Controlled surface acetylation of cellulosics to tune biodegradability – expanding their use towards conventional plastics

The European Commission's single-use plastics directive has put major restrictions on the use of chemically modified cellulosics for different material applications, e.g., as films, fibres, foams and other shaped objects. In addition, the wet strength and barrier properties of some of these materials are lacking, in comparison to petrochemical-based plastic materials. In the current study we demonstrate that it is possible to carry out surface selective acetylation of kraft fibre paper and nano-paper to create materials that maintain biodegradability. This is shown to be highly dependent on the degree of bulk acetylation, with those materials with modification restricted to fibril surface monoacetylation offering fine control over enzymatic digestibility. Materials which show the formation of cellulose triacetate were much less degradable in the timeframe of our assessment methods. However, the wet strength and extensibility of these materials was significantly improved, pushing the envelope for application towards moisture-rich environments. The mechanistic component of our study shows acetylation occurs down to the elementary fibril surface level, and not just on the macrofibre, or fibrillar bundle, level. We believe that this study offers a strong basis for widening the application scope of cellulosics towards traditionally petrochemical-based synthetic plastics.