Effect of nano-ZnO doping on surface microstructures and properties of cellular porous polyurethane films

This paper aims to obtain a porous polyurethane (TPU) film with regular and orderly distribution of micropores, improve the micro-nano structure of the porous film surface, and improve the wettability of the film surface. The polar molecular characteristics of nano-ZnO are taken advantaged of, TPU is dissolved with tetrahydrofuran (THF) in a solution blending manner, nano-ZnO particles are added for mixing, and micro-droplet template method is used to solidify it into a film to prepare different doping ratios of Nano-ZnO/TPU porous composite film. When the content of nano-ZnO is between 0 wt% to 50 wt%, the microporous structure of the film surface is first ordered and then disordered; when the content of nano-ZnO is 10 wt% (TPU-10), the surface micropores are arranged most densely and orderly, and the static contact angle (CA) of the surface reaches the maximum of 134.5°. Compared with the undoped porous TPU film, the soft segment melting temperature (tm) and hard segment softening temperature (tg) are increased by 51 ℃ and 8.1 ℃, respectively. The decomposition temperature (td) is reduced by 61.1 ℃. When nano-ZnO content is 40 wt% to 50 wt% (TPU-40, TPU-50), after being coarsened by potassium permanganate (KMnO4) and modified by POTS, the CA reaches above 156°. Doped nano-ZnO inhibited the microphase separation of TPU system during the preparation of porous thin films, and made tm and tg of soft segments of porous composite thin films higher than those of TPU-0, while td decreased due to the substitution of hydrogen bonds in some soft segments. When nano-ZnO content is 10 wt%, the micropores on the surface of porous composite film are arranged regularly, and CA reaches the maximum. When nano-ZnO ≥ 40 wt%, the film can be super hydrophobic by KMnO4 roughening and low surface energy modification. © 2021, Chongqing Wujiu Periodicals Press. All rights reserved.