Hyperelastic Material Parameter Determination and Numerical Study of TPU and PDMS Dampers

Dampers provide safety by controlling unwanted motion that is caused due to the conversion of mechanical work into another form of energy (e.g., heat). State-of-the-art materials are elastomers and include thermoplastic elastomers. For the polymer-appropriate replacement of multi-component shock absorbers comprising mounts, rods, hydraulic fluids, pneumatic devices, or electro-magnetic devices, among others, in-depth insights into the mechanical characteristics of damper materials are required. The ultimate objective is to reduce complexity by utilizing inherent material damping rather than structural (multi-component) damping properties. The objective of this work was to compare the damping behavior of different elastomeric materials including thermoplastic poly(urethane) (TPU) and silicone rubber blends (mixtures of different poly(dimethylsiloxane) (PDMS)). Therefore, the materials were hyper- and viscoelastic characterized, a finite element calculation of a ball drop test was performed, and for validation, the rebound resilience was measured experimentally. The results revealed that the material parameter determination methodology is reliable, and the data that were applied for simulation led to realistic predictions. Interestingly, the rebound resilience of the mixture of soft and hard PDMS (50:50) wt% was the highest, and the lowest values were measured for TPU.

Identifying the Co-Curing Effect of an Accelerated-Sulfur/Bismaleimide Combination on Natural Rubber/Halogenated Rubber Blends Using a Rubber Process Analyzer

The rheometer curing curves of 50/50 blends of natural rubber (NR) and two different halogenated rubbers with a combination of conventional accelerated sulfur (CV) and 3 phr of a bismaleimide (MF3) at 170 °C indicates that a co-curing reaction has been taken place between NR and the halogenated rubbers via Diels–Alder reaction. To further confirm whether the co-curing reaction has taken place in the early stage of curing, a complex test methodology was applied with the help of a rubber process analyzer. In this test, the blends with CV and with CVMF3 were subjected to cure at 170 °C for a predetermined time so that both the CV and CVMF3 cured blends will have the same magnitude of curing torque. It is then cooled down to 40 °C and the storage modulus (G′) was evaluated as a function of strain from 0.5% to 100% at a constant frequency of 1 Hz. The results reveal that the blends cured with CVMF3 exhibit a higher G′ due to the enhanced network strength because of the formation of bismaleimide crosslinks than the same cured with only the CV system. The swelling resistance and the mechanical properties of the blends cured with CVMF3 were significantly higher than those cured with only the CV system.

The influence of silane on the physico-mechanical properties of vulcanizates using bentonite fillers

Layered phyllosilicate fillers have received attention in the polymer industry due to their unique nanoscale sheet-like structure. Adding a small amount of bentonite nanofiller gives rise to improved mechanical, thermal, and gas barrier properties of rubber mixtures. Depending on the application, natural bentonite is often modified by physical processes or by chemical processes (intercalation, cation exchange process, functionalization, pillaring, etc.). Chemical modification increases the size of the interlayer spaces and provides a hydrophobic environment. Functionalization (e.g., silanization), which encompasses the chemical grafting of thermally stable silane coupling agents onto the clay platelets, make inorganic bentonite and the organic polymer matrix compatible. In the introduced study, commercial bentonite P130 from Lieskovec deposit was modified by silane (3-aminopropyl trietoxysilane) treatment. Different techniques such as infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize modified and raw bentonite sample. Silanized P130s and raw product P130 were added to the natural rubber matrix to examine the influence of chemically functionalized bentonite on curing characteristic (M H, M L, t s2, t 90, ΔM) and mechanical properties (TSb, Eb, hardness) of rubber vulcanizates. Organo-bentonite was mixed into a rubber blend in particular ratio of 5, 10, 15, 20 phr in various combination with silane (3-aminopropyl triethoxysilane), Perkasil and carbon black. The highest maximum torque values were obtained with the sample using 20 phr of silanized P130s. The tensile strength (TSb) values decreased with increasing P130 content, as well as non-silanized and silanized P130. However, when 20 phr P130s was used, value of TSb was higher. The most enhanced properties of rubber blends were found with the addition of 20 phr of silanized bentonite P130s.

Curing characteristics and rheological properties of bentonite- filled rubber blends

The study deals with the examination of the rheological behaviour of rubber blends which were filled with bentonite. The filler - polymer as well as the filler - filler interactions were studied and determined from the frequency sweep and strain sweep rheological measurements. The used natural bentonite was extracted from the locality called Jelsovy Potok. The natural bentonite had a fine fraction with a particle size of 15μm a 45 μm and it was added into rubber blends as a partial replacement of commonly used filler. The rubber blends were characterised on the basis of curing characteristics (minimum torque ML, maximum torque MH, optimum time of cure t(c90), processing safety of blend ts,). Moreover, the complex viscosity and Payne effect were also specified. The required measurements were done by using PRPA 2000.

Hydrogenated Liquid Natural Rubber for Compatibility Enhancement of Poly(lactic acid) and Natural Rubber Blends

Non-catalytic hydrogenation of liquid natural rubber (LNR) via thermal decomposition of 2,4,6-trimethylbenzenesulfonylhydrazide (MSH) is reported in this study. Parameter studies of the hydrogenation reaction were performed by utilizing the combination of response surface methodology and central composite rotatable design (RSM/CCRD). The effects of each variable and the interaction between two variables (i.e. the MSH:LNR weight ratio and reaction time) were studied. Statistical analysis showed that the reaction time had significantly affected the hydrogenation percentage. A reduced quadratic model equation with the coefficient of determination (R2) value of 0.9875 was developed. The optimized condition as predicted by the software was compared with the experimental data, which deviated in only 0.67, hence indicating that this model was reliable and able to predict the hydrogenation percentage accurately. Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies were used to characterize the microstructure of LNR and hydrogenated liquid natural rubber (HLNR). HLNR was then used as compatibilizer to improve the miscibility of poly(lactic acid)/natural rubber blends. With an addition of 4% HLNR, the tensile strength and impact strength of the blends were slightly improved.