LEGO's Strategy to Upcycle Waste Polyethylene into High-Performance Materials

This dynamically cross-linked multi-functional material exhibits excellent mechanical properties and solvent resistance. Its tensile strength can reach 27 MPa, almost four times that of original PE. Meanwhile, it shows low swelling and mass loss rates in most solvents.

This flame retardant/UV resistant material exhibits a limiting oxygen index of up to 27%, enabling self-extinguishment in air. The peak heat release rate is reduced by up to 73% compared to virgin PE. The formation of flammable small olefin molecules is significantly suppressed during thermal decomposition, and the charring ability is significantly enhanced, achieving a residual mass of up to 33% at 700°C. A stable char layer can form during combustion, providing thermal and oxygen insulation. Furthermore, this material achieves full-band UV shielding.

The surface and volume resistivities of the obtained antistatic/dyeable material were reduced by 2-3 orders of magnitude compared to original PE, meeting the standard for static dissipative materials. The material can be dyed deep blue with methylene blue solution, exhibiting good color fastness, with no dye bleeding. Different colors can be achieved by adjusting the concentration or type of the dye solution.

Due to the inherent lack of reactive functional groups in PE, its functionalization is typically achieved through blending with functional fillers, which leads to significant polarity differences, poor compatibility, and decreased mechanical properties after blending modification. This degradable dynamic crosslinking reconstruction method not only enables modular construction of multifunctional materials but also significantly enhances the mechanical properties of the materials.

Based on the dynamic nature of imine bonds under thermal stimulation and their ability to dissociate in acidic organic solutions, materials can be physically recycled through multiple thermal processes or chemically recovered through complete degradation under acidic conditions.

In summary, this work adopts a "Lego" strategy to transform waste PE into high-performance, multi-functional, and recyclable new materials, achieving a recycling process that upgrades "waste plastics" into "high-value materials." This strategy boasts high flexibility, allowing for further functionalization based on specific needs, and provides new insights for the functional modification and high-value recycling of polyolefin plastics.

The study was recently published in the [Journal Name]. CCS Chemistrypublished in the journal "==". Shen Chengfeng, a doctoral student at Sichuan University, is the first author of this article, and Professor Xu Shimei and Wang Yuzhong The academician is the corresponding author. This research was supported by the National Natural Science Foundation of China.