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Biodegradable Polymer Blends and Their Biocomposites: Compatibilization and Performance Evaluation

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Title: Biodegradable Polymer Blends and Their Biocomposites: Compatibilization and Performance Evaluation
Author: Muthuraj, Rajendran
Department: School of Engineering
Program: Engineering
Advisor: Mohanty, Amar Kumar
Abstract: Non-biodegradable polymers, polymer blends and composites are known to persist in the environment over a long time. The use of certain biodegradable polymers is limited as they often fail to match some of the non-biodegradable counterpart perfromances. Blends of biodegradable polymers and composites with complementary attributes can provide materials that strike a balance between cost and performance. This research was focused on the fabrication and performance evaluation of biodegradable polymer blends and composites, as potential alternatives to non-biodegradable polymeric materials. Industrially viable melt processing techniques like extrusion and injection molding were adopted to fabricate and evaluate the structure-property-relationship of biodegradable polymer blends and composites. In this research work, two different types of commercially available biodegradable polyesters, namely poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS) were used to fabricate binary blends and composites. Melt blending these two polymers yielded synergistic properties, which are not present in the respective polymers. The optimal PBS/PBAT blend was selected based on its overall performance and it was used as the standard biocomposite matrix. Miscanthus is a purpose grown energy crop and has not been explored much for polymer composite applications. This fiber was used as reinforcing agents in the PBS, PBAT and blend of PBS/PBAT matrix to compare the effects of matrix properties upon the performance of the resulting composites. One important aspect of this study was reactive compatibilization to improve the interfacial adhesion between the miscanthus fibers and polymer matrix. Maleic anhydride grafted polyesters were synthesized as a compatibilizer, which was used to improve the compatibility with the miscanthus fibers and polymer matrices. The improved fiber-to-polymer matrix adhesion exhibited in better mechanical performances of the resulting composites compared to that of uncompatibilized counterparts. The influence of major processing parameters such as processing temperature, screw speed, fiber length, and holding pressure on the mechanical performance were statistically analyzed by factorial design of experiment. The impact strength of the PBS/PBAT/miscanthus fiber composites was significantly dependent on the fiber length. The durability of the biodegradable polymer (PBS, PBAT and PBS/PBAT blend) was investigated after being exposed to elevated temperature (50oC) and humidity (90%) for 30 days. It was found that the mechanical properties of the samples were heavily affected under the selected environmental conditions and exposure time. An optimum biocomposite formulation was successfully extruded and injection molded for continuous prototype manufacturing in pilot-scale production facilities.
Date: 2015-11
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