Synthesis of polyesters derived from glycerol and phthalic anhydride and its application for bitumen modification

This study introduces phthalic anhydride (P) and glycerol (G)-based polyester as an additive for upgrading lower-grade bitumen to higher-grade bitumen. The different colorless polyesters were synthesized using polycondensation of P and G as a monomer in the ratio of 1:1 and polymerization time of 1, 3, 5, and 7 h. A rheological analysis was performed on all the synthesized polyesters to check their performance with respect to their use in bitumen modification. The polyesters were blended with base bitumens (VG10) to obtain the modified bitumens that were tested for the rheological and physicochemical properties and to assess the performance based on the grade quality test. The quality test of the modified bitumens includes softening point (SP), penetration (PEN), kinematic viscosity (KV), dynamic viscosity (DV), and rheological properties as per standard ASTM test methods. Based on the performance evaluation, P1G1H3 polyester was found suitable for blending with bitumen, and further study was carried out with blending of P1G1H3 with 3, 6, 10, and 15 wt%. The finding illustrates that 6.0 wt% of polyester-modified bitumen show an enhanced SP, KV, and DV by 23.6, 86, and 30%, respectively, while decreasing the PEN by 49% with respect to VG10. Polyester blending also improved the rheological parameters in terms of deformation resistance, load-bearing capacity, and the viscoelastic nature of bitumen. The investigation concluded that 6 wt% P1G1H3 polyester on blending in VG10 meets VG30 bitumen specification as per IS:73:2013. synthesis of polyesters and its application in upgrading the lower grade bitumen to higher grade bitumen image