Towards a Better Understanding of Delamination of Multilayer Flexible Packaging Films by Carboxylic Acids

Recycling multilayer plastic packaging is challenging due to its intrinsic compositional heterogeneity. A promising route to increase recycling rates for these materials is delamination, which allows recycling the polymers separately. Yet, this process is not well understood on a fundamental level. This study aimed to obtain first principles-based insights of the delamination mechanism of multilayer flexible packaging film (MFPF) with carboxylic acids. Delamination of MFPFs was described through a model based on Fick's first law of diffusion and first-order dissolution kinetics of polyurethane adhesives. The model was experimentally tested on 5 different MFPFs at different temperatures (50-75 degrees C), formic acid concentrations (50-100 vol %), and solid/liquid (S/L) ratios (0.005, 0.025, and 0.12 g mL(-1)). Under the studied conditions the model proved to successfully estimate the delamination time of MFPF with the average Theil's Inequality Coefficient (TIC) value of 0.14. Essential for scaling-up delamination processes is the possibility to use high S/L ratios as the solubility of the adhesive is rarely limiting.

Automated summary

This study provides insights into the delamination mechanism of multilayer flexible packaging film (MFPF) with carboxylic acids by using a first principles-based approach. The model developed based on Fick's first law of diffusion and first-order dissolution kinetics of polyurethane adhesives successfully estimated delamination time under different experimental conditions. The possibility of using high S/L ratios in scaling up delamination processes is highlighted.