Abstract
Coffee is a widely consumed beverage, but approximately 80% mass of coffee cherry is discarded as waste. In this study, spent coffee grounds (SCG) were recycled and used as a natural filler in a polyester-based epoxy matrix made from reactions of diglycidyl ethers of Bisphenol A and polyethylene glycol with methyl nadic anhydride. The properties of SCG/epoxy composites with various SCG contents up to 40% w/w were evaluated using various techniques such as FT-IR spectroscopy, tensile testing, optical microscopy, differential scanning calorimetry, and rheology. The SCG filled polyester-based epoxy matrix demonstrated excellent dimensional stability and retained a permanently crosslinked network, but re-shaping was possible at ∼150 °C through transesterification, which occurred due to a dynamic chain exchange reaction between the ester group of the epoxy matrix and the hydroxyl group of the SCG fillers. The transesterification also improved the interfacial adhesion between the matrix and SCG fillers, resulting in tensile strength of over 20 MPa and a modulus of around 2.5 GPa, even with high SCG contents up to 40% w/w. While neat, cured epoxy shows thermoset behavior, filling the matrix with SCG enables reforming and origami-inspired spontaneous change in shape.
Original language | English |
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Article number | 110756 |
Journal | Composites Part B: Engineering |
Volume | 260 |
DOIs | |
State | Published - Jul 1 2023 |
Funding
This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office Program. JS, and AKN acknowledge support from US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division for rheological characterization of vitrimeric materials. This research partly utilized resources of the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility (JKK). The authors would like to express their gratitude to Chris Keum for conducting the analysis of SCG size and distribution through the utilization of the ImageJ software. This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE- AC05-00OR22725 , was sponsored by the Office of Energy Efficiency and Renewable Energy , Vehicle Technologies Office Program. JS, and AKN acknowledge support from US Department of Energy , Office of Science , Basic Energy Sciences , Materials Sciences and Engineering Division for rheological characterization of vitrimeric materials. This research partly utilized resources of the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility (JKK). The authors would like to express their gratitude to Chris Keum for conducting the analysis of SCG size and distribution through the utilization of the ImageJ software.
Keywords
- Composite
- Cyclic anhydride
- Epoxy
- Spent coffee ground
- Transesterification
- Vitrimer