Quantitative characterization of interfaces in rubber-rubber blends by means of modulated-temperature DSC

Rubber-rubber blends are used widely in industry, for example, in tire manu facture. It is often difficult to characterize interfaces in such rubber-ru bber blends quantitatively because of the similarity in the chemical struct ure of the component rubbers. Here, a new method was suggested for the meas urement of the weight fraction of the interface in rubber-rubber blends usi ng modulated-temperature differential scanning calorimetry (M-TDSC). Quanti tative analysis using the differential of the heat capacity, dCp/dT, versus the temperature signal from M-TDSC allows the weight fraction of the inter face to be calculated. As examples, polybutadiene rubber (BR)-natural rubbe r (NR), BR-styrene-co-butadiene rubber (SBR), SBR-NR, and nitrile rubber (N BR)-NR blend systems were analyzed. The interfacial content in these blends was obtained. SBR is partially miscible with BR. The cis-structure content in BR has an obvious effect on the extent of mixing in the SBR-BR blends. With increasing styrene content in the SBR in the SBR-BR blends, the interf ace content decreases. NR is partially miscible with both BR and SBR. The N BR used in this research is essentially immiscible with NR. The maximum amo unt of interface was found to be at the 50:50 blend composition in BT-NR, S BR-BR, and SBR-NR systems. Quantitative analysis of interfaces in these ble nd systems is reported for the first time. (C) 2000 John Wiley & Sons, Inc.