Full text
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| Author(s): |
Henrique Cesar Pereira Coelho
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Lorena. |
| Institution: | Universidade de São Paulo (USP). Ciência e Engenharia dos Materiais (IFS/EES) |
| Defense date: | 2024-08-05 |
| Examining board members: |
André Luis Ferraz;
Demetrio Jackson dos Santos;
Clodoaldo Saron
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| Advisor: | André Luis Ferraz |
| Abstract | |
Bisphenol A diglycidyl ethers are the most commercially used epoxy resins, covering around 75% of the global market. Although they have proper thermal and mechanical properties, bisphenol A resins show problems related to environmental impacts and human health. Based on this issue, this work aimed to the synthesis of epoxy resins from vanillyl alcohol and lignosulfonates, both compounds derived from lignocellulosic biomass. The first stage consisted of the polymerization of pure vanillyl alcohol or mixtures of vanillyl alcohol and sugarcane or coniferous lignosulfonates through enzymatic oxidation or condensation in acidic medium reactions, in order to obtain polyphenolic products suitable for the synthesis of polyglycidic ethers. From the oxidized or condensed materials, the second stage involved testing these with epichlorohydrin. Finally, in the third step, the resulting epoxy resins were crosslinked with triethylenetetramine, and the crosslinked products were tested for adhesion on Pinus spp. wood surfaces. It was found that the enzymatic oxidation reactions generate products with a content of phenolic hydroxyls lower than the contents of the original substrates, while condensation in an acidic medium preserved the phenolic hydroxyls, with the content being elevated due to the loss of mass due to dehydration. This resulted in considerable differences in equivalent epoxy values, which were greater for acidic conditions, since glycidyl ethers are formed through the etherification of phenols with epichlorohydrin. The resins crosslinked with triethylenetetramine formed materials with glassy characteristics, but direct crosslinking of the resins on wooden surfaces proved to be inadequate due to low penetration into the wood pores. The use of acetone as a non-reactive diluent led to more consistent adhesion, with the resins synthesized from condensation in an acid medium showing resistance greater than the internal resistance of wood when subjected to high pressure, while the resins synthesized from oxidation enzyme presented lower resistance than wood. This can be explained by the difference in epoxy values, which, as they are lower in enzymatic oxidation reactions, should result in resins with lower crosslinking density. (AU) | |
| FAPESP's process: | 22/09174-0 - Enzymatic oxidation and reticulation of lignin/lignosulfonates with phenolic compounds for epoxy resins production |
| Grantee: | Henrique César Pereira Coelho |
| Support Opportunities: | Scholarships in Brazil - Master |