Isotactic polypropylene (iPP) is the second most produced plastic (nearly 100 million tons/annum). iPP is a semicrystalline thermoplastic, and is typically processed from the melt state into final products. Thermoplastics can be melted and re-processed: therefore, iPP can, in principle, be recycled thermomechanically. However, melt processing takes place at elevated temperatures, typically near 240oC and can result in scission of molecular bonds. This results in deterioration of properties of the plastic.

In this project, the student will systematically investigate the effect of repeated thermomechanical processing on the molecular properties of iPP. The propensity of the recycled iPP to form microplastics, through quiescent oxidative degradation (protocol described in our previous work: https://www.nature.com/articles/s41467-025-58233-3), will be assessed. The influence of mechanical reprocessing on microplastic formation will also be related to the essential work of fracture (https://pubs.as.org/doi/full/10.1021/ma062567r, https://doi.org/10.1016/j.polymertesting.2004.04.013). This project is primarily experimental and the student will be exposed to polymer processing techniques, molecular characterization techniques for polymers (such as rheology, solid property measurements, etc). The student will interpret the results on the basis of fundamentals of polymer science and engineering, particularly polymer physics.