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Open AccessArticle

Thermal Healing, Reshaping and Ecofriendly Recycling of Epoxy Resin Crosslinked with Schiff Base of Vanillin and Hexane-1,6-Diamine

by 1,†, 1,†, 1,* and 2,*
1
Division of Semiconductor and Chemical Engineering, Chonbuk National University, Baekjedaero 567, Deokjin-gu, Jeonju, Chonbuk 54896, Korea
2
Research Center, NEPES AMC, 99 Seokam-ro, Iksan, Chonbuk 54587, Korea
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Polymers 2019, 11(2), 293; https://doi.org/10.3390/polym11020293
Received: 1 February 2019 / Revised: 8 February 2019 / Accepted: 8 February 2019 / Published: 10 February 2019
(This article belongs to the Special Issue Dynamic Chemistry in Polymer Science)
A bio-derived dihydroxylimine hardener, Van2HMDA, for the curing of epoxy resin was prepared from vanillin (Van) and hexamethylene-1,6-diamine (HMDA) by Schiff base formation. The epoxy resin of diglycidyl ether of bisphenol A was cured with Van2HMDA in the presence of the catalyst, 2-ethyl-4-methylimidazole (EMI). The crosslinked epoxy resin showed thermal-healing properties at elevated temperatures. Moreover, the crosslinked epoxy resin can be reshaped by heating via imine metathesis of the hardener units. The imine metathesis of Van2HMDA was confirmed experimentally. Stress-relaxation properties of the epoxy resin crosslinked with Van2HMDA were investigated, and the activation energy obtained from Arrhenius plots of the relaxation times was 44 kJ/mol. The imine bonds in the epoxy polymer matrix did not undergo hydrolysis after immersing in water at room temperature for one week. However, in the presence of acid, the crosslinked polymer was easily decomposed due to the hydrolysis of imine bonds. The hydrolysis of imine bonds was used for the ecofriendly recycling of crosslinked polymer. It is inferred that thermal-healing, reshaping, and reprocessing properties can be implemented in the various crosslinked epoxy resins with the bio-derived dihydroxylimine hardener, albeit the recycled epoxy resin is of inevitably lower quality than the original material. View Full-Text
Keywords: crosslinked epoxy resin; thermal-healing; recycling; imine metathesis; bio-derived hardener crosslinked epoxy resin; thermal-healing; recycling; imine metathesis; bio-derived hardener
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MDPI and ACS Style

Mai, V.-D.; Shin, S.-R.; Lee, D.-S.; Kang, I. Thermal Healing, Reshaping and Ecofriendly Recycling of Epoxy Resin Crosslinked with Schiff Base of Vanillin and Hexane-1,6-Diamine. Polymers 2019, 11, 293.

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