Rubber Composites Research Articles

Coffee grounds as sustainable filler for bio‐based rubber composites

AbstractUsing biological/renewable resources as filler or modifier in both thermoplastics and rubbers has been of a great interest in order to reduce negative effects of traditional petroleum/natural gas based fillers. In this study, the main goal was the use of spent (waste) coffee grounds as a natural alternative filler to carbon black in acrylonitrile butadiene rubber (NBR) based compounds. Carbon black (CB) was partially replaced with fresh as well as spent coffee grounds (SCG) in NBR compound formulation. Stabilization effect of fresh coffee grounds was also investigated. Cure characteristics, physico‐mechanical, thermal, morphological, and dielectric properties of the bio‐based composites were tested and compared with the control (reference) compounds. Processability has been affected positively in the case of using coffee grounds thanks to the presence of triacyl groups in coffee. Up to 20% higher elongation at break values were measured when coffee is partially replaced with CB. Abrasion loss and oil resistance could be retained for coffee containing compounds. In conclusion, SCG were found to be a good natural alternative filler for bio‐based NBR composites without a significant change in material properties.Highlights Spent coffee grounds ‐ a sustainable filler in bio‐based NBR composites Both fresh and spent coffee grounds are successful stabilizers Physico‐mechanical, thermal, and dielectric properties are comparable

FORMATION OF CHROMATED COATINGS ON A PRESS TOOLING IN THE PRODUCTION OF RUBBER PRODUCTS FOR ROCKET AND SPACE TECHNOLOGY

This research analyzes the influence of residual stresses formed as a result of the process of self-propagating high-temperature synthesis on the mechanical properties and durability of structural materials and protective coatings. The main emphasis is placed on the analysis of the relationship between residual stresses and adhesive strength and durability of the obtained coatings. Rubber-based composites may prove to be competitive and eventually replace traditional materials in a number of applications, as there are many advantages to using these materials. For example, rubber-based composites often have a lower density than traditional materials such as metals. This leads to a reduction in the weight of products, which is important in a variety of industries where lightness is a key characteristic. Rubber composites are characterized by cushioning, flexibility, and elasticity, which makes them able to handle dynamic loads and adapt to various forms of deformation without losing structural properties. Research was carried out on parts of press tooling used for manufacturing of rubber-technical products in rocket-space engineering. It was found that residual stresses formed during the SHS process have a significant effect on the adhesion properties of protective coatings. Residual stresses appear after SHS treatment under conditions of thermal self-ignition of SHS charges. At the cooling stage of the SHS process, residual compressive stresses appear as a result of the elastic interaction of the alloyed titanium coating and the structural material, which have different sizes and coefficients of thermal expansion. The maximum values of adhesion strength of titanium coatings on steel 45 were 120-150 MPa when alloyed with aluminum and 180-210 MPa when alloyed with chromium. This research emphasizes the importance of residual stress control for improving the strength and durability of protective coatings obtained under SHS conditions and their possible role in extending the service life of structures and equipment. Additional research in this direction may contribute to process optimization and product quality improvement in the aerospace industry.

Enhancement of the Electric-Force Response of Carbon Black/Silicone Rubber Composites by Silane Coupling Agents.

Flexible strain sensors have a wide range of applications in the field of health monitoring of seismic isolation bearings. However, the nonmonotonic response with shoulder peaks limits their application in practical engineering. Here we eliminate the shoulder peak phenomenon during the resistive-strain response by adjusting the dispersion of conductive nanofillers. In this paper, carbon black (CB)/methyl vinyl silicone rubber (VMQ) composites were modified by adding a silane coupling agent (KH550). The results show that the addition of KH550 eliminates the shoulder peak phenomenon in the resistive response signal of the composites. The reason for the disappearance of the shoulder peak phenomenon was explained, and at the same time, the mechanical properties of the composites were enhanced, the percolation threshold was reduced, and they had excellent strain-sensing properties. It also exhibited excellent stability and repeatability during 18,000 cycles of loading-unloading. The resistance-strain response mechanism was explained by the tunneling effect theoretical model analysis. It was shown that the sensor has a promising application in the health monitoring of seismic isolation bearings.

Shock attenuation of silicone rubber composites with shear thickening fluid

This study investigated the enhancement of shock attenuation in silicone rubber (SR) matrix composites through the incorporation of shear thickening fluid (STF) microdroplets. A series of SR-STF composites with various STF mass fractions (0 to 50 wt. %) were fabricated using an efficient emulsification method. The primary focus was on assessing the shock attenuation capabilities of SR-STF through laser-induced shock experiments. The results indicate a significant improvement in shock wave attenuation in the composites due to the addition of STF microdroplets. Notably, the SR-STF composite containing 30 wt. % STF exhibited a maximum 60 % reduction in shock pressure attenuation compared to SR of the same thickness. This enhancement is attributed to multiple mechanisms, including viscosity-induced dissipation, the initiation and propagation of cracks within both the SR matrix and the STF microdroplets, and interface-induced effects like interface separation, shock wave reflection and scattering, along with the thickening behavior of STF. An intriguing observation was the interplay of these mechanisms at different STF concentrations, leading to the identification of an optimal STF content for maximizing the shock attenuation. This research's findings highlight the crucial role of STF microdroplets in shock wave attenuation and offer a strategic approach for developing SR matrix composites with enhanced shock attenuation capacities.

Quantification of tire wear particles in road dust based on synthetic/natural rubber ratio using pyrolysis-gas chromatography–mass spectrometry across diverse tire types

Increase in road traffic leads to increased concentrations of tire-wear particles (TWPs), a prominent source of microplastics from vehicles, in road dust. These particles can re-enter the atmosphere or move into aquatic ecosystems via runoff, impacting the environment. Consequently, accurately assessing and managing TWP levels in road dust is crucial. However, the ISO method (ISO/TS 20593 and 21396) uses a constant ratio of styrene-butadiene rubber (SBR) to natural rubber (NR) for all tires, disregarding the variability in tire composition across different types and brands. Our study found substantial SBR content (15.7 %) in heavyweight truck tires, traditionally believed to be predominantly NR. We evaluated the SBR/NR content in 15 tire types and proposed a method to more accurately evaluate TWP concentrations in road dust from five different locations. Our findings suggest that the conventional ISO method may underestimate the concentrations of TWP due to its reliance on a static ratio of SBR/NR. This study underscores the necessity for a more flexible approach that can adapt to the variability in SBR and NR content across different tire types. By delineating the limitations inherent in current assessment methods, our research contributes to a more adaptable understanding of TWP concentrations in road dust. This advancement prompts the development of a revised methodology that more accurately reflects the diverse compositions of tire rubber in environmental samples.

Application of nano-insoles on functional recovery in early postoperative period in intertrochanteric femur fractures

This study investigates the effect of integrating family empowerment programs with the application of nanoinsoles on functional recovery in the early postoperative period in elderly patients with intertrochanteric femur fractures (IFF). A total of 100 elderly patients with IFF, who underwent internal fixation and were admitted to our hospital from November 2020 to October 2021, were selected and divided into an observation group (n = 50) and a control group (n = 50). The control group mainly received perioperative routine health-care education. The observation group received a family empowerment program and used nano-insoles prepared by carbon nanotube/silicone rubber composites during the perioperative period and before discharge. After postoperative follow-up, the care readiness of the main caregivers and hospitalization time were compared in the two groups. The scores of activities of daily living (ADL), Harris Hip Function Scale (HHS), Hospital Anxiety and Depression Scale (HADS), quality of life, satisfaction with care, and complications were recorded. The results demonstrated that the observation group exhibited significantly higher care readiness, nursing satisfaction rates, HHS, and ADL scores, as well as reduced hospitalization time and HADS scores compared to the control group. After 3 months post-surgery, the quality of life in the observation group was significantly superior to that of the control group. The incidence of complications in the observation group (8%) was significantly lower than that in the control group (24%). In conclusion, the family empowerment programs combined with the application of nano-insoles on patients with IFF can effectively improve postoperative functional recovery.

Novel antioxidants based on polymerized 2,2,4-trimethyl-1,2-dihydroquinoline for styrene-butadiene rubber composites

Novel antioxidants based on polymerized 2,2,4-trimethyl-1,2-dihydroquinoline for styrene-butadiene rubber composites

Effects of High-Energy Electron Beam-Modified Fumed Silica on the Structure and Properties of Silicone Rubber Composites

Effects of High-Energy Electron Beam-Modified Fumed Silica on the Structure and Properties of Silicone Rubber Composites

Effect of Titanium Dioxide on Cure Characteristics and Physico Mechanical Properties of High-Temperature Vulcanizing Silicone Rubber Composites

Silicone rubber (SiR), a vital elastomer, is extensively used in producing various engineering and general products, owing to its distinctive properties. Despite the remarkable properties, SiR-based products require anti-microbial agents such as titanium dioxide, TiO2 to negate black mold issues. Still, adding this agent alters the composites' processability and physical and mechanical properties. This study examined the impact of adding different TiO2 content as fillers on silicone rubber composites' processability, physical properties, and mechanical properties. Raw materials of 20-hardness high-temperature-vulcanization (HTV) SiR- reinforced with various TiO2 contents at 0.0, 0.3, 0.6 and 1.2 wt% were prepared using a two-roll mill. The results indicated SiR composites reinforced with 0.3 wt% TiO2 exhibited the best performance with a tensile strength of 1.49 MPa, elongation at break of 340.87%, modulus 100% of 0.664 MPa, modulus 300% of 0.822 MPa, and modulus 500% of 0.954 MPa. This performance can be attributed to the efficient crosslink density and the effective interactions between the TiO2 and silicone rubber particles at this concentration. Structural and morphological analyses further corroborated the results. Consequently, it can be inferred that silicone rubber reinforced with 0.3 wt% titanium dioxide holds the potential for formulating silicone rubber compounds that necessitate anti-microbial properties.

Structural, radiation shielding, thermal and dynamic mechanical analysis for waste rubber/EPDM rubber composite loaded with Fe2O3 for green environment

Increasing waste rubber recycling produces a specious range of products for many valuable applications. Waste Rubber/EPDM composite with different concentrations was prepared. Infrared spectroscopy (FTIR) is used to identify the chemical composition. A water absorption test, Dynamic mechanical analysis (DMA), and Thermal Gravimetric Analysis (TGA) were performed. The (75/25) WR/EPDM rubber composite exhibited the best behavior with the highest mechanical performance. Fe2O3 was added to (75/25) WR/EPDM rubber composite. Water absorption, FTIR, TGA, and DMA were investigated. The composite performance was improved with increasing Fe2O3 content. The linear attenuation coefficients (μ) were also measured as a function of the concentrations of Fe2O3 for γ-ray energy 662 keV by using 137Cs point source; the radiation shielding can be denoted by numbers of parameters like mass attenuation coefficient (μm), half value layer (HVL), Tenth value layer TVL and radiation protection efficiency (RPE%), radiation protection efficiency increased as Fe2O3 increased.

Effects of boron nitride nanoplates on the dielectric and mechanical properties of carbon nanotubes/silicone rubber composites

AbstractCarbon nanotubes (CNTs) have aroused great attentions in silicone rubber (SR) composites due to the excellent electrical and mechanical properties. However, the distribution of CNTs is not ideal because of the agglomeration effect of nanomaterials. Incorporating different dimensional nanofillers may be a solution. In this work, two‐dimensional boron nitride (BN) was added to fabricate CNTs/BN/SR composites. The results showed that BN could benefit the dispersion of CNTs and improve the dielectric and mechanical behaviors of the composites. Large dielectric constant (5.35, 92% more than pure SR) with extremely low loss tangent (0.00108) was obtained in the SR composites incorporated with 2 wt% CNTs and 5 wt% BN. High tensile stress (836 kPa) and elongation at break (332%) were also achieved, with a low elastic modulus of 557 kPa. Besides, the CNTs/BN/SR composites had thermal stability up to 400°C. Thus, enhanced dielectric and mechanical properties were achieved in CNTs/BN/SR composites by incorporating different dimensional nanofillers, which have great potential applications in dielectric elastomer composites.

Natural rubber composites reinforced with sodium sulfate waste from pigment industry: A circular economy approach for solid waste management

The massive industrial waste discharged into the environment adversely affects the ecological system. Traditional methods like landfilling or other disposal methods can no longer be adequate to handle them, and their reutilization is consequently gaining popularity. Most chemical industries generate a large amount of sodium sulfate waste (SSW), contaminating air and water. Hence, its reutilization in natural rubber (NR) as a reinforcing filler is explored. SSW generated in Ultramarine and Pigments Ltd., Chennai, India, was procured and characterized. The fabricated NR-SSW composite's cure, mechanical, and sorption features have been investigated. NR composite with 7.5 phr (parts per hundred of rubber) SSW showed a 9 %, 14 % and 29 % increase in tensile strength, tear strength, and modulus at 300 % elongation, respectively, and a remarkable decrease in abrasion loss and higher abrasion resistance index (ARI) as compared to NR-Neat. All these properties decreased beyond 7.5 phr SSW addition, proving its better adhesion on NR up to 7.5 phr loading. The experimental tensile strength showed a good correlation with Turcsányi-Pukànszky-Tüdõs (T-P-T) model, confirming the better matrix-filler interaction up to 7.5 phr SSW loading. Sorption studies proved the better barrier properties of NR-SSW7.5 composite compared to NR-Neat. Various kinetic parameters were studied, and a suitable transportation method was suggested. NR-SSW7.5 composite, having remarkable mechanical and barrier properties, finds application in various rubber products manufacture. The reutilization of SSW as an efficient filler in NR is an innovative attempt from a circular economy perspective, as it reduces production costs and environmental pollution.

Experimental investigation on the mechanical properties of cement mortar containing recycled tire crumbs reinforced with polypropylene, oil palm and banana fibers

The automotive industry discards a large number of end-of-life tires annually, creating a growing global environmental hazard. The incorporation of crumb rubber derived from waste tires into construction materials is considered one of several alternatives for sustainably reusing these waste materials. The addition of fibers as reinforcements would address the typical degradation caused by the crumb rubber in cement composites. Fibers sourced from plants and recycled synthetics offer a practical and eco-friendly reinforcement material that is both cost-effective and easy to procure. However, two challenges emerge from these choices. Firstly, natural fibers exhibit substantial regional variations, resulting in differences in their properties and inconsistent performance. Secondly, recycled materials also demonstrate variation due to disparities in production and manufacturing processes. As a result, incorporating these fibers into cement-based materials has produced conflicting outcomes due to these inherent variations, rendering practical application unfavorable. Therefore, this study attempts to promote the adoption of sustainable practices by addressing the lack of available performance-based data for the utilization of these fiber variants in the design of cement mixtures. The data would allow engineers to integrate these mixtures into commercial designs for practical in-situ construction. A total of 18 novel cement-based mixtures containing different types of fibers, chemical admixture, and discarded crumb waste were formulated and evaluated in fresh and hardened properties. A multifaceted approach was also undertaken to further hybridize the fibers and quantify the synergistic effects within the investigated cement matrice. The results indicate that the incorporation of polypropylene and oil palm fibers enhances compressive and tensile strength, although there is a general weakening observed in flexural strength. In the case of hybrid fibers, a successful combination of polypropylene and banana fibers is evident, showing a positive hybrid effect coefficient compared to a negative coefficient for polypropylene-oil palm fiber combinations.

A Low-Cost Soft Gripper for Automated Pick-and-Place Systems

The study introduces a pioneering low-cost soft gripper designed for the automation industry, specifically targeting sensitive handling requirements in the food and health sectors. Utilizing rubber or elastic composites, the gripper combines improved sensitivity and adaptability to handle delicate materials safely and efficiently, aligning with stringent industry standards. Central to the design is a pneumatic control system that ensures precise manipulation, allowing the gripper to adapt to varying object contours without causing damage. This innovation not only addresses the mechanical aspects of soft robotics but also integrates seamlessly with Industry 4.0 technologies through smart sensors and AI algorithms, enhancing operational intelligence and versatility. By leveraging additive manufacturing techniques, the design also achieves significant cost reductions, facilitating broader adoption. This study's soft gripper represents a critical step forward in the development of robotic systems that can perform complex tasks with high sensitivity and economic efficiency, promising transformative impacts on the automation capabilities of sensitive industrial sectors.

Cure characteristics and mechanical properties of natural rubber vulcanizates filled with untreated pyrolytic tire char

AbstractUntreated pyrolytic tire char was used in natural rubber (STR20) composites as single filler at loadings of 30–70 phr and co‐filler with carbon black (N330) at a total loading of 50 phr. The results were compared with rubbers filled with N330 and crumb rubber at 30 phr. The effects of fillers on cure characteristic, crosslink density, filler dispersion in natural rubber vulcanizates and their mechanical properties were investigated. The slight reversions were seen for the cure characteristics of 70 phr‐char‐filled and all co‐filler samples because the sulfur amount in the char together with the added sulfur could shift the vulcanization system from EV to SEV, whereas plateau cure curves were seen for the rest. While the highest tensile strength of char‐filled sample was obtained at 50 phr loading, whose tensile strength was about 88% of the N330 sample at 30 phr, 70‐phr‐char filled sample was superior in surface hardness, abrasion resistance and tear strength to N330 sample at 30 phr. For rubber with co‐fillers, the mechanical properties depended on the mass ratio of N330 to pyrolytic tire char. Therefore, it is possible to use untreated char as reinforcing filler for suitable applications according to their properties.

Improving the mechanical and abrasion properties of silica-reinforced styrene-butadiene rubber composites by optimizing the concentrations of compatibilizers

Silica (chemical formula SiO2) is a promising, more environmentally friendly alternative to carbon black (CB) used in the rubber industry as a filler. Although silica is already used in rubber products, it is not used as extensively as CB because the polar surface of silica cannot interact well with the apolar polymer molecules of the most frequently used rubbers. To solve this problem, experts have tried different grafting methods and several coupling agents for a stronger silica-elastomer connection. In this article, we used bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) and polyethylene glycol (PEG) combined to improve the connection between the surface of silica and the apolar styrene-butadiene rubber (SBR) matrix. We examined mechanical and structural properties and found that adding 3 phr PEG and 4.5 phr TESPT to SBR is optimal for 60 phr silica content. This ratio of additives resulted in a 48% improvement in tensile strength. The positive effect of the coupling agents shows up in abrasion mass loss and tear strength as well.

An Experimental Study of the Properties of Carbon Fiber/Epoxy Composites Mixed with Rubber Granules

In this research work, the mechanical properties of hybrid composites reinforced with woven carbon fiber mats particulated with natural rubber powders as fillers in the epoxy resin matrix were investigated. The specimens were prepared by the hand-layup process followed by a vacuum bag moulding process. The vacuum moulding reduces the voids or cavities in the hybrid composites. The natural rubber powder was added in different weight proportions (5%, 10%, 15%, and 20%), and carbon fiber is added in 20% for all the specimens. Experiments such as tension testing, flexural testing, water absorption/acid corrosion/base corrosion tests, dynamic mechanical analysis (DMA), and scanning electron microscopic (SEM) analysis were conducted to evaluate the epoxy carbon rubber (ECR) composites. The tensile and flexural test findings demonstrated that the addition of 10% natural rubber particles gave better results as compared with other proportions. The water/acid/base absorption test findings reveal that the ECR composites are not affected by water/acid/base. The DMA teat findings show that ECR composites having 10% natural rubber have higher damping factor, storage, and loss modulus. The SEM analysis shows that ECR hybrid composites with 10% rubber particles contained a uniform distribution of rubber particles over reinforcement, and also, there were no cracks and voids. According to this research findings, ECR hybrid composites with 10% natural rubber particles prepared during the vacuum bag moulding process can be used to prepare aerospace interior components.

Preparation of low‐rolling resistance natural rubber composites from pyrolysis carbon black by plasma treatment

AbstractIn this study, the surface of pyrolysis carbon black (CBp) is modified by integrating the ball milling process with plasma treatment. High‐energy mechanical ball milling enabled more uniform contact and sufficient reaction temperature for the silane coupling agent and CBp. In addition, the impact of plasma activated the ash and surface deposits of CBp, reducing its inertness. Herein, the filler dispersion grade, Payne effect, vulcanization characteristics, and mechanical and dynamic mechanical properties are investigated by considering modified CBp/natural rubber (NR) composites. The ball milling plasma process can reduce the polarity of CBp. Compared with untreated CBp/NR composites, the plasma‐treated SCA‐CBp/NR composites exhibited increased CBp dispersion grades, higher processing safety, better processing fluidity, and improved mechanical properties. The reduced Payne effect ensured more filler‐rubber network structure, resulting in a reduction in rolling resistance.HighlightsThe coupling agent and CBp are treated by low‐temperature plasma and ball milling.The process promotes the formation of the filler‐rubber network.The dispersion grade of composites increased by 26.29%.The tensile strength increased by 5.57%, and the rolling resistance decreased by 19.44%.

Mitigation of zinc and organic carbon leached from end-of-life tire rubber in cementitious composites

End-of-life tire (ELT) rubber has been widely researched to replace fine or coarse aggregates in cementitious composites. While most studies paid attention to its effect on the engineering properties, very few considered chemical reactions with pore solution and the potential for environmental leachate. Recently the authors developed a methodology to remove zinc from the ELT rubber, since zinc can be toxic if it is leached into the environment. In this study, the authors utilized ELT rubber before and after the zinc extraction process to partially replace fine aggregate in a mortar. Flowability, compressive strength, flexural strength, and ultrasonic pulse velocity were measured for the engineering properties of rubberized mortars. Simultaneously, isothermal calorimetry was also employed to investigate the effects of ELT rubber on the hydration process of the rubberized mortars. In addition, the pore solution and leaching solutions were taken at different curing ages and then analyzed for elemental and total organic carbon (TOC) contents. The results showed a remarkable loss in engineering properties of rubberized mortar when ELT rubber was utilized, and the decrease in performance was more pronounced in the samples with zinc-extracted ELT rubber. The pore solution was found to contain significant quantities of zinc and TOC. However, the authors also found that using silica fume to partially replace cement could effectively recover the loss in strength and could reduce the leachability of zinc and TOC.

Enhancing gamma radiation shielding properties of iron metal and natural rubber composites

AbstractA comparative study was conducted to investigate the gamma and neutron radiation shielding properties of composites made from iron metal (micro and nano) dispersed within natural rubber (NR). The aim was to attenuate neutron and γ‐rays. The study utilized the gamma spectroscopy technique and the Monte Carlo FLUKA code. To assess the gamma ray shielding, a 3×3 Nal (Tl) detector and radioactive point sources were employed. Two comparative studies were carried out, one using Fe loaded NR (Fe/NR) composites in microsize and the other using Fe/NR composites in nanosize. The objective was to determine the impact of iron nanoparticles on the shielding ability of the composites. The findings revealed that the Fe/NR composites in nanosize exhibited superior gamma radiation shielding ability compared with the Fe/NR composites in microsize. These results were supported by the FLUKA Monte Carlo code, which demonstrated good agreement with both the experimental and theoretical XCOM data.