Date of Award

12-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Automotive Engineering

Committee Member

Dr. Srikanth Pilla, Committee Chair

Committee Member

Dr. Beshah Ayalew, Co-Chair

Committee Member

Dr. Igor Luzinov

Committee Member

Dr. Philip Brown

Abstract

Amidst growing concerns about environmental sustainability, the renewed push towards adoption of circular economy has increased focus among several manufacturing sectors on using renewable resources and improving process efficiencies. From the materials standpoint, use of bio-based polymers and natural fibers as sustainable reinforcements are increasingly gaining market share. However, conventional processing methods for fiber reinforced composites are usually energy-intensive and often involve long processing times, which may lead to detrimental environmental impacts. In this context, a holistic attainment of sustainability makes it imperative to adapt sustainable practices not only for raw materials but at every stage of the product. Hence, this work explores, for the first time, the potential power of photons for sustainable processing of natural fiber-reinforced bio-polymer composites. To select a more sustainable matrix material, a comprehensive life-cycle assessment of existing bio-epoxies was carried out. The assessment demonstrated that triglyceride-based epoxies possess the potential to be highly sustainable epoxies if their epoxy equivalent weight is reduced to values of conventional Diglycidyl ether of Bisphenol-A. Hence, triglycerides sourced from perilla oil that possess higher functionality were selected and epoxidized. To obtain epoxidized triglyceride with minimal oxirane cleavage, epoxidation kinetics was systematically studied, and optimal synthesis conditions were determined. A pseudo two-phase model was developed that would demonstrate the variation in reactivity of individual double bonds based on their position as the reaction proceeds. Synthesized epoxidized perilla oil exhibited epoxy equivalent weight of ~164 g/eq which was comparable to Diglycidyl ether of Bisphenol-A. Photo-curing was explored as potential sustainable manufacturing technique due to its fast cure; however, UV attenuation is a major hurdle in curing thicker parts (> 1 mm). Since free-radical mechanism was traditionally studied in photo-cure literature, acrylated epoxidized triglyceride was selected to cure thicker parts. Initially, cure kinetics was studied via photo-calorimetry and appropriate process parameters were selected to cure acrylated triglyceride. In order to process natural fiber-reinforced composite, three different natural fibers, possessing diversified composition of cellulose, hemi-cellulose and lignin content, were selected to understand the effect of fiber constituent on photo-curability. Acrylated epoxidized soybean oil was chosen as matrix material and processed via both thermal- and photo-curing, and their thermal and mechanical performance was evaluated. Photo-curability of natural fiber-reinforced composites was demonstrated for the first time.

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