Understanding the Dissolution Kinetics of a DINCH Plasticized PVC: Experimental Design and Applied Modeling

Polymer dissolution-precipitation recycling is a promising pathway to increase plastic recycling rates. One of the first steps in this process is the dissolution of the plastic, where it is important to understand and predict the dissolution kinetics, specifically for plastic waste. Therefore, the dissolution kinetics of a plasticized poly(vinyl chloride) sample (P-PVC), containing bis(7-methyloctyl) cyclohexane-1,2-dicarboxylate (DINCH), are analyzed in N-methyl-2-pyrrolidinone (NMP), cyclohexanone, methyl ethyl ketone (MEK), and 2-methyltetrahydrofuran (2-MeTHF). Additionally, the effects of the particle size (1090-2990 μm) and temperature (30-60 °C) are studied. As expected, lowering the particle size and increasing the temperature reduced the overall dissolution time. It is also found that the dissolution of the polymer and plasticizer occurred simultaneously, and that the fastest dissolution occurred in NMP, followed by cyclohexanone, MEK, and 2-MeTHF. Finally, both a chain disentanglement model and a first-order model with a diffusion-based rate coefficient are fitted to the experimental data to describe the dissolution behavior of the selected plastic waste. The first is found to be a slightly better description of the P-PVC dissolution profile in NMP, a known good solvent, while the latter is better at describing the dissolution in MEK and 2-MeTHF, the slowest analyzed solvents.