New processing methods for cellulose nanocomposites
Polymer composites based on cellulose nanocrystals (CNCs) have attractive properties that make them interesting materials to work with. So far, however, industrially useful production processes for these materials have been lacking. The research project developed principles for easy fabrication of CNC-based nanocomposites.
Project description (completed research project)
The research project provided the scientific basis for developing easily scalable processes for fabricating nanocomposites comprised of CNCs and technologically relevant plastics. In a first step, the researchers developed processes for fabricating homogeneous blends of both components with the best possible mechanical properties. In a second step, the scientists investigated nanocellulose can be protected from the damage it typically sustains upon exposure to high temperature and shear in conventional melt processing. In a third step, the nanocellulose was equipped with a universal compatibiliser that facilitates blending with different types of plastics.
A wide range of nanocomposites made from different plastics and CNCs have been fabricated in the past. However, up to now it has not been possible scale up their preparation from the laboratory to commercial production scale. As a result, the materials are still technologically of little use and have not yet led to any major industrial applications.
The research project aimed to develop new, scalable and robust methods for producing nanocomposites using technologically relevant plastics and CNCs from wood. This should pave the way to industrial production of CNC materials for the Swiss timber industry.
The insights gained from the project have led to better understanding of the relationship between the processing, structure and properties of CNC/polymer nanocomposites. This should help in developing new fabrication methods and material concepts. Significant progress has been made in all the process steps, which brings industrial production of nanocomposites containing CNCs (e.g. from wood) much closer and paves the way to the industrial production of CNC composites.
The results reveal a relationship between shear forces, CNC degradation and the mechanical properties of the materials. Blending at low shear produced materials which showed optimal mechanical properties, did not degrade well-dispersed CNCs and the composites retained their original morphology. The results of this study were successfully applied in manufacturing nanocomposites based on CNCs and low-density polyethylene (LDPE), polyamide and various polyurethanes. The data show that it is possible to achieve significant mechanical improvement through the use of highly scalable blending processes under low shear.
Processing of polymer/cellulose nanofiber composites