Morphological, mechanical, and thermal properties of polyurethane nanocomposites co‐incorporated with micro‐Al2O3/nano‐Al2O3 for flexible thermal conductive component applications.

Thermoplastic polyurethane (TPU) nanocomposites (TPU/μmAl2O3‐ACA/nmAl2O3) with excellent mechanical, thermal stability and thermal conductivity were fabricated by co‐incorporating aluminate coupling agent DL‐411 chemically functionalized micron Al2O3 (μmAl2O3‐ACA) and nano‐Al2O3 (nmAl2O3) through melt blending method. FTIR analysis indicated that DL‐411 has been successfully grafted on the surface of μmAl2O3, which was beneficial to the homogeneous dispersion of Al2O3 particles and enhancements of interfacial interactions between Al2O3 particles and TPU matrix. Adding μmAl2O3‐ACA and nmAl2O3 simultaneously showed obvious synergistic effects on improving the mechanical properties of TPU nanocomposites. The optimum mechanical properties were obtained at the mass ratio of μmAl2O3‐ACA to nmAl2O3 of 3:1. Both μmAl2O3‐ACA and nmAl2O3 particles were homogeneously dispersed, constructing relatively perfect thermal conductivity networks, as verified by FESEM and PLM observations. The thermal conductivity (k) of TPU nanocomposites increased continuously with the addition of μmAl2O3‐ACA/nmAl2O3 particles, and the optimal k (0.28 W/m K) was achieved when the mass ratio of μmAl2O3‐ACA to nmAl2O3 was 3:1, which increased by 53% compared with pure TPU (k = 0.183 W/m K). TGA showed that, in contrast to those of pure TPU, the maximum decomposition temperature of TPU/μmAl2O3‐ACA/nmAl2O3 nanocomposites increased by 77.77°C, and the decomposition activation energy of TPU nanocomposite enhanced by 178%. [ABSTRACT FROM AUTHOR]