Papers by Keyword: Rubber

Abstract: Recycled rubber materials are one of cheap and suitable materials for energy absorbers in protective structures. Standard tests of elastomers in uniaxial or biaxial tension is not suitable and efficient for energy absorbers made of recycled car tires. Simple compression test and simple impact test are described material properties from those tests are determined and compared with simulation in ANSYS/AUTODYN.

Abstract: STR-5L is a high quality block rubber in Thailand that is interesting to apply in medical and pharmaceutical products because it has very low impurity but high uniformity. In this study, medicated pressure sensitive adhesive (PSA) patches were developed by melt blending technique using hydroxyethyl cellulose (HEC) as tackifier and paraffinic oil as softener. Two rolls mill was used to blend all ingredients and the thin PSA patches were rolled out. Various preparation parameters were studied such as initial viscosity of rubber (60 or 80 Mooney viscosity; MV), mastication time (5-20 minutes), step of mixing, mixing time (35-80 minutes) and gap between rollers (0.1-0.4 mm). The suitable processing conditions were optimized. It was found that the rubber having initial viscosity of 80 MV provided better physical properties, for example, higher force T-peel, lap shear strength and shear holding time. Longer mastication time increased the shear holding time of patches. At 70 minutes of mixing time, the patches showed the highest shear holding time and did not leave any residue on the testing equipment surface. Moreover, the shear holding time decreased when the gap between rollers was expanded. Mixing method with the sequential addition of STR-5L, HEC and then paraffinic oil, provided good PSA patches. However, preparation process did not affect the plasticity retention index of PSA patches due to there were not significant change of values when those all parameters were varied. Next, lidocaine or its hydrochloride salt in powder form could be blended into this PSA to be the homogeneous patches. This lidocaine PSA patches for local anesthetics application on the skin would be evaluated in further study.

Abstract: The microwave absorbing rubber was prepared by adding the microwave absorber PPy/Ni/NanoG and other additives into NBR rubber. By analysis, the proper contents of N330, DOP and PPy/Ni/NanoG are 60, 10 and 25, respectively. The reflection loss of the rubber is below-10 dB at 8.2~11.4 GHz and the minimum loss value is-14.58 dB at 9.76 GHz.

Abstract: With the rapid development of modern technology and industry, new high-damping materials with comprehensive performance were expected to be invented. Initially, the stress relaxing performance of CIIR/HBP-OMMT composites was investigated. Then, the solvent resistance, crosslinking density, and anti-aging properties of these composites were tested and analyzed. Results demonstrated that this organoclay may improve the damping together with other physical properties of these composites.

Abstract: This study presents the results of the experimental study on the axial compressive behavior of the rubberized concrete under active confinement. Two different mixes of concretes with rubber replacement ratios of 0%, as a control mix, and 18% were prepared. The effects of the incorporation of rubber and the confining pressure on the compressive behavior of concrete were examined through tests of unconfined and actively confined concrete cylinders. The active confinement was applied by a Hoek cell at different pressures, including 5, 7.5, 10, 15, 20, and 25 MPa. The results indicate that the rubberized concrete exhibits lower compressive strength but higher axial and lateral deformation capacities than those of the conventional concrete.

Abstract: The vulcanization or curing process begins in a heated mould to convert viscous uncured rubber materials into functional elastic ones. As the mechanical properties and service performances of the final products are greatly affected by the state of cure or cure level of rubbers, thus it is very crucial to use suitable time, pressure and temperature for the curing process to ensure that the desired quality of the final products are obtained. A computer program “RACE-CURE” written in standard FORTRAN code has been developed by our research team for the analysis of curing process of large rubber parts. The program is developed based on the incremental finite element formulation for three dimensional nonlinear transient heat transfer analysis coupled with cure kinetics. The RACE-CURE is tested for a test problem of curing of a large rubber block and results are compared to another two programs: ANSYS Polyflow v.14 and CFEM, a MATLAB© FEM program with capability to add curing kinetics, independently developed at our research group.

Abstract: Bearings of small turbo machines support high speed rotors rotating with the frequency over 1 [kHz]. Such bearings are often supported with O-rings made of soft materials like rubber to attenuate high frequency oscillations. Dynamic properties of rubber supporters have been measured experimentally for individual dimensions, but the universal prediction of dynamic properties for various frequencies is difficult not only because rubbers exhibit nonlinearity against its strain, but because O-ring supporters deform heterogeneously. For the precise prediction, it is necessary to investigate the viscoelasticity of rubber under various deformations and frequencies. Such properties can be measured by the standard shear vibration non-response method of ISO 6721-6 (JIS K 7244-6). However this is applicable only to low frequency range under 100 [Hz] because of the limitation of resonance frequency of the load cell. In this research, based on BERM (Base Excitation Resonant Mass) method, a new method was developed to measure the complex shear modulus at high frequencies up to 1 [kHz] of rubber sheets under homogeneous shear deformations. In the presented method, the force is calculated from the acceleration of the mass instead of the direct measurement by a load cell. Hence accurate measurement became possible even in the range beyond the resonance frequency of a load cell. The measured shear storage modulus G’ and shear loss modulus G” of deformed rubber were presented.

Abstract: Excellent material can improve the function of water lubricated stern bearing. According to the material properties and the theory of operational research, the mathematical model of the optimal selection material of water lubricated rubber bearing is established. The condition of selecting materials is discussed. The expression of the maximum value is obtained by using software. The influence of material properties on the objective function is discussed.

Abstract: Railtrack ballast is a component in the track’s substructure. It plays the important role of transmitting and distributing the wheel load to the deeper track section, i.e. subgrade. The cause of ballast breakage is often due to repeated impact by the passing trains. Mostly the breakage occurs at the sharp corners of ballast. Oil contamination can also contribute to track deterioration. In this manner, caused by fuel leaking from the rolling stock and maintenance works of trains. Therefore, it results in shear strength reduction of the ballast layer as the ballast loose frictional resistance due to the oil contamination. In this study, a series of direct shear test were conducted in a shear box measuring 60 mm x 60 mm x 25 mm. The rubber inclusion of circular patches (dia. 15 mm) was derived from the inner rubber tube of motorcycles tyres. Gravels of suitable sizes were sieved and used as representative samples of the ballast. Prior to the test, the gravels were soaked with lubricant oil for 14 days to simulate the contamination. Shear strength of dry and oil contamination ballast, with or without circular patches were then compared. The test results indicated that contact between rubber and ballast when the circular patches exposed to the oil-contaminated gravels (lubricant oil) could improve the shear resistance and have a better deformation. It was observed that the deformation of the oil-contaminated with circular patches was reduced compared to the ballast without circular patches. The improvement of shear resistance is due to the increased ductility of composite and breakage control. It is with nothing that the present study were conducted is static in a scaled down model. Therefore, it is necessary for the future research to be conducted with full-scale test under dynamic loading to mimics the actual rail traffic.

Abstract: Utilization of waste materials such as waste tire rubber in the building industry can help prevent environmental pollution whilst contributing to the design of more economical buildings. Preliminary studies show that workable rubberized portland cement concrete mixtures can be made provided that appropriate percentages of tire rubber are used in such mixtures. This article provides the overview of some of published paper using tire waste rubber in portland cement concrete. The researchers mostly investigated the properties of fresh and hardened concrete. The workability, density, air content, unit weight, compressive strength, modulus of elasticity, freezing and thawing resistance, abrasion resistance and thermal properties of the waste tire rubber in concrete were discussed.