Insights into constituent interactions in hybrid bitumen systems compatibilized by functionalized polyolefins

• Functionalized Polypropylene (FPP) alters SARA distribution of bitumen. • FPP disperses asphaltenes and compatibilizes Crumb Rubber (CR) in bitumen mixtures. • In CR-modified bitumen, FPP improves CR dispersion by physicochemical interactions. • FPP enhances CR-bitumen compatibility, aiding rubber digestion & network formation. • Chemical IR shifts show FPP-driven changes, boosting binder’s properties. The incorporation of greater amounts of crumb rubber (CR, >5 wt%) into bitumen formulations is hindered by the phase separation, processing difficulties, and insufficient ductility of crumb rubber modified bitumen (CRMB). Our previous studies on in-reactor-functionalized polyolefins, specifically poly(propylene- co -hex-1-ene- co -hex-5-en-1-ol) (FPP), have demonstrated their good compatibility with CRMB. This enabled the incorporation of up to 10 wt% CR while maintaining good processability, improving stability during storage and transportation, as well as functional performance characteristics i.e. low-temperature ductility. To further investigate the mechanisms behind the compatibility and aging of systems containing FPP and CR, a systematic compositional study was undertaken. The findings on the effects of RTFO oxidative aging and thermal degradation by TGA indicate that the addition of FPP improved the thermal stability and anti-aging resistance of CRMB. The amphiphilic nature of FPP shifted the polarity gradient within the bitumen matrix, which was confirmed by a lower content of asphaltenes through TLC-FID. Mixing FPP terpolymer with neat bitumen did not induce noticeable composition changes compared to the control sample. Built upon the morphology and ATR-FTIR studies of the FPP-compatibilized hybrid systems and phases separated thereof via Soxhlet extraction, there are evident enhanced interactions between CR, FPP, and bitumen constituents.