Degradation Of Styrene-butadiene Rubber Research Articles

Study of sequential abiotic and biotic degradation of styrene butadiene rubber

Styrene butadiene rubber is one of the main constituents of tire tread. During tire life, the tread material undergoes different stresses that impact its structure and chemical composition. Wear particles are then released into the environment as weathered material. To understand their fate, it is important to start with a better characterization of abiotic and biotic degradation of the elastomer material. A multi-disciplinary approach was implemented to study the photo- and thermo- degradation of non-vulcanized SBR films containing 15 w% styrene as well as their potential biodegradation by Rhodoccocus ruber and Gordonia polyisoprenivorans bacterial strains. Each ageing process leads to crosslinking reactions, much surface oxidation of the films and the production of hundreds of short chain compounds. These degradation products present a high level of unsaturation and oxidation and can be released into water to become potential substrates for microorganisms. Both strains were able to degrade from 0.2 to 1.2 % (% ThOD) of the aged SBR film after 30-day incubation while no biodegradation was observed on the pristine material. A 25–75 % decrease in the signal intensity of water extractable compounds was observed, suggesting that biomass production was linked to the consumption of low-molecular-weight degradation products. These results evidence the positive impact of abiotic degradation on the biodegradation process of styrene butadiene rubber.

Investigation of correlation between rheological properties of rubber compounds based on natural rubber/styrene-butadiene rubber with their thermal behaviors

Rubber compounds are widely used in many applications because of the properties they exhibit. The physical and mechanical properties of these blends are sensitive to small variations in the amount of the individual polymers used. Thermogravimetry is currently gaining wide acceptance as a method for compositional analysis of vulcanizates. Knowledge of the relationship among thermal behavior of rubber compounds with their rheological properties is important for the assessment of the optimum process conditions to produce materials that have required properties. The correlation of rheological properties of rubber compounds based on natural rubber/styrene-butadiene rubber with their thermal behavior has been assessed using thermogravimetry analysis. Thermogravimetric method permits the analysis to be completed in a short time and requires only a small sample. Thermogravimetry derivative profile (DTG) of the uncured blends and their rheological properties were investigated. Differential derivative curves of uncured vulcanizate showed that the degradation of styrene-butadiene rubber takes place at a higher temperature than that of natural rubber. According to DTG curves, two useful factors were demonstrated. These factors were the peak height ratio of natural rubber/styrene-butadiene rubber and a new factor called ‘normalized factor ,’ which could be correlated with the rheological properties of the blends. The result showed that the rheological nature of samples had acceptable correlation with the factors obtained by thermal analysis method. In other words, in this work a simple and reproducible experimental method was developed to efficiently predict the rheological properties of rubber blends.

Investigation of Mechanisms of Polycyclic Aromatic Hydrocarbons (PAHs) Initiated from the Thermal Degradation of Styrene Butadiene Rubber (SBR) in N2 Atmosphere

This study has been carried out to characterize the thermal decomposition of styrene-butadiene rubber (SBR), using thermogravimetric analysis (TGA) coupled to online GC/MS, and to investigate the formation and ultimate fate of chemical species produced during gasification of SBR. A preliminary mechanistic understanding has been developed to explain the formation and relationship of light hydrocarbons (C1-C4), substituted aromatics, and polycyclic aromatic hydrocarbons (PAHs) during the decomposition of SBR in a N2 atmosphere. Identification and absolute concentrations of over 50 major and minor species (from hydrogen to benzo[ghi]perylene) have been established, and the measurements have been carried out between 300 and 500 at 10 degrees C/min heating rate in a N2 atmosphere. The concentration of styrene reached 120 PPMV and the concentration of other substituted aromatics, such as toluene and ethyl benzene reached 20 and 5 PPMV, respectively. These measurements indicate PAH formation at a relatively lower temperature as compared to conventional fuel, such as coal and diesel. The PAH sequence is not simply the constructing of larger PAHs from smaller ones to achieve the complex polymer structures. It is possible to generate large PAH molecules while circumventing the typical construction pathway.

Thermal Degradation of Short Nylon-6 Fiber–Reinforced Styrene Butadiene Rubber Composite

ABSTRACT The thermal properties of short Nylon-6 fiber–reinforced Styrene butadiene rubber (SBR) composites were studied by Thermogravimetric Analysis (TGA). The effect of epoxy-based bonding agent on thermal degradation of the gum and the composites was also studied. The thermal stability of the SBR was enhanced in the presence of Nylon-6 fibers and the stability of the composites increased in the presence of bonding agent. The epoxy resin did not significantly change the thermal stability of SBR gum vulcanizate. Results of kinetic studies showed that the degradation of SBR and the short nylon fiber–reinforced composites with and without bonding agents followed first-order kinetics.

Thermomechanical Degradation of SBR During Ultrasonic Treatment under the Static Conditions

Abstract The paper presents the results of experimental and theoretical studies of the ultrasonic treatment of ground vulcanized unfilled styrene-butadiene rubber (SBR) in a static device (no flow). Degradation of the rubber network took place during the treatment. Crosslink density and gel fraction were measured in the samples ultrasonically treated at various pressures, ultrasonic amplitudes and exposure times. Consumption of the ultrasonic energy was also monitored. The structural characteristics of SBR ultrasonically treated under static conditions have been found to be significantly different from those reported previously for the continuous process. Theoretical calculations have demonstrated that the observed differences could be attributed to a partial depolymerization of broken rubber chains caused by a significant temperature rise in the course of ultrasonic treatment under static conditions. It has also been shown that the non-linearity of compressibility of a thin ground rubber layer has to be taken into account in the calculations of ultrasonic power consumption.

Kinetics of the Nonisothermal Degradation of Styrene-Butadiene Rubber

The kinetics of the thermal degradation of styrene-butadiene rubber (SBR) have been studied using a conventional nonisothermal thermo gravimetric technique at several heating rates ranging from 10°C/min to 50°C/min. The dynamic thermogravimetric analysis curve and its derivative have been analyzed using a variety of analytical methods reported in the litera ture to obtain the kinetic parameters such as activation energies, reaction or ders, and pre-exponential factors. When Freeman-Carroll's method is used, apparent activation energy ranging from 105.2-258.3 kJ/mol at various heating rates is given whereas the Flynn-Wall method gave values ranging from 220.9-344.3 kJ/mol. Friedman and Ozawa methods gave apparent activation en ergy between 55.0-237.0 kJ/mol and 75.3-305.1 kJ/mol upon fractional weight loss, respectively.

Accelerated Heat-Aging Studies on Fluororubber in Various Media

Abstract The nature, extent and, rate of chemical changes that take place in certain elastomers at long times is being studied. The chemical degradation of styrene-butadiene rubber (SBR) and fluorosilicone rubber (FVMQ) were reported previously. Investigations carried out with fluororubber (FKM) are discussed in this paper. Like fluorosilicone, this fluorocarbon elastomer is regarded as a high-temperature- and hydrocarbon-fuel-resistant rubber. The designation FKM is given to the copolymers of vinylidene fluoride (VF) and perfluoropropylene (PFP). The one discussed here is reported to contain also small quantities of a third component, tetrafluoroethylene. The detailed structure, assigned to the FKM polymer as a result of nuclear magnetic resonance studies, shows that it consists of blocks of VF homopolymer, 95% of which is head-to-tail, and blocks of VF-PFP copolymer, 93% of which is head-to-tail. The ratio of the copolymer to the VF homopolymer is dependent on the mole fraction of VF used. Vulcanization of FKM with derivatives of diamines is the commercially preferred method, although peroxides and high-energy radiation can be used for the same purpose. In the present study, N, N-dicinnamylidene-1,6-hexanediamine a Schiff 's base of 1,6-hexanediamine, was used with magnesium oxide as the acid acceptor. Chemical stress relaxation was the method most extensively used to determine the network changes taking place in the heat-aged fluororubber. Swelling, gel permeation chromatography (gpc), and infrared (ir) spectroscopy were also used to obtain additional information.

Important Stability Factors for Styrene-Butadiene Rubber

Abstract (1) Styrene-butadiene rubber (SBR) is very susceptible to oxidative degradation unless an effective stabilizing agent is incorporated in the polymer during manufacture. (2) Degradation of SBR appears as discoloration or resinification during drying of the polymer or during storage. Changes in the polymer may appear as variation in Mooney viscosity or as an increase in gel content. (3) Deterioration of inadequately stabilized SBR may also show up during processing operations when the polymer is subjected to heat—as in the Banbury or on a hot mill. (4) Deterioration of SBR polymer will appear as degraded physical properties in the cured vulcanizate. (5) The rubber goods manufacturer will benefit from the use of a really effective SBR stabilizer incorporated in the polymer during manufacture or by adding additional stabilizer to provide more protection against heat degradation in his operations. (6) Tris(nonylated aryl) phosphite exhibits unusual effectiveness as a stabilizer for SBR. (7) The presently widely used method of salt-acid coagulation of SBR polymer leaves room for improvement as far as polymer stability is concerned. (8) The more effective SBR stabilizers exhibit benefits in the aging of SBR vulcanizates.