Improvement of melt strength and crystallization kinetics of biopolyesters by reactive extrusion

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Bioplastics include thermoplastic polymers that are compostable and/or made from renewable resources, such as poly(lactic acid) (PLA), poly-3-(hydroxyalkanoates) (PHAs), and starch-based materials. The production of bioplastics has seen explosive growth driven by environmental concerns, waste disposal challenges and problems with the supply of petroleum products. Among the key challenges associated with more wide-spread acceptance of bioplastics in engineering applications are their high production costs, brittle nature, slow crystallization rates and low melt strength, which restrict their processability under common polymer processing operations. Their relatively poor engineering properties have limited their applications to relatively low-value, consumer goods. Upgrading the properties of biopolymers to match their performance to that of petroleum-based polymers is therefore an extremely active area of research. The present research project will implement simple blending and solvent-free reactive modification processes to improve the crystallization rates, processability and properties of biopolyester compounds, containing PLA and PHAs. Our preliminary investigations on a small scale have revealed that this approach can result in significant improvements in the crystallization behaviour and melt strength of PLA. The proposed project, supported by E.I. du Pont Canada, aims to optimize and develop these processes on a larger scale, to characterize the resulting products and to further seek applications in commercial processes and products. Specific objectives include the production of sufficient amounts of PHA suitable for use in large-scale compounding; the optimization of the type and amount of peroxide initiator and coagents and the identification of appropriate processing conditions; scale-up of the process to produce sufficient quantities for full property characterization; and comparison with appropriate benchmark materials. The expected outcome is the development of an economically viable, solvent-free, environmentally friendly process to obtain fully bio-based products, with good engineering properties. Funding is requested for a Master's student, and partial support for a PDF and a research assistant.