Thermal and morphological studies on novel PCM microcapsules containing n-hexadecane as the core in a flexible shell

- Development of a new generation of PCM microcapsules resistant to break for thermal energy storage applications.
- Correlation between thermal and morphological properties of flexible and rigid PCM microcapsules and their comparison.
- Influence of comonomer ratio on encapsulation efficiency and thermal properties.
- Observing different morphologies with the changes in polarity of the shell.

Herein, a series of microcapsules, containing n-hexadecane (HD) as the core, and polymethyl methacrylate (PMMA) and poly(butyl acrylate-co-methyl methacrylate) (poly(BA-co-MMA)) as the shells were prepared through suspension polymerization. The aim of this work was to investigate the effect of shell flexibility on the encapsulation efficiency and thermal performance of the microcapsules. Kinetics and thermodynamic studies based on propagation rate constants for the monomers and the polarity of the system were employed to predict final morphology of the microcapsules. To this aim, contact angle and interfacial tension analysis were performed, and the results of morphology prediction were affirmed by SEM. A multi-nucleus morphology was observed for microcapsules with PMMA shell and a matrix-type morphology was detected for poly(BA-co-MMA) with high BA content. Thermal properties of the microcapsules were evaluated by DSC and DMTA was performed to assess the rigidity of shells with two distinct Tgs for poly(BA-co-MMA). Appropriate thermal storage behavior plus flexibility of the shell in PCM microcapsules must be considered simultaneously for efficient applications. Here, poly(BA-co-MMA) (with BA content below 25 wt%) as the shell was nominated for this reason.

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