Investigations on the addition of styrene butadiene rubber in natural rubber and dichlorocarbene modified styrene butadiene rubber blends (original) (raw)
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Cure Characteristics and Crosslink Density of Natural Rubber/Styrene Butadiene Rubber Blends
Jurnal Teknik Kimia USU
By using a semi-efficient vulcanization system, the cure characteristics and crosslink density of natural rubber/styrene butadiene rubber (NR/SBR) blends were studied with a blend ratio from 0 to 100% rubber. The scorch time, optimum cure time, and torque difference value of the blended rubber compounds were determined by using the Moving-Die Rheometer (MDR 2000). The crosslink density was determined by the Flory—Rehner approach. Results indicate that the scorch and cure times, ts2 and t90, of the NR/SBR blends increased with increasing the SBR content. Whilst, the maximum values of torque difference and crosslink density were performed by the NR/SBR blend with a blend ratio of 75/25.
Characterization of gradual styrene-butadiene rubber blends
Materials Letters, 1992
Blends of gradual styrene-butadiene rubbers (SBRs) were prepared from linear SBRs of narrow molecular weight distribution synthesized by anionic polymerization. Blends were made either by mixing polymer solutions and then evaporating the solvent or by mixing desiccated solid SBRs. We demonstrate that the morphology of the fractured surfaces, examined by scanning electron microscopy, and the mechanical properties depend strongly on the mixing procedure and on the SBRs' compatibility.
Studies on the cure and mechanical properties of natural rubber blends
This paper focused on the comparative evaluation of cure characteristics and mechanical properties of blends of natural rubber with dichlorocarbene modified styrene-butadiene rubber and chloroprene rubber with different blend composition. It was found that the Mooney scorch time and cure index shows a negative deviation from the calculated value based on the interpolation between the two component elastomers. However for the blends, modulus and hardness show a positive deviation. The mechanical properties of NR/DCSBR blend are higher than that of NR/CR blends. Flammability, oil and ozone resistance of the blend showed that as the NR content in the blend increases these properties were decreases and also NR/DCSBR blend showed excellent thermal, oil and ozone resistance than that of NR/ CR in entire blend ratios. The mechanical properties, modulus and hardness were also investigated after oil immersion. The changes in mechanical properties were correlated with variation in cross-link density estimated from stress-strain and swelling behavior.
Journal of Applied Polymer Science, 2003
The morphology, mechanical and viscoelastic behavior of latex blends of unvulcanized natural rubber (NR) with carboxylated styrene-butadiene rubber (XSBR) were investigated, with special reference to the effect of the blend ratio, temperature, and frequency. Mechanical properties like tensile strength, modulus, and elongation at break were also studied. As the XSBR content increased, the tensile strength increased up to a 50:50 NR/XSBR ratio and then decreased as a result of the self-curing nature of XSBR. The dynamic mechanical properties of these latex blends were analyzed for loss tangent, storage modulus, and loss modulus. The entire blend yielded two glass-transition temperatures, which corresponded to the transitions of individual components, indicating that the system was immiscible. To determine the change in modulus with time, a master curve of 50:50 NR/XSBR blends was plotted. Time-temperature superposition and Cole-Cole analysis were done to understand the phase behavior of the latex blends. The experimental and theoretical values of storage modulus of blends were compared using the Kerner and Halpin-Tsai models. With the help of optical micrographs, attempts were made to correlate the morphology and viscoelastic behavior of these blends.
Effect of Rubber Blend Compositions on Their Mechanical and Oil Resistance Characteristics
The International Conference on Chemical and Environmental Engineering (Print), 2008
Polymer blends represent a field of intensive research. In the present work, different rubber blends based on nitrile butadiene rubber, NBR (N3980-39% acrylonitrile) have been selected to get a product with high oil resistance and good mechanical properties. The ratio of each component (NBR and chloroprene rubber CR) in NBR-CR blends has been varied and the corresponding vulcanizing systems have been carefully selected. The rheological properties of the different blends obtained were evaluated. For instance, the scorch time, optimum time of vulcanization have been determined and correlated with the blends composition. The mechanical properties, swelling in toluene and different oils have been evaluated using standard techniques. Besides, the effects of different vulcanizing systems on the mechanical properties and degree of swelling of the vulcanized blends in toluene, as well as the resistance of the blends to the oils has been evaluated. It has been found that the type of rubber and the composition of blends clearly affect their resistance to oils. In contrast, the type of crosslinking and crosslinking density slightly affect the oil resistance of the corresponding vulcanizates.
Temperature dependence on free volume in cured natural rubber and styrene-butadiene rubber blends
Physical Review E, 2011
A systematic study on the evolution of free volume as a function of the temperature in vulcanized at 433 K natural rubber (NR) and styrene butadiene rubber (SBR) in 25-75, 50-50, 75-25 NR-SBR (percent content of pure NR and SBR, respectively) blends was studied by positron annihilation lifetime spectroscopy. All samples were prepared with sulfur and TBBS (n-t-butyl-2-benzothiazole sulfenamide) as accelerator. The glass transition temperatures of the samples studied were determined by differential scanning calorimetry (DSC) and from lifetime data. In general, a sigmoidal-like complex behavior of the long-lived lifetime component, linked to the nanohole free volume, as a function of the temperature was found. For SBR, the slope of the ortho-positronium lifetime against temperature curves could be well-fitted using a linear function. For blends and also for NR, two different linear functions were necessary. This last behavior is explained in terms of the supercooled process involving a reconfiguration of the elastomeric chains. In the case of blends, the state of cure of NR and SBR in each NR-SBR sample was also taken into account in the discussion of the results obtained. Besides, thermal expansion coefficients of the free volumes in the transition and glassy region of all compounds were estimated. The differences observed in the values of this parameter are discussed by taking into account the morphology and formulation of each blend, the crosslink densities, and the role of the interphases formed between both NR and SBR elastomers.
Polymer International
The present work focuses on the compatibization of styrene-co-butadiene rubber (SBR)/acrylonitrile-co-butadiene rubber (NBR) blends with dichlorocarbene modified styrene-co-butadiene rubber (DCSBR) as a function of concentration of compatibilizer and composition of the blend. FTIR studies, differential scanning calorimetry and dynamic mechanical analysis reveal molecular level miscibility in the blends in the presence of compatibilizer. The formation of interfacial bonding is assessed by analysis of swelling behaviour, cure characteristics, stress–strain data and mechanical properties. These studies show that the compatibilizing action of DCSBR becomes more prominent as the proportion of NBR in the blend increases. The resistance of the vulcanizate towards thermal and oil ageing improved with compatibilization. The change in technological properties is correlated with the crosslink density of the blends assessed from swelling and stress–strain data.© 2001 Society of Chemical Industry