Green and scalable processing of water‐soluble, biodegradable polymer/clay barrier films

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. Hydroxypropyl methylcellulose and alginate are evaluated as candidates to replace poly(vinyl alcohol) in water‐soluble packaging applications with biodegradation in wastewater. By incorporating a collapsed nematic suspension of clay platelets as the inner barrier layer, common setbacks like high processing viscosities, embrittlement, and impedance of biodegradation are avoided. Processing is scalable to roll‐to‐roll systems, and conditions are tunable for application‐specific requirements.