Transforming Waste Polystyrene into High-Performance Porous Frames with Tunable Cellular Structures via Supercritical Nitrogen Foaming

Due to white pollution-related sustainable development and environmental concerns, it is desirable to recycle the widely used plastic wastes, especially the nondegradable but versatile polystyrene (PS). In this work, the wasted PS particles are converted into a high value-added porous frame with tunable cellular structures via the eco-friendly supercritical nitrogen (scN(2)) extruded foaming technology. Meanwhile, an interesting secondary cell growth phenomenon is found and elaborately explained when adjusting the gap of the rollers during the above process. Besides, the structure-function relationship among solid structures, cellular structures, and the pullout strength of the recycled PS (rPS) is analyzed. Furthermore, in order to optimize the structure design and study the effect of microstructure on its fracture mechanism in the screw pullout testing, three numerical models with different cellular structures are used to illustrate the propagation of cracks within the porous structures. Herein, it is indicated that the secondary cell growth can endow the rPS foams with a higher expansion ratio and open-cell content, but it is not conducive to improving the pullout strength of the materials due to the thin cell walls and low bending capacity. Through the combination of the experimental data and numerical simulation, this work develops a sustainable way to promote the recycling of waste PS into photo frames, mirror frames, decoration line, or other material applications, and provides innovative ideas for their structural design.

Automated summary

This study aims to convert waste polystyrene into a high value-added porous frame using environmentally friendly supercritical nitrogen extruded foaming technology. It also explores the phenomenon of secondary cell growth and its impact on the material's properties. By combining experimental data and numerical simulation, a sustainable method for promoting the recycling of waste polystyrene is developed, providing innovative ideas for structural design.