Wood Fiber Polyamide Composites for Automotive Applications
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The automotive industry is currently experiencing environmental, legislative, and consumer pressure to improve the environmental sustainability of passenger vehicles. Just one of the approaches being taken to address this issue is the reconsideration of materials used in automotive application. The purpose of this thesis is to reduce the material weight and increase the environmental sustainability of polyamide composites in automotive parts. Specifically, an objective is to evaluate various types of polyamide and wood fiber blends and compare the mechanical and thermal properties with the intention of replacing glass fiber composite. The lower density of wood fibers could introduce weight savings that would improve fuel efficiency. Two industrial sources of natural wood fiber are considered. These fibers are referred to as Suzano fiber and Woodforce fiber. The primary difference between these fibers is the type of processing. The polyamides compared include PA 6,10, PA 10,10 and recycled PA 6. Additionally, a hybrid blend of 30% PA 6,10 and 70% PA 6 is investigated. Composites are prepared through twin screw extruding and injection molding. The thermal and mechanical properties are measured through TGA, DSC, flexural tests, tensile tests, and Izod impact tests. Due to the high melt temperature of polyamide, one of the main challenges of natural fibers is the thermal degradation that occurs. The use of ultraviolet light treatment is briefly investigated on the wood fibers in consideration, however it determined to be unnecessary for higher cellulose level fibers. In addition to comparing thermal behaviour of composites, alternative options addressing the issues associated with thermal degradation are explored through carbon fiber and odor adjusting additive. Through thermal and mechanical comparisons, it was determined that the Suzano fiber had the highest improvement of mechanical properties when compounded with each polyamide. However, the disadvantage of the Suzano fiber is its ability to feed into the processing equipment. By replacing the Suzano fiber with cellulose, it was determined that overall, the 20% cellulose level resulted in the most favourable combination of properties. The blending of RPA 6 and PA 6,10 generally resulted in intermediate property values however did not offer any significant advantages. The use of PA 6,10 is good for sustainability because of its bio-content but must be balanced with the additional cost.