Degree Type

Thesis

Date of Award

2020

Degree Name

Doctor of Philosophy

Department

Agricultural and Biosystems Engineering

Major

Agricultural and Biosystems Engineering

First Advisor

David Grewell

Abstract

In response to environment and sustainability issues, the materials science field has shown a growth and increasing interest in natural fiber biocomposites as an alternative to synthetic fillers such as glass fibers and talc powder. Albeit many years of research, the greatest challenge with working with natural fiber reinforced plastic composites is their large variation in properties and characteristics as well often required pretreatment and cleaning. These issues have limited the commercial products produced from natural fiber composites. In more detail, natural fiber composite properties are variable and influenced by many parameters such as fiber type, growing conditions, processing methods, and any modification of the fiber. Additional challenge of incorporating natural fibers arises when agricultural byproduct is looked into as a potential source of natural filler because fiber pretreatment to remove impurities has to be taken into consideration before processing. Currently, there is an existing market for agave fiber bagasse and thermoplastic biocomposites in the automotive industry with potential interior applications for storage bins, coin trays, battery and fuse cover, to name a few.

This research aimed develop a technology that would enable commercialization of agave fiber bagasse plastic composites, and to optimize the interfacial adhesion to improve the mechanical properties of these composites for structural application. The research is initially studied hybrid fibers (cellulose and glass) to investigate the properties of recycled polyamide-6 (rPA6) and recycled polypropylene (rPP) blends and served as a baseline for performance specifications, such as specific strength. While adding glass fiber alone enhanced the mechanical properties, incorporation of cellulose fibers into the composite enables use less glass fibers while retaining similar mechanical (small loss) properties which correlated to a weight reduction. However, the addition of cellulose fibers increased the composites stiffness and rPA6/rPP composites were optimized at loading levels of 15 wt.% glass and 10 wt.% cellulose fibers. These properties from the research findings were considered as a baseline performance target of the automotive industry requirements while creating eco-friendly composites in automobile industry.

Biobased composite with polypropylene and agave fiber filler at different loading levels (0-40 wt.%) were investigated. Surface treatments studies on natural fibers to maximize the bonding strength as well as the stress transferability in the composites were also conducted. Treatments using chemicals such as sodium hydroxide, sodium chlorite and acetylation were carried out to improve the bonding at the fiber polymer interface. All the treatments significantly enhanced the tensile and stiffness properties of the composites compared to the control sample (no treatment), but to varying degrees. Among the various treatments, acetylation treatment of fiber reported maximum interfacial interactions.

To further investigate the potential of compounding agave fiber biocomposites, talc-filled thermoplastic olefin (TPO), a polymer matrix commonly used in the automotive industry was studied. The composites were prepared with three different compatibilizers and their thermomechanical, morphological, and water absorption properties were characterized. The compatibilizers had significant improvement on the tensile, flexural strengths, and water absorption; however, no considerable effect on impact strength, elastic or flexural moduli was observed. The composite comprised of TPO, Washington Penn Plastic (WPP) compatibilizer, and agave fibers exhibited the best mechanical properties. The addition of agave fiber increased the elastic and flexural moduli but reduced the elongation to failure and impact strength. Overall, average TPO-agave fiber biocomposites exhibited comparable mechanical properties to pristine TPO and its components as used in automotive industry, while offering environmental and economic advantages.

Talc-filled thermoplastic olefin (TPO) reinforced with agave fiber composites were prepared with three different compatibilizers and their thermal-mechanical, morphological, and water absorption properties were characterized. The objective of this study was to investigate the use of agave fibers as a reinforcing agent in TPO composites. The effects of addition of 20 wt.% agave fiber and compatibilizers (WPP, Adicco 9320, and maleic anhydride grafted polypropylene, PPgMA) on the properties of the TPO- agave fiber composites were comparatively studied. The compatibilizers had a significant improvement on the tensile, flexural strengths, and water absorption; however, no considerable effect on impact strength, elastic or flexural moduli was observed. The composite comprised of TPO, WPP, and agave fibers exhibited the best mechanical properties. The addition of agave fiber increased the elastic and flexural moduli but reduced the elongation and impact strength. Overall, average TPO-agave fiber biocomposites exhibited comparable mechanical properties to pristine TPO and its components as used in automotive industry, while offering environmental and economic advantages.

Because the renewable resources used in this study are agricultural byproducts, pretreatment of the fibers was necessary to remove sugars and impurities that could be damaging to the processing equipment. Traditional washing, a commonly used method for agave fiber bagasse conditioning uses a large amount of resources such as water, time and energy. Ultrasonication experiments in batch-scale were conducted to test the feasibility of potentially substituting the washing method. The results showed that the optimum ultrasound pretreatment conditions for maximum reducing sugar yield was an amplitude of 160 µm for 7.5 min of treatment at 23 °C. Under these conditions, 100% of maximum sugar removal through washing was achieved. Improvement in thermal properties is also observed for ultrasound-treated agave fibers. The substantial reduction in pretreatment time, temperature, energy with improved efficiency is the most attractive features of the ultrasound pretreatment.

DOI

https://doi.org/10.31274/etd-20200624-240

Copyright Owner

Cindu Annandarajah

Language

en

File Format

application/pdf

File Size

164 pages

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