Branko Alič (Author), Urška Šebenik (Author), Matjaž Krajnc (Author)

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.

Keywords

fazno spremenljivi materiali;mikroinkapsulacija;eterificirane melaminsko formaldehidne smole;toplotna stabilnost;phase-change materials;microencapsulation;etherified melamine-formaldehyde resin;thermal stability;

Data

Language: English
Year of publishing:
Typology: 1.01 - Original Scientific Article
Organization: UL FKKT - Faculty of Chemistry and Chemical Technology
UDC: 678.652
COBISS: 205838851 Link will open in a new window
ISSN: 2073-4360
Views: 19
Downloads: 2
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Other data

Secondary language: Slovenian
Secondary keywords: fazno spremenljivi materiali;mikroinkapsulacija;eterificirane melaminsko formaldehidne smole;toplotna stabilnost;
Type (COBISS): Article
Pages: str. 1-18
Volume: ǂVol. ǂ16
Issue: ǂiss. ǂ17, [article no.] 2463
Chronology: Sep. 2024
DOI: 10.3390/polym16172463
ID: 24866558