Property deterioration in reactive elastomeric terpolymer modified binders during storage at elevated temperatures

This study investigates the effect of storage temperature, storage time, base binder, polymer type, and poly-phosphoric acid (PPA) concentration on the properties of commercial-grade reactive elastomeric terpolymer-modified binders (RET-MBs). To mimic the practical storage conditions, RET-MBs were contained in sealed metal tubes and stored in a forced convection oven at temperatures 120, 135, 150, and 165 degrees C for up to 14 days. The results show that the deterioration in conventional and rheological properties of RET-MBs was noticeable even at a low storage temperature of 135 degrees C. At storage temperatures of 150 and 165 degrees C, significant property erosion was observed within the first three days of storage. After 7 days of storage at 150 degrees C, the softening point temperature, the PG upper temperature (T-u), and percent elastic recovery values decrease by 4 degrees C, 3.5 degrees C, and 45%, respectively. One PG-grade drop can occur after 3-7 days of storage at 150 and 165 degrees C, which can result in the RET-MB failing the required specification. FTIR analysis of the solution-cast films of RET polymer with PPA reveals the interaction of the epoxy ring with PPA molecules to form phosphate ester linkage during storage, due to which the interaction between RET polymer and binder molecules reduces, resulting in severe property erosion during storage. The result demonstrates that RET-MBs should be stored and transported at temperatures < 135 degrees C, and this specific storage requirement must be mentioned in the storage and handling guidelines for RET-MBs.