Dissertation
CHEMICAL RECYCLING OF FIBER REINFORCED EPOXY COMPOSITES AND DEVELOPMENT OF HIGH-PERFORMANCE RECYCLABLE ALTERNATIVES
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004556
Handle:
https://hdl.handle.net/2376/125306
Abstract
In this research, the recycling method for chemically recycling epoxy-based glass fiber reinforced plastics (GFRP) and carbon fiber reinforced plastics (CFRP) in mild conditions was developed. Zinc acetate aqueous solution was used to recycle GFRP from wind turbine blades. Decomposed polymer matrix (DMP) was yielded after degradation. The recycled GFRP (rGFRP) was reused as fiber reinforcement in thermoplastics composites. Composites with rGFRP exhibited enhanced mechanical tensile and impact properties owing to the reinforcement effect of glass fiber and sufficient interfacial adhesion between fiber and matrix that was compatibilized by DMP. The chemical recycling of CFRP was achieved in acetic acid/zinc acetate hybrid aqueous solution. The decomposed polymer was upcycled as the reactive component to prepare new epoxy. Cured epoxies containing DMP moieties possessed vitrimer features and recyclability in pure water. Reclaimed carbon fiber (rCF), which showed similar tensile properties compared to virgin carbon fiber, was reused as the fiber reinforcement for new composites.
A catalyst-free epoxy vitrimers were prepared with the addition of triethanolamine (TEOA) as the catalytic co-curing agent. Commercial bisphenol A epoxy (DER) was cured with nadic methyl anhydride (NMA) which yields ester linkages in the crosslinked network. Hydroxyl groups in TEOA participated in the crosslinked network, and tertiary amines catalyzed the curing as well as dynamic bond exchange reaction. High glass transition temperature (Tg) and mechanical properties were exhibited by cured vitrimer materials, and fast stress relaxation and repairability were also observed. Epoxy vitrimers were recycled by physically grinding or chemically decomposing in aqueous catalyst solution. The recyclates were mixed with fresh epoxy to prepare new epoxy resin, and cured materials showed similar Tg and mechanical properties.
Following the previous vitrimer system, tetraglycidyl methylenedianiline (TGDDM) was chosen to cure with NMA and TEOA. Cured epoxy vitrimer exhibited extremely high Tg (200 °C). Recyclable CFRP was fabricated with high Tg epoxy vitrimers as matrix, and the hydrothermal recyclability was accomplished, that the build-in tertiary amines catalyzed the hydrolysis of ester bonds. Moreover, the decomposed polymer was upcycled to endow recyclability to commercial epoxies, and recycled carbon fiber showed an excellent reinforcement effect in new composites.
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Details
- Title
- CHEMICAL RECYCLING OF FIBER REINFORCED EPOXY COMPOSITES AND DEVELOPMENT OF HIGH-PERFORMANCE RECYCLABLE ALTERNATIVES
- Creators
- Cheng Hao
- Contributors
- Jinwen Zhang (Advisor)Qiang Zhang (Committee Member)Kuen-Ren Chen (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Mechanical and Materials Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 252
- Identifiers
- 99900898639601842
- Language
- English
- Resource Type
- Dissertation