Foaming Behavior of Radiation-Crosslinked Virgin and Recycled Low-Density Polyethylene

Abstract

The increasing demand for sustainable materials has underscored the importance of utilizing polymer waste in various applications. Despite the growing interest in using polyethylene waste for foam production, concerns regarding the mechanical properties of recycled foams present challenges to their reuse, as these properties are critical for foam performance. The mechanical characteristics of foams are closely linked to their cell structure. This study investigates the foaming behavior of irradiated crosslinked virgin and recycled low-density polyethylene by comparing parameters of foam’s cell structure, including foaming degree, cell size distribution, cell density, volume expansion ratio, and foaming rate on a batch scale. Polyethylene foams were produced by melt mixing polyethylene with azodicarbonamide (ADCA) as a blowing agent, followed by irradiation and hot pressing for foaming. The analysis of the produced foams focused on gel content and structural, thermal, and mechanical properties. Results indicate that an absorbed dose of 50 kGy optimizes both virgin and recycled foams, enhancing their expansion and mechanical stability. At this dosage, both types exhibit a closed microcellular structure with a maximum cell density of 10⁵ cells/cm³. The results reveal that while tensile strength decreases with increasing absorbed doses, elongation at break significantly increases. This indicates that recycled polyethylene foams offer enhanced flexibility despite the reduced strength, making them advantageous for applications requiring deformation resistance without failure.