with that of acid-coagulated rubber (STR20), and the effects of the ratios of VNR and STR20 to SSBR on the comprehensive performance of green tire composites were investigated. The results showed that compared with 80SSBR composites, the tensile strength and tensile product coefficient of 80VNR composites were improved by 23 % and 94 %, and the Payne effect, compression heat generation, and rolling resistance were reduced by 39 %, 9 %, and 5 %, respectively. Compared with 40STR20/40SSBR composites, the tensile product coefficient, wear resistance, and wet skid resistance of 40VNR/40SSBR composites are increased by 11 %, 5 %, and 5 %, respectively, and the Payne effect, compression heat generation, and rolling resistance were reduced by 46 %, 11 %, and 5 %, respectively. This study increased the amount of natural rubber in the green tire formulations, improving the performance of composites while achieving sustainability.

Advanced and sustainable EMI shielding composites: Natural rubber-nitrile rubber blends enhanced with hydrothermally synthesized Polyaniline Nanofibers and spinel strontium ferrites

Conductive fillers, such as metals and carbon compounds, often exhibit lower compatibility with polymer matrices, leading to agglomeration phenomena that negatively impact the processing and performance of composites. Polyaniline (PANI) nanofibers, with their high conductivity, rapidly create conductive pathways upon contact, reducing current leakage and dielectric loss in composites. To address the compatibility challenges between fillers and matrices, this study adopts a simple, cost-effective approach for synthesizing highly efficient EMI shielding composites. Specifically, we employ hydrothermal synthesis to enhance the properties of PANI nanofibers and spinel strontium ferrites, significantly improving their performance as filler particles. By modifying the morphology of the conductive fillers and incorporating magnetic particles wrapped with an insulating polymer layer, we enhance filler-matrix compatibility. Notably, the synthesized system is a composite made of natural rubber, highlighting its relevance and importance in the current era. This approach not only improves compatibility but also leverages the sustainable properties of natural rubber, making it a significant advancement in the field of EMI shielding materials. In this paper, we report a flexible EMI shielding composite with efficient EM wave absorption, prepared using a natural rubber-nitrile rubber blend as the matrix, and hydrothermally synthesized improves polyaniline nanofibers and spinel strontium ferrite as functional fillers. The shielding efficiency (SET) increases up to 36 dB with different PANI-SrFe2O4wt percentages. This demonstrates the potential of composite for high-performance applications.

The Nano-Revolution in Rubber Bushings: Boosting Mechanical Performance

Abstract A new method for manufacturing rubber bushings with unique properties has been introduced. The method involves adding alumina nanoparticles at different ratios (0.2, 0.4, 0.6, 1, 1.5, 2, 2.5, and 3) Phr to a rubber recipe consisting of 30% natural rubber, 70% styrene-butadiene rubber. The recipe also contains a constant percentage of carbon black (51 Phr). The materials were mixed for (specific time) to ensure even distribution. Extensive testing has been conducted to ensure the cured rubber meets performance standards, including evaluations of tensile strength, tear propagation, wear resistance, hardness, elasticity, and resistance to fatigue. The bush material excelled in friction resistance and long-term fatigue performance. Adding 0.6 phr Nano-Alumina further enhanced its elasticity, strength, tear resistance, and resilience. At 3 phr of Al2O3 increased Elongation, Hardness, and Fatigue resistance value.

The influence of myrcene on anionic copolymerization of 1,3-pentadiene and styrene

C5-dienes including 1,3-pentadiene (PD) and isoprene (IP) as by-products of naphtha cracking are important industrial raw materials for the production of thermoplastic elastomers, synthetic rubber and resins. The research on living anionic polymerization (LAP) of myrcene (MY) is also of great significance for the development of new bio-based materials and products. Focusing on the optimal utilization of C5 resources and the high-value utilization of biomass resources and the realization of green chemical production, this article reports the synthesizing of a novel terpolymer by LAP of PD, styrene (ST) and the biomass monomer MY. The discovery of the alternating sequence structure of ST and PD inspires us to further explore the development of copolymers containing this unique sequence structure. The special long branched side chain of MY and its low glass transition temperature are also conducive to the synthesis of new integrated rubbers. The 1H NMR tracking analysis indicates that the polymerization pattern changes from alternating sequence to gradient block sequence with the increase of MY content. Combined with FTIR analysis, the PD monomeric units are mainly trans-1,4 structure and MY monomeric units are predominant cis-1,4 structure. Considering the extremely high polymerization activity of MY compared to ST and PD, the copolymerization rate is significantly dependent on the concentration of the PD monomer. Despite this, due to the interactions between ST and PD ([ST¦PD] intermediate), ST still tends to form alternating segments with PD. The ternary copolymerization can be viewed as a “binary gradient copolymerization” of [ST¦PD] and MY (rMY > r[ST¦PD]).

Synergic effects of physio‐mechanical performances on sliding‐rolling tribological and abrasion behaviors of polyisoprene based aviation tire treads

AbstractAbrasion and tribological properties of tread rubber play a crucial role in governing the service life of aviation tires and the safety of aircrafts. Polyisoprene (IR) with the same chemical structure as natural rubber shows great potential for application in aviation tires. Herein, the abrasion and tribological behaviors of IR based composites under sliding‐rolling conditions were investigated in relation to the carbon black (CB N234) content, sliding‐rolling ratio, ambient temperature, and counterparts in order to provide guidance for the development of high‐performance aviation tire treads. Moreover, the relationship between wear performances and physical–mechanical properties was discussed to establish a prediction model. The results revealed that physical and mechanical properties affected wear performances in a synergetic manner, which could be described as a negative linear correlation of the folding wear with the product of hardness and rebound resilience (H4R) and the ratio between rebound resilience and tensile strength ((1‐R)/σ) even at elevated temperature and sliding‐rolling ratio regardless of the counterpart. The increase in CB N234 content and sliding‐rolling (s‐r) ratio resulted in a transition of the wear mechanism from folding to abrasion due to the formation of soft rubber particles with a certain fluidity and a lubricating transfer film that was located at the friction interface and was generated by the thermal‐mechanical degradation of the IR matrix when it was rubbed against steel counterparts, which marred the aforementioned negative linear relationship.Highlights The increase in temperature improved the abrasion resistance of tire treads. The folding wear was negatively and linearly related to H4R and (1‐R)/σ. Increasing CB N234 content and s‐r ratio made a transition of wear mechanism.