Upcycling waste PMMA to durable composites via a transesterification-inverse vulcanization process

Poly(methyl methacrylate) (PMMA) is an important commodity polymer having a wide range of applications. Currently, only about 10% of PMMA is recycled. Herein, a simple two-stage process for the chemical upcycling of PMMA is discussed. In this method PMMA is modified by transesterification with a bio-derived, olefin-bearing terpenoid, geraniol. In the second stage, olefin-derivatized PMMA is reacted with sulfur to form a network composite by an inverse vulcanization mechanism. Inverse vulcanization of PGMA with elemental sulfur (90 wt.%) yielded the durable composite PGMA-S. This composite was characterized by NMR spectrometry, IR spectroscopy, elemental analysis, thermogravimetric analysis, and differential scanning calorimetry. Composite water uptake, compressional strength analysis, flexural strength analysis, tensile strength analysis, and thermal recyclability are presented with comparison to current commercial structural materials. PGMA-S exhibits a similar compressive strength (17.5 MPa) to that of Portland cement. PGMA-S demonstrates an impressive flexural strength of 4.76 MPa which exceeds the flexural strength (>3 MPa) of many commercial ordinary Portland cements. This study provides a way to upcycle waste PMMA through combination with a naturally-occurring olefin and industrial waste sulfur to yield composites having mechanical properties competitive with ecologically detrimental legacy building materials.

Automated summary

This study presents a two-stage chemical upcycling process for Poly(methyl methacrylate) (PMMA). By modifying PMMA with a bio-derived olefin-bearing terpenoid and reacting it with sulfur, a durable composite with mechanical properties competitive with traditional building materials is obtained.