The Influence of TPU Shell Chemistry and Composition on the Performance of N-Tetradecane-Loaded Phase Change Microcapsules

Abstract

Phase change Materials (PCMs) are crucial in thermal energy storage due to their capacity to absorb and release heat during phase transitions. This study systematically investigated the influence of thermoplastic polyurethane (TPU) shell chemistry and composition on the performance of n-tetradecane-loaded phase change microcapsules, prepared via the phase separation method, for potential use in low-temperature applications. Two distinct shell matrices were engineered: a rigid, aromatic structure based on MDI (TPU-A) and a flexible, aliphatic structure based on IPDI (TPU-B), both incorporating dynamic disulfide (-S-S-) bonds from a DPA chain extender. The results demonstrate that the flexible aliphatic architecture of TPU-B, combined with a 1:1 PCM-to-shell ratio, yielded microcapsules with superior latent heat capacity and minimal leakage, as its compliant matrix effectively accommodated PCM volume changes. Conversely, the rigid aromatic structure of TPU-A severely restricted PCM crystallization, leading to significantly reduced thermal performance. The findings establish that the chemical nature of the diisocyanate is a dominant factor in microcapsule performance, providing a critical guideline for the rational design of high-efficiency polymeric shells for thermal energy storage.