Assessing the Impact of Low-Density Polyethylene on Binder Modification and Rheological Performance: Effect of Plastic Source Variability

Abstract

This research study evaluates the effect of four different sources of waste low-density polyethylene (LDPE) on the rheological performance of plastic-modified binders. LDPE is widely used in packaging, primarily as a single-use plastic, and because of its low economic value after recycling, it holds the largest share among the non-recycled plastic waste. The optimum plastic source was identified using a multi-criteria decision-making (MCDM) approach based on eight different parameters. The findings indicate that the melt flow index (MFI) and degree of crystallinity (DOC) are the most sensitive parameters to variations in plastic sources. Binder modification with plastics reduces the J_{nr 3.2} values by 58.6%, 60%, 60%, and 70% at 60°C for LDP, LDF, LDS, and LDPU, respectively, compared with the base binder. Conversely, recovery values increased by 214, 130, 426, and 486 times for LDP, LDF, LDS, and LDPU, respectively, at 60°C. LDPE sources with higher MFI showed relatively lower mixing time, higher plastic dosages, and improved storage stability. LDPE sources containing functional groups of ketone and aldehyde, resulting from microbial degradation, showed superior processing parameters but lower performance compared with other LDPE sources. Additionally, MFI of polymers exhibited an inverse correlation with fatigue performance at lower temperatures, while DOC had a direct correlation with fatigue life (N_f). The study identifies that both DOC and MFI are crucial in defining the rheological performance of modified binders, especially at high temperatures, although their relative dominance remains undetermined. Overall, the modified binder exhibits improved performance at higher and intermediate service temperatures.