Oxidative Upcycling of Polyolefin Wastes into the Dynamically Cross-Linked Elastomer
Yinlong Chang, Yangke Xiao, Minghao Sun, Wei‐Qiang Gao, Liqian Zhu, Qingyue Wang, Wenjun Wang, Bo‐Geng Li, Pingwei Liu
Abstract
Oxidative cracking of polyolefins into functionalized molecules or oligomers promises the chemical upcycling of plastic wastes. In this work, we develop a novel approach to polyolefin waste upcycling that utilizes low-temperature oxidative cracking combined with dynamic cross-linking to produce recyclable elastomers. High-density polyethylene is oxidized into functionalized oligomers with end carboxyl groups at 110 °C, achieving tunable number-average molecular weights ( M n ) ranging from 1500 to 5500 Da at distributions ( D̵ ) between 2.91 and 3.33. These oligomers with high crystallinity directly react with amorphous cis -polybutadiene containing pendant epoxy groups (an oxidized product of cis -polybutadiene) through esterification, forming a dynamically cross-linked elastomer. The elastomer displays a low glass transition temperature ( T g ) of approximately −100 °C while maintaining a melting point ( T m ) above 80 °C; it showcases a Young′s modulus ( E ) of 12.0 ± 0.4 MPa, elongation at break (ε) of 600 ± 28%, tensile strength (σ) of 16.4 ± 0.8 MPa, tensile toughness ( U T ) of 46.0 ± 3.5 MJ·m –3, and a good elasticity with 81.8% elastic recovery in a 10-cycle tensile test, even higher than that of commercial POEs such as POE-8150 of Dow Company. The dynamic ester-bond-based cross-linking enables the elastomer to be reprocessed. Our study introduces an efficient chemical upcycling process for polyolefin wastes, eliminating the need for tedious separation steps of cracking products.