The overall objective of this project is to develop microfibrillated cellulose fibre (MFC) reinforced polylactide (PLA) biopolymer nanocomposites via an industrially practical method. We would like to explore novel ways of combining positive feaures of PLA and MFC and thereby obtain nanocomposite materials with superior properties.
In certain industrial and commercial applications (e.g., packaging, composites, electronic components) there is now increasing interest in replacing synthetic petroleum-derived polymers with renewable and biodegradable materials. Polylactide (PLA) is a biodegradable aliphatic polyester derived from 100% renewable resources such as corn and sugar beets. It is one of the few commercially available biopolymers which has similar properties to fossil fuel-based commodity plastics (e.g., PET,PS). However, PLA also has some shortcomings which restrict its use, such as its inherent brittleness, low thermal stability and relatively high price. Another disadvantage of PLA is that the gas and water vapour barrier properties are not as good as those of the traditional polyolefins. Although a number of approaches have been proposed for improving the properties of PLA (e.g., blending and copolymerization, fibre reinforcement), the preparation of nanocomposites is considered to be one of the most promising methods.
Application of natural nanofibers such as microfibrillated cellulose (MFC) opens the potential for fully degradable and renewable bio-nanocomposites. MFC (also referred as nanocellulose) offers unique possibilities as a reinforcing material due to its fine scale, high stiffness and strength. Moreover it is biodegradable and produced from renewable resources. However, because of its highly hydrophilic nature, MFC cannot be uniformly dispersed in non-polar polymer matrices such as PLA. Improvement of the compatibility of the two materials, therefore requires chemical modification of MFC or other novel methods involving PLA modification. Although the literature reveals that several studies have been performed on this issue, to date there is no practical way to produce MFC nanocomposites based on hydrophobic biopolymers. One practical way to combine the beneficial properties of MFC and PLA might be a lamination of the two materials, which to our knowledge has not been done previously. On the other hand thermoforming of such MFC-PLA laminates could be problematic, which would limit the range of applications. This processing problem could be overcome if MFC-PLA films could be extruded, however, as mentioned already, this would require chemical modification of MFC or PLA.
Project tasks:
Deriving from the overall objective, this project will focus on the following tasks:
- Characterization of MFC films and optimization of film production methods
- Production of PLA by melt extrusion and solution casting and optimization of procedures.
- Introduction of various plasticizers and monitoring their effect on film properties.
- Production and characterization of modified MFC-PLA laminates with different thicknesses.
- Chemical modification to improve the compatibility of MFC and PLA.
- Extrusion and characterization of chemically modified MFC-PLA composites.
Future prospects:
The results of the project will serve as basis for further research. For example, PLA itself could be reinforced with inorganic nanofillers and laminated with MFC. In such a way, the beneficial effects of the nanoclays and nanofibers could be combined, while undesired interference between these different types of nano-reinforcement during compounding could be avoided. This research could therefore open the door to a wide variety of advanced nanocomposite films with even better properties.
This project is funded by the Research Council for Technology and Production Sciences (FTP,Forskningsrådet for Teknologi og Produktion, 274-08-0072)
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