Structure, properties and biodegradability of water resistant regenerated cellulose films coated with polyurethane/benzyl konjac glucomannan semi-IPN coating

We prepared a series of novel water-resistant cellulose films by coating castor oil-based polyurethane (PU)/benzyl konjac glucomannan (B-KGM) semi-interpenetrating polymer networks (semi-IPN) on regenerated cellulose (RC) films, which was obtained from cotton linter in 6 wt% NaOH/5 wt% thiourea aqueous solution by coagulating with 5 wt% H2SO4 aqueous solution. The effect of B-KGM content on interfacial structure, thermal stability, mechanical properties in dry and wet states and biodegradability of the coated films were investigated by Fourier transform infrared spectra, ultraviolet spectroscopy, transmission electron microscopy, dynamic mechanical thermal analysis, tensile test and biodegradation test. The results indicate that PU prepolymer molecules in the semi-IPN coating penetrate simultaneously into the RC film, and give rise to a shared PU network between B-KGM and cellulose. B-KGM in the semi-IPN coating layer plays an important role in enhancement of the mechanical properties, water resistivity, thermal stability, light transmittance of the coated films. The tensile strength of the coated films increases from 86.3 to 114.9 MPa in dry state and from 33.8 to 56.4 MPa in wet state, as well as the light transmittance at 800 nm from 79% to 90% when B-KGM content increases from 0 wt% to 80 wt%. The biodegradation rates of the coated films increase with an increase of B-KGM content and the their biodegradation half-time is less than 80 days. (C) 2004 Published by Elsevier Ltd.