Solvent Absorption and Dissolution Kinetics Modelling for the Chemical Recycling of Waste Plastic Laminates

Abstract

The Philippines is expected to have an increase in consumption of waste plastic laminates known as sachets, composed of polyethylene (PE) and polyethylene terephthalate (PET) and used in various food and non-food consumer goods. The increase in demand of these sachets has led the country to become one of the top ocean polluters worldwide. Chemical recycling- specifically selective dissolution and reprecipitation- is seen as one viable option for the recovery of these polymers. In this study, the absorption and dissolution kinetics of D-limonene, a potential candidate solvent, in the two-layer (2LL) and three-layer (3LL) laminates were modelled and analyzed for the design of separation equipment to recovery PE. The absorption of limonene for both laminates was observed to initially follow Fickian diffusion, but plateaus when the dissolution rate becomes comparable with the solvent diffusion rate. The dissolution of the 3LL almost closely follows Fickian behavior, while 2LL initially follows Fickian behavior. Deviations from Fickian dissolution may be attributed to the difference in swelling behavior between the non-uniform solvent-polymer diffusion layer and the glassy polymer layer.