The overall objective of the project is to produce films from hemicellulose, which may potentially be used as food packaging materials. Composite films from hemicellulose and nanoscale fillers will be produced in parallel to films from chemically modified hemicelluloses. Improvement in barrier and mechanical properties relative to native hemicellulose film will be the target.
Although hemicelluloses are very abundant in nature, constituting 20-30% of perennial and annual plants, they are as yet of very limited commercial importance. Hemicelluloses are hygroscopic and when cast from aqueous solutions form brittle and unmanageable films. The challenge is therefore to use physical or chemical means to modify hemicelluloses so that practical uses in the form of films (e.g., for a wide range of packaging applications) might become viable.
In the current project we propose two hemicellulose modification routes:
- Addition of nanofillers to improve the mechanical and barrier properties
- Chemical modification of the hemicelluloses to increase hydrophobicity and to potentially introduce melt processability.
We plan to explore two types of nanofiller, microfibrillated cellulose (MFC) and nano-scale inorganics (e.g., clays). The concept of polymer property enhancement through nano-scale reinforcement is well established, but has not been investigated in any depth with regard to hemicelluloses as the matrix. MFC (also sometimes referred to as nanocellulose) offers unique possibilities as a reinforcing material due to its biodegradability, biocompatibility, fine scale, high stiffness and strength and its availability from various plant resources. The use of inorganic nanoparticles for reinforcing hemicellulose films is also relatively unexplored, but a wide range of both modified and unmodified inorganic nanofillers are commercially available and will be studied within the project.
The literature shows that chemical modification of hemicelluloses has been previously studied and our published review of the literature from 2008 will act as a platform for further investigations. In addition to property enhancements, if melt processability can be demonstrated, a variety of exciting new applications might be opened up. The project plans include the study of monomeric and polymeric alkenyl succinic anhydrides (ASAs) as hemicellulose modifiers, which will be investigated in both conventional and ionic liquids. The latter are a range of “green” solvents, which have high stability and low vapour pressure and in principle may be recycled indefinitely. ASAs are of interest, because they are available commercially in large quantities and already used in the paper industry for the modification of cellulose fibres (sizing process), which leads to reduced water penetration of water in the formed paper.
Significance for future research
Findings from this research project will indicate potential future directions in use of hemicelluloses and will clarify the advantages to be gained by pursuing nanocomposite materials. Specific routes for chemically modifying hemicelluloses in order to make them amenable to melt processing may open up new products and new research pathways directed at competitive, sustainable bio-derived materials.
This project is funded by the Research Council for Technology and Production Sciences (FTP, Forskningsrådet for Teknologi og Produktion, 274-08-0325)
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