Effect of Waste Polyethylene and Wax-Based Additives on Bitumen Performance

Driving selective upcycling of mixed polyethylene waste with table salt

Advanced recycling offers a unique opportunity for the circular economy, especially for mixed and contaminated plastics that are difficult to recycle mechanically. However, advanced recycling has barriers such as poor selectivity, contaminant sensitivity, and the need for expensive catalysts. Reported herein is a simple yet scalable methodology for converting mixed polyethylene (high-density and low-density polyethylene recycled polyethylene) into upcycled waxes with up to 94% yield. This high yield was possible by performing the reaction at a mild temperature and was enabled by using inexpensive and reusable table salt. Without table salt, in otherwise identical conditions, the plastic remained essentially undegraded. These upcycled waxes were used as prototypes for applications such as water- and oil-resistant paper, as well as rheology modifiers for plastics. Their performance is similar to that of commercial wax as well as rheology modifiers. A preliminary economic analysis shows that the upcycled waxes obtained by this table salt-catalyzed approach offer three times more revenue than those reported in the literature. This pioneering discovery opens the door for a circular economy of plastics in general and polyolefins in particular.

Evaluating Effectiveness of Multi-Component Waste Plastic Bags on Bitumen Properties: Physical, Rheological, and Aging

This study examines the applicability of an unknown composition waste plastic bag sample as bitumen modifier. The waste components were initially characterized to identify the type of plastics and the level of impurity. Asphalt binder performance was examined for rutting, thermal, and age resistance. The results revealed that the waste plastic bags, predominantly consisted of Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE) and contained 6.1% impurities. The binder tests indicated that the waste plastic bags enhanced the rutting resistance of bitumen by one grade, with its modification more similar to LLDPE, rather than LDPE. The thermal degradation and aging properties of the modified binders demonstrated that the bitumen modified by the waste plastic bags exhibited slightly lower resistance to temperature and aging compared to virgin LDPE and LLDPE. This was attributed to the impurities contained in the waste plastic. In conclusion, the analyzed waste plastic bags proved to be suitable for use in binder modification, presenting a viable alternative to virgin LLDPE.

Radiation and Radical Grafting Compatibilization of Polymers for Improved Bituminous Binders-A Review

This review scrutinizes current research on new methods for enhancing bituminous binder performance through radiation and radical grafting of polymer modifiers of bitumen. It investigates innovative methods, including using waste polymers as modifiers and applying radiation for polymer grafting, to overcome challenges like high costs, low aging resistance, and storage stability issues, of which separation of phases polymer/bitumen is the most significant obstacle. These advanced modification techniques promise sustainability through the decrease of the carbon footprint of transportation systems by improving the properties and durability of binders. Additionally, this review discusses the parameters and mechanistic aspects from a scientific perspective, shedding light on the underlying processes that contribute to the improved performance of modified bituminous binders.

Using Plastic Waste in a Circular Economy Approach to Improve the Properties of Bituminous Binders

This work aims to use wax to modify a binder employed in the paving industry. This wax can be obtained either directly or as a by-product from plastic waste′s thermal cracking (pyrolysis). The study characterizes this sustainable material and the binders resulting from blending it with conventional or modified bitumen with other additives applied in the manufacture of bituminous mixtures. Different tests were used: thermogravimetric and spectroscopic analysis; consistency tests; testing of dynamic viscosity at various temperatures; and assessment of the rheologic properties of binders. As a result, several crucial findings were reached: this sustainable wax promotes changes in the viscosity of the binders, their handling temperatures can be reduced, and it contributes to some goals of the U.N. 2030 Agenda. In summary, this work allowed us to conclude that the positive effects of a suitable modification of the bituminous binders, which incorporated this wax and other additives, led to improved consistency and rheological behaviour, having provided, for example, lower temperature susceptibility and higher permanent deformation resistance.