Effect of additives on the thermal stability of SBS modified binders during storage at elevated temperatures

Abstract

Styrene-butadiene-styrene modified binders (SBS-MBs) exhibit significant property deterioration during storage at elevated temperatures (≥180 °C) in closed containers due to the degradation of the SBS molecules. This study examines the effect of waxes, polyphosphoric acid (PPA), thermal stabilizers, sulfur, aromatic oils, and oxidized binders on the thermal stability of SBS-MBs. The result shows that iscowax and PPA successfully reduced property deterioration in SBS-MBs during storage at 180 °C by up to 30–40 %. On the other hand, thermal stabilizers are ineffective in enhancing the thermal stability of SBS-MBs in closed containers where the presence of air/oxygen is limited. Similarly, sulfur, aromatic oil, and oxidized binders do not alter the thermal stability of SBS-MBs. SBS polymer with high vinyl content (≥30%) showed excellent thermal stability during storage at 180 °C. The shifting of the CC bond from the main chain to the side chain (vinyl content) shields the chain scission of the SBS polymer at elevated temperatures. This study provides practically implementable mitigation strategies, such as using iscowax, PPA, and high vinyl content SBS polymer, to safeguard the properties of SBS-MBs during storage and transportation. These strategies can be adopted by users and suppliers of SBS-MBs in scenarios where prolonged storage at elevated temperatures is required.