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

Background: 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. Results: 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 (h(NRx)/h(NR100)/h(SBR100-x)/h(SBR100)),' which could be correlated with the rheological properties of the blends. Conclusions: 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.