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Maximilian Röhrl, Renee L. Timmins, Dipannita Ghosh, Dominik D. Schuchardt, Sabine Rosenfeldt, Simon Nürmberger, Uwe Bölz, Seema Agarwal, Josef Breu

Journal of Applied Polymer Science, 2023. https://doi.org/10.1002/app.54418

Poly(vinyl alcohol) (PVOH) based water-soluble packaging with intentional disposal into wastewater provides great convenience for both households and industry. In this paper, we demonstrate with CO₂ evolution testing that only insignificant fractions (~2%) of PVOH biodegrade in wastewater within 33 days. To avoid unintentional environmental build-up and the accompanying consequences to marine life, alternative materials with a suitable balance of performance and biodegradability are needed. Until now, the barrier properties of biodegradable biopolymers could not compete with state-of-the-art water-soluble packaging materials like PVOH films. In this paper, we report on waterborne, sandwich-structured films using hydroxypropyl methylcellulose or alginate produced with an industrially scalable slot-die coater system. The inner layer of the film consists of a collapsed nematic suspension of high aspect ratio synthetic clay nanosheets that act as an impermeable wall. Such a film structure not only allows for barrier filler loadings capable of sufficiently reducing oxygen and water vapor permeability of alginate to 0.063 cm3 mm m⁻² day⁻¹ bar⁻¹ and 53.8 g mm m⁻² day⁻¹ bar⁻¹, respectively, but also provides mechanical reinforcement to the biopolymer films facilitating scalable processing. Moreover, the films disintegrated in water in less than 6 min while rapid biodegradation of the dissolved polymer was observed.