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

Abstract Thermoplastic polyurethane (TPU) nanocomposites (TPU/μmAl 2 O 3 ‐ACA/nmAl 2 O 3 ) with excellent mechanical, thermal stability and thermal conductivity were fabricated by co‐incorporating aluminate coupling agent DL‐411 chemically functionalized micron Al 2 O 3 (μmAl 2 O 3 ‐ACA) and nano‐Al 2 O 3 (nmAl 2 O 3 ) through melt blending method. FTIR analysis indicated that DL‐411 has been successfully grafted on the surface of μmAl 2 O 3 , which was beneficial to the homogeneous dispersion of Al 2 O 3 particles and enhancements of interfacial interactions between Al 2 O 3 particles and TPU matrix. Adding μmAl 2 O 3 ‐ACA and nmAl 2 O 3 simultaneously showed obvious synergistic effects on improving the mechanical properties of TPU nanocomposites. The optimum mechanical properties were obtained at the mass ratio of μmAl 2 O 3 ‐ACA to nmAl 2 O 3 of 3:1. Both μmAl 2 O 3 ‐ACA and nmAl 2 O 3 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 μmAl 2 O 3 ‐ACA/nmAl 2 O 3 particles, and the optimal k (0.28 W/m K) was achieved when the mass ratio of μmAl 2 O 3 ‐ACA to nmAl 2 O 3 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/μmAl 2 O 3 ‐ACA/nmAl 2 O 3 nanocomposites increased by 77.77°C, and the decomposition activation energy of TPU nanocomposite enhanced by 178%.