Layered double hydroxide/polyurethane composites: Influence of micron-sized LDH on the gas barrier properties of polyurethane

Abstract

Enhancing the gas barrier performance of polyurethane (PU) via functional additives has garnered growing interest to expand its application scope. Herein, we synthesized a series of micron-sized Mg₂Al-layered double hydroxides (LDHs) via hydrothermal method by varying Mg²⁺ concentrations (denoted as 0.1-, 0.4-, 0.6-, 0.8-, and 1.0-LDH). Subsequently, LDH/PU composite films were fabricated by dispersing Mg₂Al-LDH into the PU matrix using a solvent mixing approach. Comprehensive characterization of crystalline structure, morphology, gas barrier performance, thermal stability, and mechanical properties was conducted. Results revealed high dispersion of LDH fillers within the PU matrix without adverse effects on PU crystallization. Among them, notably, 0.2-LDH/PU composites exhibited significantly enhanced gas barrier properties compared to neat PU, with a 5 wt% loading of 0.2-LDH identified as optimal for superior barrier performance. The improved gas barrier performance stems from hydrogen bonding interactions between LDH hydroxyl groups and PU amino groups, which enhance filler-polymer compatibility and suppress PU hard segment mobility. Additionally, LDH incorporation effectively reinforced the thermal stability and mechanical properties of the composites. These findings highlight micron-sized LDHs as promising functional additives, paving the way for future development of high-performance PU with tailored gas barrier capabilities.