Hybrid polyol-based polyurethane from pine merkusii resin and polyethylene glycol 400 for sustainable asphalt modification

• PMR polyol was synthesized using formic acid and hydrogen peroxide at 40 °C, followed by separation and purification to obtain a high-purity polyol. • Hybrid polyol-based polyurethane was prepared by mixing PMR polyol, PEG-400, and toluene-2,4-diisocyanate at 40 °C, forming a crosslinked structure. • Asphalt modification was performed by incorporating hybrid polyol-based polyurethane into asphalt at 180 °C and 1000 rpm, enhancing thermal stability and structural uniformity. Biopolymer-based materials have garnered significant attention as sustainable alternatives for asphalt modification. This interest stems from their ability to improve performance while reducing environmental impact. Conventional asphalt suffers from thermal susceptibility and aging, requiring modifications to enhance durability. Polyurethane-based modifiers, synthesized from polyols, have emerged as promising solutions due to their superior mechanical and thermal properties. This study reports synthesizing and characterizing hybrid polyol-based polyurethane using Pine Merkusii Resin (PMR) as a natural polyol and polyethylene glycol 400 (PEG-400) as a synthetic polyol for sustainable asphalt modification. The research involved three stages: (1) PMR polyol synthesis via oxidation using formic acid and hydrogen peroxide, (2) polyurethane preparation through the reaction of PMR polyol, PEG-400, and toluene-2,4-diisocyanate (TDI), and (3) asphalt modification using the synthesized polyurethane. Comprehensive characterization was performed using GC–MS, FTIR, swelling tests, DSR, TGA, and SEM. GC–MS confirmed the presence of α-pinene and β-pinene in PMR polyol, indicating a high hydroxyl content. The optimal polyurethane formulation (PMR polyol: PEG-400 polyol: TDI at 35.2:8.8:56) showed the highest crosslinking density and the lowest swelling index (5.69 %). FTIR analysis identified urethane network formation at 1630–1680 cm −1 . Rheological tests revealed that asphalt–polyurethane exhibited superior resistance to rutting and cracking under heavy loads and extreme temperatures compared to conventional asphalt. The asphalt–polyurethane blend (80:20) demonstrated the highest onset temperature (459.7 °C) and the slowest degradation rate, indicating excellent thermal stability. FTIR confirmed that polyurethane was well incorporated into the asphalt matrix, while SEM showed uniform dispersion and improved structural integrity. These results highlight the potential of hybrid polyol-based polyurethane as an eco-friendly and durable asphalt modifier.