Melt processing of dialcohol cellulose fibres into bulk re-processable materials
E. Pellegrino1,2, G. Lo Re2, A. Fina1
1 Politecnico di Torino, Dipartimento di Scienza Applicata e Tecnologia, viale Teresa Michel 5, 15121 Alessandria, Italy
2 Chalmers University of Technology, Department of Industrial and Materials Science, Rännvägen 2A, 412 58 Göteborg, Sweden
Awareness of the environmental impact of non-biodegradable and fossil-based plastics drives interest in renewable alternatives like cellulose and its derivatives. These materials offer good mechanical properties at relatively low densities due to the strong intermolecular interactions between cellulose chains. However, these interactions also result in a melting point above the degradation temperature of cellulose, precluding conventional thermoplastic manufacturing processes, such as melt-processing.
Cellulose chemical modification into dialcohol cellulose (DAC) fibres reduces cellulose crystallinity, creating a processability window between the decreased glass transition and the degradation temperature. Previous studies demonstrated that DAC can be melt-processed using water in relatively large amounts as a processing aid, yielding a quite rigid material with moisture-sensitive mechanical properties. Aiming at tailoring the thermomechanical and viscoelastic properties of DAC, in this study, a set of less volatile plasticizers (i.e. urea, glycerol, sorbitol, isosorbide) were exploited. Results showed enhancements in the processability and reduction of DAC-based materials inherent sensitivity to external conditions. To further expand the range of thermo-physical properties, DAC was blended with starch, an abundant bio-based and biodegradable polymer, melt-processable in the presence of suitable plasticisers.
This work reports on the melt-processability (assessed by in-line melt viscosity), surface morphology (scanning electron microscopy), thermal stability (thermogravimetric analysis), crystallinity (X-ray diffraction), mechanical properties (tensile tests), viscoelastic behaviour (dynamic thermo-mechanical analysis) and molecular mobility (assessed by dynamic frequency sweep and stress relaxation tests) of the different DAC-based formulation, to discuss achievements and challenges for the exploitation of these fibres.