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

生物塑料包括可堆肥和/或由可再生资源制成的热塑性聚合物，如聚乳酸（PLA）、聚3-羟基烷酸酯（pha）和淀粉基材料。在环境问题、废物处理挑战和石油产品供应问题的推动下，生物塑料的生产出现了爆炸式增长。在工程应用中广泛接受生物塑料的主要挑战是其高生产成本，脆性，缓慢的结晶速率和低熔体强度，这些都限制了其在普通聚合物加工操作下的可加工性。它们相对较差的工程性能限制了它们在相对低价值的消费品中的应用。因此，提高生物聚合物的性能以使其性能与石油基聚合物相匹配是一个非常活跃的研究领域。目前的研究项目将实施简单的共混和无溶剂反应改性工艺，以提高含有聚乳酸和pha的生物聚酯化合物的结晶速率、加工性和性能。我们在小规模的初步研究表明，这种方法可以显著改善聚乳酸的结晶行为和熔体强度。拟议的项目得到加拿大杜邦公司的支持，旨在更大规模地优化和开发这些工艺，确定所产生产品的特性，并进一步寻求在商业工艺和产品中的应用。具体目标包括生产足够数量的PHA，适合大规模复合使用；过氧化引发剂和助剂的种类和用量的优化及适宜的工艺条件的确定；扩大工艺规模，以生产足够数量的产品，以进行全面的特性表征；并与合适的基准材料进行对比。预期的结果是开发一种经济可行、无溶剂、环保的工艺，以获得具有良好工程性能的全生物基产品。申请资助一名硕士生，并为PDF和研究助理提供部分支持。

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.