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Applying pH modulation to improve the thermal stability of melamine–formaldehyde microcapsules containing butyl stearate as a phase-change material
ID Alič, Branko (Author), ID Šebenik, Urška (Author), ID Krajnc, Matjaž (Author)

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Abstract
This paper presents a two-stage microencapsulation process that uses pH modulation to enhance the thermal stability of microcapsules that consist of a melamine–formaldehyde (MF) shell and a butyl stearate core. In the first stage, the pH value was modulated between 6.0 and 8.0. Rising the pH value to 8.0 slowed the polycondensation rate, allowing the MF resin with a lower degree of polymerization to migrate to the capsule surface and form a smooth shell. Lowering the pH value to 6.0 accelerated polycondensation. In the second stage, a relatively fast, continuous reduction in the pH value to 5.0 led to further MF polycondensation, hardening the shell. Post-curing at 100 °C prevented shell damage caused by the liquid–gas phase transition of the core material during the process. The microcapsules produced by increasing the pH value to 8.0 twice demonstrated improved thermal stability, with only a minimal overall weight loss of 5% at 300 °C. Significant weight loss was observed between 350 and 400 °C, temperatures at which the methylene bridges in the MF shell undergo thermal degradation. The results from differential scanning calorimetry, electron microscopy, and thermogravimetry analyses confirmed a successful optimization of the microencapsulation, showing that these microcapsules are promising for thermal energy storage and other applications that require high thermal stability.

Language:English
Keywords:phase-change materials, microencapsulation, etherified melamine-formaldehyde resin, thermal stability
Work type:Article
Typology:1.01 - Original Scientific Article
Organization:FKKT - Faculty of Chemistry and Chemical Technology
Publication status:Published
Publication version:Version of Record
Year:2024
Number of pages:18 str.
Numbering:Vol. 16, iss. 17, art. 2463
PID:20.500.12556/RUL-160544 This link opens in a new window
UDC:678.652
ISSN on article:2073-4360
DOI:10.3390/polym16172463 This link opens in a new window
COBISS.SI-ID:205838851 This link opens in a new window
Publication date in RUL:30.08.2024
Views:182
Downloads:26
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Record is a part of a journal

Title:Polymers
Shortened title:Polymers
Publisher:MDPI
ISSN:2073-4360
COBISS.SI-ID:517951257 This link opens in a new window

Licences

License:CC BY 4.0, Creative Commons Attribution 4.0 International
Link:http://creativecommons.org/licenses/by/4.0/
Description:This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

Language:Slovenian
Keywords:fazno spremenljivi materiali, mikroinkapsulacija, eterificirane melaminsko formaldehidne smole, toplotna stabilnost

Projects

Funder:ARIS - Slovenian Research and Innovation Agency
Project number:P2-0191
Name:Kemijsko inženirstvo

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