Recyclable polyurethane/nanoclay films

A series of polyurethane (PU)/clay nanocomposite films was prepared by adding natural bentonite Cloisite® Na⁺ powders to waterborne polyurethane dispersions (PUDs) followed by a slow water evaporation; the nanoclay content in the films varied from 0 to 5 wt%. The functional properties of materials with low nanoclay loading (up to 1 wt%) resemble features of films prepared without any nanoclay. Compared to unfilled PU, the films with 3 and 5 wt% nanoclay concentrations exhibited slightly deteriorated properties. This phenomenon can be caused by the fact that the polymer–filler interactions are negligible. Gas transport properties are the exception: nanoclay was found to be an efficient barrier component for the permeability of industrially important gases (O₂, N₂, H₂, CO₂, and CH₄). All films feature thermoplastic characteristics and thermal stabilities up to at least 200°C. Because PUDs are solely composed of linear chains, the possibility of preparing recyclable materials was tested. While PU can be re‐used after dissolving in acetone and re‐dispersing in water, the re‐use of nanoclay is not recommended. Preliminary accelerated in vivo tests performed in 20% H₂O₂ and 0.1M CoCl₂ at 37°C detected substantial susceptibility to biodegradation, especially for films containing 5 wt% nanoclay. POLYM. COMPOS., 40:4079–4092, 2019. © 2019 Society of Plastics Engineers