Transesterification-vulcanization route to durable composites from post-consumer poly(ethylene terephthalate), terpenoids, and industrial waste sulfur

Abstract

Despite improvements in chemical recycling, most post-consumer plastics are still deposited in landfills where they pose a significant threat to ecological health. Herein we report a two-stage method for chemically recycling poly(ethylene terephthalate) (PET) using terpenoids and waste sulfur to yield composites. In this method, post-consumer PET (from beverage bottles) undergoes transesterification with a terpenoid alcohol (citronellol or geraniol) to yield low-molecular PET oligomers. The terpene-derived alkenes in these PET oligomer derivatives then served as reaction sites for inverse vulcanization with 90 wt% elemental sulfur to form composite CPS (using citronellol) or GPS (using geraniol). Composition, mechanical, thermal, and morphological properties were characterized by NMR spectroscopy, MALDI, FT-IR spectroscopy, compressive and flexural strength analysis, TGA, DSC, elemental analysis, and SEM/EDX. The composites CPS (compressive strength = 5.20 MPa, flexural strength = 3.10 MPa) and GPS (compressive strength = 5.8 MPa, flexural strength = 2.77 MPa) showed mechanical strengths comparable to those of commercial bricks (classification C62 for general building). The approach delineated herein thus represents a method to chemically recycle waste plastic with industrial waste sulfur and plant-derived terpenoids to yield composites having favorable properties comparable to existing building materials.