Effect of the processing conditions and the addition oftrans-polyoctenylene rubber on the properties of natural rubber/styrene–butadiene rubber blends (original) (raw)
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This paper focuses on the use of styrene butadiene rubber (SBR) as a viscosity modifier in novel blends of natural rubber (NR) and dichlorocarbene modified styrene butadiene rubber (DCSBR). The processing characteristics, vulcanisation kinetics, stress-strain behaviour, mechanical properties and low temperature transition of the blends have been examined in order to analyse the influence of SBR in the blends. The change in cross-link density values from stress strain behaviour and equilibrium swelling data has been correlated with the technological properties of the blends. The excellent mechanical properties and the increased cross-link density in blends in the presence of 5-10 phr of styrene butadiene rubber reveals the viscosity modifying action of SBR in NR/DCSBR blends. The variation in viscosities of these blends with the addition of SBR is reflected in the DSC thermograms. The resulting blends show very high resistance to thermal ageing as compared to those without SBR.
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.
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.
Study of two types of styrene butadiene rubber in tire tread compounds
Polymer Testing, 2001
The ratio of vinyl butadiene and styrene groups in styrene butadiene rubber (SBR) structures is a crucial factor that affects the inherent rubber characteristics such as glass transition temperature, T g , hysteresis, strength, etc. In this paper, two types of SBR (Krynol 1721 and Buna VSL 5025-1) which contain higher ratios of these two groups, were blended with natural rubber (SMR 5) and compared with a blend of general purpose SBR (Krynol 1712) and SMR 5. The results show that the blends with the two rubbers possess a markedly lower resilience (i.e. higher hysteresis) than that of the general purpose SBR. Besides resilience, other properties of the compounds, Mooney viscosity, scorch time, cure time, tensile strength, tear strength, and ageing resistance were also investigated. At a similar blending ratio of 50:50, blends with Krynol 1721 and Buna VSL 5025-1 show markedly lower rebound resilience while other mechanical properties are considered acceptable. This preliminary investigation indicates that the two rubbers are suitable for wet grip improvement. Subsequently, the ratio of Krynol 1721 and Buna VSL 5025-1 in the blends was varied from 30 to 70 phr. As the ratio of the rubbers is increased, a reduction in rebound resilience is also observed and the effect of Buna VSL 5025-1 is more pronounced than Krynol 1721. The result is consistent with the higher T g of the former. Mooney viscosity, scorch time, cure time and ageing index (based on tensile strength) are increased but there is a slight drop in tensile strength and tear strength.
Elastomers based on NR/BR/SBR ternary rubber blend: Morphological, mechanical and thermal properties
Chemical Industry and Chemical Engineering Quarterly
The elastomeric materials based on NR/BR/SBR ternary rubber blend were investigated. The polyisoprene (NR), butadiene (BR) and styrene butadiene (SBR) rubbers were used as network precursors and carbon black (CB) as an active filler (60 phr) for elastomeric materials preparation. For sample preparation, the mass ratio of NR to BR was constant, 1:1, but the SBR content was varied from 0 to 80 phr. The morphological, mechanical and thermal properties of prepared elastomeric materials were determined using scanning electron microscopy (SEM), mechanical tensile measurements and thermogravimetric analysis (TGA). Mechanical properties were assessed before and after thermooxidative aging during 168 h at 100 ?C. The values of tensile strength, elongation at break, and hardness decrease up to 40 phr of SBR content and after that are increasing, but abrasion resistance of ternary rubber blends increases. ?he thermal decomposition temperature obviously shifted to a higher temperature for the s...
The effects of tensile and morphological properties of styrene butadiene rubber/virgin chloroprene rubber blends (SBR/CRv) and styrene butadiene rubber/recycled chloroprene rubber blends (SBR/CRr) were investigated. The range size of CRr used in this study was 0.3 – 0.7 mm. Both SBR/CRv blends and SBR/CRr blends were prepared using two roll mill at room temperature with blend ratios 95/5, 85/15, 75/25, 65/35 and 50/50. It can be observed that, cure characteristics of SBR/CRr blends have lower cure time, t90 than SBR/CRv blends.SBR/CRr blends showed higher scorch time, t2 and minimum torque (ML) compared to SBR/CRv blends at all blend ratios compared with the SBR/CRv blends. However, maximum torque (MH) of SBR/CRr blends exhibit the opposite trend compared with the SBR/CRv blends. It can be observed that, the tensile strength and elongation at break of SBR/CRr blends show higher value than SBR/CRv blends particularly up to 15 phr of CRr in the blends. However, SBR/CRr blends shows higher value of tensile modulus (M100) than SBR/CRv blends at all blend ratios. The scanning electron microscopy (SEM) of tensile fracture surface of SBR/CRr blends at 50 blend ratios illustrated a better adhesion and dispersion in comparison with SBR/CRv blends.
About the cure kinetics in natural rubber/styrene Butadiene rubber blends at 433K
Physica B: Condensed Matter, 2012
Vulcanized blends of elastomers are employed in several goods mainly to improve physical properties and reduce costs. One of the most used blends of this kind is that composed by natural rubber (NR) and styrene butadiene rubber (SBR). The cure kinetic of these blends depends mainly on the compound formulation and the cure temperature and time. The preparation method of the blends can influence the mechanical properties of the vulcanized compounds. In this work the cure kinetic at 433 K of NR/SBR blends vulcanized with the system sulfur/TBBS (N-t-butyl-2-benzothiazole sulfenamide) is analyzed in samples prepared by mechanical mixing and solution blending. The two methods produce elastomer domains of NR and SBR, which present different microstructure due to the cure level attained during vulcanization. The cure kinetics is studied by means of rheometer tests and the model proposed by Kamal and Sourour. The analysis of the cure rate is presented and is related to the structure obtained during the vulcanization process.
2010
The effects of epoxidized natural rubber (ENR-50) as a compatibilizer on the properties of styrene butadiene rubber/recycled acrylonitrile-butadiene rubber (SBR/NBRr) blends were studied. Styrene butadiene rubber/recycled acrylonitrile-butadiene rubber (SBR/NBRr) blends were prepared by two-roll mill with five different compositions (i.e., 85/5/10, 75/ 15/10, 65/25/10, 55/35/10 and 40/50/10), with the ENR-50 content fixed at 10 phr. Cure characteristics, mechanical properties, FTIR analysis, differential scanning calorimetry (DSC) and morphology (SEM) studies were performed to determine the compatibility of SBR/NBRr blends in the presence of ENR-50. The cure characteristics showed that SBR/ NBRr blends with the presence of ENR-50 have lower scorch time t 2 and cure time t 90 than SBR/NBRr blends without ENR-50. The SBR/NBRr blends with ENR-50 exhibited lower minimum torque (M L) compared with SBR/NBRr blends without ENR-50, which indicates better processability of the blends after compatibilization. However, SBR/NBRr blends with ENR-50 exhibited a higher value of maximum torque (M H) than SBR/NBRr blends without ENR-50. The incorporation of ENR-50 improved the tensile strength and tensile modulus (M100, stress at 100% elongation) of SBR/NBRr blends with ENR-50 compared with SBR/ NBRr blends without ENR-50 at all blend ratios. Nevertheless, the addition of ENR-50 reduced the elongation at break (E b) and rebound resilience of compatibilized SBR/NBRr blends compared with SBR/NBRr without ENR-50. The improvement in hardness upon compatibilization is due to an increase in crosslink density. FTIR analysis showed that ENR-50 is compatible with NBRr through the oxirane group and with SBR through the isoprene group. Differential scanning calorimetry results show an improvement in the compatibility of SBR/NBRr blends with the presence of ENR-50. Scanning electron microscopy (SEM) of the fracture surfaces indicates that, with the addition of ENR-50 in SBR/NBRr blends, better adhesion between SBR and NBRr was obtained, thus improving the compatibility of SBR/ NBRr blends.