Journal of Rubber Research最新文献

The focus of this study is on the evaluation of the effect of different types of inorganic fillers on the different major properties of natural rubber latex (NRL) foam vulcanisates. The mechanical and chemical properties of filled NRL foam were evaluated and compared with unfilled vulcanisate as per BIS standards IS 1741:2019 and IS: 6664 (1992) RA 2004 specification. The different fillers at various loadings selected for this study were marble powder, talc and China clay. From this study, talc was found to impart good mechanical properties such as indentation hardness index, flexing properties, compression set at constant strain and stress and split tear strength. It was also found that the chemical properties such as ageing resistance and water absorption properties for talc-filled foam were found to be equivalent to NRL foam without filler. Amongst the fillers studied talc possesses better mechanical and chemical properties followed by marble powder and China clay. Scanning electron microscope (SEM) image analysis of NRL foam at 500 μm scale with talc is self-explanatory to the above-mentioned facts.

Flexible antennas are placed near or on the human body without having an adverse effect on it. Therefore, they must be comfortable, flexible and not contribute to discomfort. At the same time, they must have a small value of the tangent of the angle of dielectric loss (tan δ_ε), a minimum absorption of electromagnetic power, the ability to withstand mechanical loads and have a small change in the complex dielectric permittivity in a wide frequency range. The aim of the study is to verify the possibilities of using spinel pigments as fillers in styrene-butadiene rubber composites applicable as substrates and insulating layers in flexible portable antennas for wireless communications. It was found that the filler used has characteristics that ensure good performance of the antenna, combined with an aesthetic appearance. The optimal concentration of the spinel pigment, which determines the best operational characteristics of the antenna, has been established.

Ethylene plays a role of gas hormone generated in response to varied stress in plant cells. In Hevea brasiliensis, periodic ethephon stimulation of tapped trees generates a dilution of the latex, a lower Total Solid Content (TSC) and a lower viscosity, resulting in a longer duration of the latex flow and a higher production of the following tappings. It also increases latex regeneration between two subsequent tappings. These mechanisms induce important changes in the laticifer metabolism and in the cellular genetic expression. Ethephon stimulation has become a major tool for tapping management. However, its excessive use can increase the susceptibility of trees to tapping panel dryness (TPD). A newly formulated ethephon water-based stimulant (RRIM HYDROBEST^TM, or RHB) is studied. A field trial was set with the clone RRIM 3001, comparing 4 stimulant treatments: ns = non-stimulated = control, ET = Ethephon 5%, MTX = MORTEX 5%, and RHB = RRIM HYDROBEST™ 5%. The production per tree was higher for MTX than for ns and ET, with RHB intermediate between both groups. The dry cut length (DCL) percentage of RHB was lower than that of ns, ET and MTX. Concerning the sucrose content of the latex measured in high-yielding and low-yielding periods, for the control ns alone, sucrose content in the low-yielding period was higher than that in the high-yielding period. Concerning the RHB treatment, in comparison with the control, 75 differentially expressed transcription factors were found, with most of them members of the ERF family. These results are discussed.

In this work, the mechanical behaviour of a thick-walled cylindrical pressure vessel composed of an incompressible isotropic non-linearly hyper-elastic material subjected to internal and/or external pressure is investigated. An analytical solution is proposed for the general form of the free strain energy density and different models including Neo–Hookean, Mooney–Rivlin, and Yeoh are employed. An analysis was conducted to determine the extension ratio at the inner and outer radii as well as the stress distribution, in different cases, namely the application of internal pressure only, external pressure only, and internal and external pressure applied simultaneously. In addition, various pressure values are applied to account for different levels of deformation. In order to strengthen the analytical solution, a finite element model of the pressurised vessel was constructed. A very good agreement has been found between the analytical predictions and the numerical results, suggesting the accuracy of the analytical solution. The analytical solution can be used for parametric studies (material or geometrical parameters) and the design/optimisation of a thick-walled cylindrical pressure vessel subjected to internal and/or external pressure. Additionally, it obviates the requirement for many finite element simulations, where computational cost is an important parameter.

Additive manufacturing, also known as 3D printing, is transforming the industry and becoming more common every day due to its considerable time saving and lower costs, compared to the established conventional manufacturing methods. The mechanical strength of 3D printed products is affected by the parameters of the 3D printing process. Thermoplastic Polyurethane (TPU) is a type of elastomer, capable of being used on any fused deposition modelling (FDM) 3D printer. A series of TPU test pieces with different infill density and patterns were produced using a FDM printer. The influence of infill parameters on the 3D part’s mechanical properties has been evaluated. Five patterns with a range of infill densities were compared in this study. The tensile properties of the printed specimens were influenced by the infill density, whereas the infill pattern used in this study has marginal effects. The grid pattern with 100% infill density showed the highest tensile strength, with a value of 4.43 MPa. The results were compared with specimens, which were prepared through conventional compression moulding. The dynamic mechanical thermal analysis (DMTA) and load–deflection analysis (LDA) tests showed that specimens with 100% infill density may not be significantly affected by different infill patterns selected in this study under low strain testing conditions.

Additive manufacturing (AM) involves creating prototypes by depositing and solidifying material by the placement of material in X, Y, and Z axes in a 3D space. The emergence of AM using elastomers has allowed the production of complex and customised parts with intricate geometries and modified properties as per specific needs of engineers cum designers. For successful 3D printing (3DP), it is crucial to use a material that is suitable for the specific application and printing process. Elastomers are unique polymers that are resilient, flexible and capable of deforming under stress. Fused deposition modelling, stereolithography and selective laser sintering printing are the most common 3DP techniques for elastomers. The use of elastomers in AM is limited due to technological, material and processing constraints. Despite challenges, elastomers have great potential in AM and can be applied in various industries namely automotive, aerospace, healthcare and consumer goods. However, there is a growing interest in expanding the range of elastomers that can be 3D printed. Researchers are experimenting with different approaches to enhance the printability of elastomers such as modifying material composition, material design, optimising printing parameters, control of chemical composition and 3DP techniques. Recent advancements in the structure, properties and printing techniques of elastomers show wide scope for improving their printability. Several elastomeric materials that can be 3D printed include thermoplastic elastomer, thermoplastic polyurethane, liquid silicone rubber, etc. This review paper aims at providing an overview of the current state of AM of elastomers, including the challenges and limitations. It discusses recent advancements and suggests ways to enhance the printability of elastomers in near future, which can help researchers and industry professionals to explore new and unique AM applications.

The presence of ammonia as a preservative in natural rubber (NR) latex concentrate induces a variety of problems in the NR latex foam manufacturing process, consequently leading to inconsistency in the quality of the end products. To overcome these issues, a novel ammonia-free NR (AFNR) latex concentrate that uses palm oil-based polymeric surfactants as an alternative preservative has been developed. This study explores the feasibility of using AFNR latex to produce latex foam shoe insoles. In this investigation, the AFNR latex was foamed into extra-high-density (EHD) and high-density (HD) foams using the Dunlop batch foaming process. The study found that HD latex foam is softer than EHD latex foam, with the Shore F hardness of HD latex foam and EHD latex foam being 57 and 77, respectively. The study also discovered that the peak pressure value and rebound resilience properties of HD latex foam shoe insoles, which were fabricated at 7 mm thickness, are 41% and 6% lower than those of EHD latex foam, respectively. Additionally, EHD latex foam and HD latex foam have different morphological characteristics, with EHD latex foam having a thicker cell wall, smaller pore size, and being less porous compared to HD latex foam. Taking these properties into consideration, HD foam could be the ideal choice for shoe insole applications, such as sports shoes.

In this work, the nanocomposites based on epichlorohydrin rubber (ECO) and graphene oxide (GO) have been prepared by solvent blending followed by open mill mixing, which is known to be an effective way of dispersing nanofillers within a polymer matrix. The successful dispersion of GO sheets within the ECO matrix has been confirmed by high-resolution transmission electron microscopy and atomic force microscopy. The incorporation of 1.5 vol.% of GO sheets into the ECO matrix enhances the breaking stress and stress at 200% strain values of ECO by 67% and 139%, respectively, which is due to the strong interfacial interactions between the polar groups in ECO and the oxygen-containing functional groups on the surfaces of GO sheets. This general finding is further corroborated by the fact that ECO's glass transition temperature increased from − 18 to − 14 °C with a 1.5 vol% GO content. The initial degradation temperature, the maximum degradation temperature and the percentage residue of ECO consistently increase with the concentration of GO due to the enhanced interfacial interaction between ECO and GO through chemical bonding, which delays the initial degradation by hampering the process of degradation. The uniform dispersion of GO sheets within the ECO matrix, along with improved interactions between GO sheets and ECO, results in the formation of a densely interconnected network of GO layers within the ECO chains. Consequently, this enhances the oil and fuel resistance of the ECO-GO nanocomposites. The fascinating results and outcomes of this investigation will pave the way for the development of fuel and oil-resistant materials with improved physico-mechanical properties.

Eucommia ulmoides rubber particles (EuRPs) are organelles that synthesise and store E. ulmoides rubber (EuR). In this study, the lipids dynamic change of EuRPs from leaf tissue at different growth period were investigated. The results showed that there were 1149 lipid species belonging to 39 lipid classes that were identified; TGs, DGs and Cers were the most abundant among all lipids of EuRPs. Lipid expression analysis demonstrated that the expression intensity of TGs was almost 1 × 10⁴-fold and 10-fold higher than those of MGs and DGs, respectively. Among sphingolipids, the expression intensity of SoP, CerG2, GM3, SM and GerG3 increased throughout the duration of investigation (August–November 2021). Further analysis found that the Cers species accounted for 9.40% of total lipid species and the number of Cers species in EuRPs isolated from leaves in August was the most, with gradual decline in the following 3 months. Meanwhile, hierarchical clustering indicated that there were seven types of highly abundant lipid species in leaf EuRPs from September to November, i.e. SQDG (18:3/18:3), SQDG (34:3), SQDG (17:5/23:2), DGDG (38:12), Co (Q9), TG (16:0/16:0/18:3) and TG (39:1). Compared with leaf EuRPs in August, there were 79, 101 and 107 lipid species which showed significant differential expression in September, October and November. Based on the high expression intensity of SQDG in EuRPs, the correlation between the genes mediated in EuR or SQDG biosynthesis was further analysed, whereby the results indicated co-expression of some genes, which implies the synergistic regulatory role in SQDG EuR biosynthesis.

Friction properties of rubber compounds are important for tyre tread applications as tyre is the only contact between the road and the car. Although epoxidised natural rubber (ENR) is widely reported to have a good grip property, there is limited information on its friction properties. In this study, the effect of substrate surface roughness on dry friction properties of tread rubbers based on silica-filled ENR 25 (ENR 25/silica), ENR 50 (ENR 50/silica) and NR (NR/silica) were assessed. Tensile strength, tear strength, hardness, dynamic properties and abrasion resistance were also examined. The friction properties upon sliding on a non-textured aluminium oxide plate and aluminium oxide abrasives with grit sizes of P320, P180, P120 and P60 were determined using the TE 75 Production Rubber Friction Tester at 5N, 10N, 15N and 20N of normal load. Meanwhile, surface roughness analysis on the sample surfaces was conducted using a 3D laser interferometer microscope. From this study, NR /silica tread had better physical strength, while ENR 50/silica had higher hardness and tensile modulus. On dynamic mechanical properties, the ENR 50/silica possessed the highest tangent delta value and all tangent delta values increased with a change of frequency from 1 to 10 Hz. With regard to friction properties, the coefficient of friction of all tread rubbers decreased with the increase in substrate roughness. The change in tread rubber surface roughness varied depending on the coefficient of friction, physical strength and substrate roughness. Throughout this study, the effect of surface roughness on dry friction properties of silica-filled ENR tread rubbers and its factors were successfully identified.