Properties Of Rubber Research Articles

Modulation of Mechanical Properties of Silica-Filled Silicone Rubber by Cross-Linked Network Structure.

Associating molecular structure and mechanical properties is important for silicone rubber design. Although silicone rubbers are widely used due to their odourless, non-toxic, and high- and low-temperature resistance advantages, their application and development are still limited by their poor mechanical properties. The mechanical properties of silicone rubbers can be regulated by designing the cross-link density and cross-linking structure, and altering the molar contents of vinyl in the side groups of methyl vinyl silicone rubber (MVQ) leads to different cross-linking structures and cross-linking densities in the vulcanized rubber. Therefore, this study investigated the differences in molecular parameters and molecular chain structures of unprocessed MVQ rubbers with different vinyl contents. The results showed that MVQ rubbers with high vinyl contents were branched polymers, better facilitating the cross-linking reaction than MVQ rubbers with low vinyl contents. In addition, silicone rubbers with different vinyl contents were co-cross-linked to introduce an inhomogeneous cross-linked network in the silicone rubber to improve its mechanical properties. The cross-linked network properties were analysed by the Flory-Rehner model and Mooney-Rivlin plots, and it was found that the long chains in the sparsely cross-linked domains of the network favoured high elongation at break and the short chains in the densely cross-linked domains contributed to high modulus, which could satisfy the functions of reinforcing and toughening the rubber materials at the same time. It was also found by analysing the filler network and aggregate morphology that the inhomogeneous cross-linked network led to an improvement in the dispersion of silica in the rubber and a significant improvement in the mechanical properties of silicone rubber.

Utilization of spent bleaching earth as green filler and plasticizer in the manufacture of rubber compounds for solid tire production

This study utilized spent bleaching earth (SBE) as a single form of filler and plasticizer in the manufacture of rubber components for solid tire vulcanizate. SBE, an underutilized byproduct of vegetable oil purification, is abundantly available globally and can be used as a filler and plasticizer in rubber compounds. This aligns with environmental sustainability principles, reduces disposal costs, and lowers raw material expenses in rubber manufacturing. In this research, the SBE was applied for each formula from SBE-02 to SBE-05 at ratios of 15–30 per hundred rubber (phr). As a comparison, carbon black (CB) filler (65 phr), CaCO3 (35 phr), and plasticizer derived from petroleum in the form of paraffinic oil (PO) (6 phr) were used. Rubber components were produced by masticating natural and synthetic rubber in an open mill, followed by the addition of filler, plasticizer, accelerator, co-activator, anti-degradant, and vulcanization agent. The resulting compounds were vulcanized at 150 °C and 10 MPa for 17 minutes. The test results demonstrated that incorporating SBE at a ratio of 15 phr (SBE-02) significantly reduced the cure time (t90) to 8 minutes and 20 seconds, the shortest among all tested formulations. The mechanical properties of the SBE-02 vulcanizate rubber met the requirements for solid wheelchair tire applications, with a hardness of 70 Shore A. However, its abrasion resistance test result of 189.1 g/cm³ was the lowest among the formulations tested. Furthermore, the scorch time (ts2) of the SBE-02 was determined to be 2 minutes and 35 seconds. Results from a 1000x magnification scanning electron microscope (SEM) reveal air gaps on all sample surfaces of different sizes. The elements C, O, Zn, Si, Ca, and Pb dominate the SEM-EDX results for all rubber vulcanizate samples from all three spectra, in varying weight percentages. The identification of functional groups with FTIR on all rubber vulcanizate samples shows Si–O–Si bending at 2, 4, and 5 and Si–O–Al stretching at 3, 5 on the wave number spectrum of 680–413 cm−1 Si–O–Si on the wave number spectrum 1100–1050 cm−1 from the infrared spectrum.

Preparation of aqueous silane‐graphene oxide co‐modified cellulose fibers/natural rubber composites via flash extrusion dispersion process

AbstractCellulose fibers were modified via aqueous silane‐graphene oxide (GO) coordination by flash drying and extrusion dispersion process. The adsorption of GO reduced the polarity of the cellulose fiber surface and attenuated the agglomeration effect between the cellulose fibers, thus facilitating the dispersion of fibers in the rubber matrix. Adding aqueous 3‐aminopropylsilane oligomer (8150) incorporated active sites on the surface of cellulose fibers, thereby improving the interfacial binding properties of cellulose nano fibers (CNFs) and natural rubber (NR). After blending the modified CNFs with NR latex, high‐temperature flocculation was performed using an atomised flash device. Finally, CNF/NR was pre‐dispersed through a twin‐screw extruder, after which a CNF/NR masterbatch with excellent performance was prepared. Experimental results revealed that composites prepared using GO‐8150 via the flash drying‐twin‐screw dispersion process exhibited excellent dispersion characteristics, processing properties, mechanical properties, rolling resistance, wear resistance, and heat generation properties. Compared with traditional dry mixing, the composites prepared by flash drying‐twin‐screw dispersion process showed a 16.95% increase in tensile strength, 16.07% increase in 300% constant elongation, 19.01% reduction in abrasion consumption, 42.26% reduction in rolling resistance, and a reduction in the Payne effect. This study offers an efficient and environmentally friendly method for the high‐value utilization of natural fibers and the preparation of NR composites with excellent properties, while providing a green and nonpolluting modification process with no acidic liquid discharge.Highlights GO‐8150 reduces the polarity of the fibers and promotes dispersion. The flash extrusion dispersion process achieves green flocculation. 42% lower rolling resistance for rubber composites.

Contrastive loss with dynamic margin for rubber-recipe physical-property prediction

Predicting the physical properties of rubber presents difficulties because of the intricate and nonlinear relationships between its constituent elements. The laborious nature of rubber manufacture results in restricted data sets, hence exacerbating this difficulty. To achieve successful training of a neural network with a smaller amount of data, it is crucial to use an appropriate weight initialization approach and carefully construct the network architecture to avoid overfitting. This study presents a novel approach to representation learning that uses a contrastive loss with dynamic margin loss function. The approach is specifically designed to capture semantic similarities in rubber material quantities and physical-property recipes. In addition, a novel neural network architecture is proposed that uses latent vectors for assigning initial weights. The proposed approach, validated using data from a rubber manufacturing company, showed a significant improvement of up to 30% in predictive accuracy for physical properties with a restricted amount of data.

Composites Based on Eucalyptus Nitens Leaves and Natural Rubber as a Valuable Alternative for the Development of Elastomeric Materials with Low Microbiological Impact.

The forest industry produces several low-value by-products, such as bark, sawdust, limbs, and leaves, that are not ultimately disposed of and remain in the forests and sawmill facilities. Among these by-products are leaves, which contain not only cellulose fibers and lignin but also essential oils such as terpenes. These are biosynthesized in a similar way as cis-1,4-polyisoprene. In this context, this work evaluates the use of screened and unscreened dried Eucalyptus nitens leaves in natural rubber. Among the most relevant results of this work is a significant increase in mechanical properties, such as tensile strength and elongation at break, reaching values of 9.45 MPa and 649% of tensile strength and elongation at break, respectively, for a sample of natural rubber containing sieved dried leaves of Eucalyptus nitens. In addition, it is observed that the content of this vegetable filler allows for inhibiting the antibacterial effect of vulcanized rubber against several bacteria, such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli K 12, Escherichia coli FT 17 and Pseudomonas fluorescens. These results are promising because they not only add value to a by-product of the forestry industry, improving the mechanical properties of natural rubber from a sustainable approach but also increase the affinity of rubber with bacterial microorganisms that may play a role in certain ecosystems.

Effect of alkaline protease content on the structure and properties of natural rubber

AbstractThe solidification technology of natural rubber exerts a significant impact on the properties of natural rubber. The solidification technology of alkaline protease has been highly valued by researchers at home and abroad because of its good solidification effect, excellent vulcanization performance, and low pollution. In this study, the effects of alkaline protease solidification technology and enzyme dosage on the structure and properties of natural rubber were investigated and compared with those of formic acid solidification technology. The solid‐state NMR results showed that increasing the enzyme dosage increased the molecular chain entanglements in the raw rubber. The gel content test results showed that the natural network structures (i.e. gels) increased after the addition of alkaline protease. The test results of the vulcanization characteristics showed that the addition of alkaline protease significantly shortened the positive vulcanization time. The Mw was the largest at an enzyme dosage of 0.07%. The test results for mechanical properties showed that the mechanical properties were best when the enzyme dosage was 0.07%. In addition, as the alkaline protease dosage increased, the Akron abrasion volume of natural rubber decreased, and the Akron abrasion volume was the lowest at an enzyme dosage of 0.07%.

Preparation, characterisation and enhanced fungistatic properties of silicone rubber with different concentrations of CMIT/MIT

Preparation, characterisation and enhanced fungistatic properties of silicone rubber with different concentrations of CMIT/MIT

Effect of Complex Well Conditions on the Swelling and Tribological Properties of High-Acrylonitrile Stator Rubber in Screw Pumps.

The effects of complex well conditions in shale oil wells on the swelling and tribological properties of high-acrylonitrile stator rubber used in screw pumps were investigated in this study. Tests were conducted considering the combined effects of immersion medium, temperature, and duration. The key parameters measured included mass change rate, volume change rate, hardness, elongation at break, tensile strength, surface micro-morphology of the rubber after thermal expansion and swelling, friction coefficient, and wear quantity. The results indicated that in the actual well fluids, the mass change rate of high-acrylonitrile rubber ranged from -1.08% to 1.29%, with a maximum volume change rate of 2.78%. In diesel oil, the greatest mass change rate of the rubber was 4.68%, and the volume change rate did not exceed ±1%, indicating superior swelling resistance. In both actual well fluids and diesel oil, the maximum decreases in hardness were 8.7% and 9.5%, respectively. Tensile strength and elongation at break decreased with increasing immersion temperature, with elongation at break in 80 °C diesel oil decreasing by over 50%, indicating a significant decline in the tensile properties of the rubber. The average friction coefficient of rubber specimens immersed in actual well fluids at three temperatures, as well as in diesel oil at 25 and 50 °C, decreased compared with the high-acrylonitrile rubber without thermal expansion and swelling. However, the average friction coefficient of rubber specimens immersed in diesel oil at 80 °C increased. The wear quantity of the rubber increased following immersion in both media. Additionally, the friction coefficient and wear quantity of the rubber increased with increasing immersion temperatures. The results of the study can offer valuable insights into assessing the durability of properties in high-acrylonitrile stator rubber under complex well conditions.

Impact properties of an end of life tires’ rubber. Numerical validation considering large strain and strain rate conditions

The objective of the authors is to demonstrate that the inclusion of renewed rubber from recycled end of life tires (ELT) can improve the performance of any structural system designed to dissipate impact energy. An interesting application would be its use in road safety barriers. This research starts with the rigorous characterization of the recycled material in order to include it in a viable numerical model. The authors presented, in a previous work (*), the experimental viscoelastic properties of recycled rubber, obtained under impact conditions. Bergström–Boyce (BB) nonlinear viscoelastic model was selected as the most suitable to fit the material behavior. This model is defined by nine material constants that are impossible to obtain, uniquely and directly, considering that only compression test results are available as input data. To overcome this challenge, optimization methods were applied resulting in as many sets of parameters as used optimization methods were considered and, moreover, remarkable differences between constants were observed. Solving this problem is the motivation of the present research: the validation of the optimization method by mean of the numerical evaluation of the obtained sets. The software considered for the numerical evaluation of impact tests (LS-DYNA®) had two slightly different implementations for the BB model: the original, based on the work published in 2009 by Dal & Kaliske and a more recent one implemented by Bergström, based on his works published in 1998 and 2000. This leads to a new question: which is the most appropriate implementation-optimization method for calibrating this material? This paper provides the answer to this question carrying out a complete comparative numerical analysis of all sets by means of explicit dynamics simulations. All calibrations, using the original LS-DYNA® implementation, were in perfect agreement with the experimental results. However, only one optimization method produced acceptable results for the most recent approach. A robust method to characterize recycled rubber from recycled tires using the Bergström–Boyce nonlinear viscoelastic model is presented, despite the experimental limitations (González-Vega et al. 2022).

Influence of preparation parameters on rheological properties and relation analysis of waste rubber modified bitumen mastic

Waste rubber modified bitumen has gained significant attention as a sustainable and innovative material in the field of pavement engineering. This study aims to evaluate the performance of rubber modified bitumen mastic by considering its rheological properties, specifically focusing on preparation parameters, i.e., rubber content, mesh number, and filler to bitumen ratio. From the experimental results, the rheological properties of rubber modified bitumen mastic were significantly influenced by preparation parameters. Increasing the rubber powder content in bitumen mastic results in higher viscosity. Increasing the rubber content improves high-temperature rutting resistance to a certain extent, however, excessive rubber powder content would result in weakened high-temperature performance improvement. The rutting factor decreases gradually with an increase in the rubber mesh number. A ratio of filler to bitumen of 0.95 exhibits the best resistance to rutting at high temperatures. Higher rubber content and larger mesh number correspond to stronger low-temperature crack resistance in bitumen mastic. As the ratio of filler to bitumen increases, the low-temperature deformation capacity gradually decreases, resulting in weaker low-temperature crack resistance. Based on the grey relation analysis, the ratio of filler to bitumen has the greatest impact on the high and low-temperature rheological properties of bitumen mastic, followed by the rubber content. The rubber mesh number has a relatively lower impact. It is crucial to control the ratio of filler to bitumen to avoid excessive values. When possible, a higher rubber powder content should be used while meeting process requirements. These findings provide valuable insights into the design and optimization of rubber modified bitumen mastic, which can contribute to the development of sustainable and high-performance bitumen mixtures, promoting the use of recycled rubber in pavement engineering.

Effect of hybrid filler comprising cryptocrystalline graphite and multi‐wall carbon nanotubes on the mechanical and conductive properties of styrene butadiene rubber

AbstractStyrene butadiene rubber (SBR) composites reinforced by cryptocrystalline graphite (CG) and multi‐wall carbon nanotubes (MWCNTs) were prepared. The SBR composite with 50 phr CG content displays superior mechanical reinforcement achieving 20.7 MPa in tensile strength. However, the electrical conductivity enhancement is modest. After incorporating MWCNTs as a secondary filler, the electrical conductivity significantly improved. The results show that the electrical conductivity of the SBR composite reinforced with 10 phr of CG and an additional 5 phr of MWCNTs surpasses that achieved by using 50 phr of CG solely. This enhancement can be attributed to the inherent excellent electric conductivity and high aspect ratio of MWCNTs, with their presence also preventing the re‐agglomeration of CG. Furthermore, within 10–40 phr content of CG, the mechanical reinforcement of CG‐SBR composites is enhanced with the addition of MWCNTs, whereas a minor decline in tensile strength is noted when the concentration of CG above 40 phr. Overall, the SBR composite reinforced with a synergistic combination of CG and MWCNTs is achieved, demonstrating both exceptional mechanical and conductive properties.Highlights Styrene butadiene rubber (SBR) composites with different cryptocrystalline graphite (CG) phr and additional multi‐wall carbon nanotubes (MWCNTs) were characterized. CG‐SBR displays good mechanical property but limited electrical conductivity. Proper ratio of CG/MWCNTs significantly enhances various properties. MWCNTs act as a “bridge” structure connecting isolated CG filler in SBR matrix. MWCNTs network effectively prevents the re‐agglomeration of CG nanosheets.

Effect of acoustic filler on sound insulation properties of millable polyurethane rubber

Effect of acoustic filler on sound insulation properties of millable polyurethane rubber

Rubber devulcanization in the planetary extruder – processing properties and structure

Thermo-mechanical devulcanization of ground tire rubber (GTR) in a planetary extruder was investigated. The processing parameters of recycled rubber were studied based on standardized protocols using a Mooney viscometer and a rubber processing analyzer (RPA). Fourier transform infrared spectroscopy and scanning electron microscopy were used to determine rubber structure. Devulcanization process upscaling limits processing properties of recycled rubber, which for partially devulcanized rubber can be determined only by RPA rheometer.

Preparation of Hydrophobic Modified Silica with Si69 and Its Reinforcing Mechanical Properties in Natural Rubber.

The inherent large number of hydroxyl groups of silica poses strong hydrophilicity, resulting in poor dispersibility in the natural rubber matrix. Here, the silica's surface was hydrophobically modified with [3-(triethoxysiliconyl) propyl] tetrasulfide (Si69) to improve the dispersibility and reinforce the mechanical properties of silica/natural rubber composites. The structure and morphology of modified silica were characterized by Fourier infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray electron spectroscopy (XPS), nuclear magnetic resonance spectroscopy and the contact angle. Further, the mechanical properties, dynamic mechanical properties and morphology of silica/natural rubber composites were studied with a universal electronic tension machine, dynamic thermal mechanical properties analyzer (DMA) and scanning electron microscope (SEM). The experimental results show that the Si69 was successfully grafted onto the surface of silica, thereby significantly improving the water contact angle (a 158.6% increase) and enhancing the mechanical properties of modified silica/natural rubber composites.

Utilization of agro waste activated carbons as carbon black replacement in electron beam irradiated styrene butadiene rubber composites

Purpose This study aims to prepare activated carbon (AC) and activated biochar (BC) from sugarcane bagasse (SCB) can be used as carbon black (CB) replacement for styrene butadiene rubber (SBR) composites cured by electron beam (EB) radiation. Design/methodology/approach This study is carried out to investigate the effect of partial replacement of CB (as traditional filler) by AC or BC prepared from low-cost agricultural wastes (SCB) to improve the properties of SBR rubber cured by EB radiation (doses from 25 to 150 kGy). Findings The results indicated that the addition of AC or BC leads to improve the physical and mechanical properties of SBR with increasing irradiation dose [especially at concentration of 10 parts per hundred part of rubber (phr) from BC]. Also in this study, this paper examines how exposure of SBR rubber composites to ultraviolet (UV) radiation changes the mechanical properties for these composites, to do that, the specimens were examined before and after they were exposed to UV radiation for 300 h. The results showed that, the irradiated SBR composites, UV exposure, exhibit better retention in mechanical properties as compared with unirradiated ones, and the samples loaded with CB hybrid with ACs had an increased value of tensile strength (TS) retention as compared with blank sample. Originality/value The importance of this study is that, the production of AC from SCB offers a huge opportunity to overcome the problem of the disposal of SCB.

Effect of recycled agricultural waste on fume emission and physicochemical properties of crumb rubber modified asphalt

Crumb rubber modified asphalt (CRMA) in the application process often produces lots of toxic fumes, and the composition is dominated by total volatile organic compounds (TVOCs) and H2S, which restricts its large-scale use in practical engineering. Therefore, three preferred agricultural wastes namely wood chip powder (WCP), peanut shell flour (PSF) and moxa stick ash (MSA) were added to CRMA to investigate their inhibition effect on CRMA fume in this work, and their inhibition mechanism on CRMA fume emission was discussed. Meanwhile, the influence effect of added agricultural waste on the physicochemical properties of CRMA was further analyzed and the modification mechanism was also explored. The experimental results indicate that the incorporated WCP, PSF and MSA can all inhibit the emission of TVOCs and H2S in CRMA to varying degrees. Compared with CRMA, the TVOCs concentrations of CRMA-WCP, CRMA-PSF and CRMA-MSA are reduced by 36.87 %, 11.72 % and 46.22 % under 190°C, respectively, while the H2S concentrations can be reduced by 53.45 %, 5.03 % and 62.67 %, respectively. The three agricultural wastes contain different mesoporous structures and their inhibition of CRMA fume is dominated by physical adsorption. Moreover, the added WCP, PSF and MSA can also synergize with crumb rubber to strengthen the rutting resistance of asphalt and upgrade the elastic recovery capacity of asphalt under different loads, and the enhancement effect is in the order of WCP > PSF > MSA. In summary, the three agricultural wastes preferred in this research are effective in suppressing the emission of toxic fumes from CRMA while improving its working performance, which can provide a new avenue for fume suppression in CRMA and multi-channel utilization of agricultural waste.

Synergistic Effect of Aluminum Nitride and Carbon Nanotube-Reinforced Silicon Rubber Nanocomposites.

Constructing a synergistic effect with different structural fillers is an important strategy for improving the comprehensive properties of polymeric composites. To improve the comprehensive properties of two-component additive liquid silicon rubber (SR) materials used in electronics packaging, the synergistic effect of granular aluminum nitride (AlN) and tubular carbon nanotube (CNT)-reinforced SR nanocomposites was investigated. AlN/CNT/SR composites with different AlN/CNT ratios were fabricated with two-component additive liquid SR via the thermal curing technique, and the influence of AlN/CNT hybrid fillers on the hardness, strength, elongation at break, surface resistivity, thermal conductivity, and thermal decomposition was investigated in detail. With the incorporation of AlN/CNT hybrid fillers, the comprehensive properties of the obtained AlN/CNT/SR composites are better than those of the AlN/SR and CNT/SR composites. The synergistic thermal conductive mechanism of AlN/CNT hybrid fillers was proposed and demonstrated with the fractural surface morphology of the obtained composites. The obtained AlN/CNT/SR composites show promising applications in electronic packaging, where necessary mechanical strength, electrical insulating, thermal conductivity, and thermal stable materials are needed.

Effect of Inorganic Fillers on Electrical and Mechanical Properties of Ceramizable Silicone Rubber.

Ceramizable silicone rubber (CSR) composed of silicone rubber matrix and inorganic fillers can be transformed into a dense flame-retardant ceramic upon encountering high temperatures or flames. Conventionally, CSR can be sintered into a dense ceramic at temperatures above 1000 °C, which is higher than the melting point of a copper conductor used in a power cable. In this study, the vulcanization process and mass ratio of inorganic fillers of CSR were studied to lower its ceramization temperature to 950 °C. The electrical and mechanical properties of CSRs and their ceramic bulks were studied with various ratios of wollastonite and muscovite. It was found that the CSR samples could be successfully fabricated using a two-step vulcanization technique (at 120 °C and 150 °C, respectively). As a high ratio of muscovite filler was introduced into the CSR, the sample presented a high dc electrical resistivity of 6.713 × 1014 Ω·cm, and a low dielectric constant of 4.3 and dielectric loss of 0.025 at 50 Hz. After the thermal sintering (at 950 °C for 1 h) of the CSR sample with a high ratio of muscovite, the ceramic sample exhibits a dense microstructure without any pores. The ceramic also demonstrates excellent insulating properties, with a volume resistivity of 8.69 × 1011 Ω·cm, and a low dielectric loss of 0.01 at 50 Hz. Meanwhile, the three-point bending strength of the ceramic sample reaches a value of 110.03 MPa. This study provides a potential route to fabricate CSR used for fire-resistant cables.

Mechanical and adhesive properties of RTV silicone rubber blended with silicone polyurethane modified epoxy resin

To enhance mechanical, adhesive, and thermal properties of Room Temperature Vulcanized (RTV) silicone rubber, a silicon-containing polyurethane/epoxy resin modifier (ESiPU) was developed. A three-phase system of polyurethane/epoxy resin/silicone rubber was prepared through blending, modification, and co-curing. FT-IR and 1H-NMR were employed to characterize the chemical structure of ESiPU. Microscopic analysis revealed improved compatibility between modified epoxy resin and silicone rubber. Mechanical testing showed significant enhancements in tensile strength, elongation at break, and adhesive strength, with RTV-20phr exhibiting increases of 236, 266, and 259%, respectively. Thermogravimetric analysis indicated higher initial decomposition temperature compared to pure RTV. At the same time, the char residue at 800 °C increased to 8.67%. TG-IR analysis demonstrated ESiPU’s ability to delay thermal degradation. Contact angle test confirmed improved hydrophobicity. Overall, the developed silicone rubber system exhibits promising mechanical and thermal properties, suggesting potential for aerospace heat protection applications.

Effect of cerium cysteine on the vulcanisation property and thermo-oxidative ageing of natural rubber

Effect of cerium cysteine on the vulcanisation property and thermo-oxidative ageing of natural rubber