Multiple Hydrogen-Bonding Polyurethane Emulsions for Application on Human Skin

In order to meet the requirement for direct contact with the skin surface while ensuring comfort through suitable mechanical properties such as elasticity, breathability, and moisture permeability, multiple hydrogen-bonding polyurethane (PU) emulsions were developed using hydrophobic polytetramethylene ether glycol as the soft segment, isophorone diisocyanate as the hard segment, and particularly incorporating various quantities of decanoylhydrazide (SD) into the main chain and ureidoxaporphyrinone (UPy) into the side chain. UPy is a benefit not only for the formation of hydrogen bonding interaction within the PU but also for the emulsification of PU. The as-obtained PU emulsions can quickly form dry films with moderate adhesive strength (756.5–991.5 kPa) on the skin even under water, and yet, the films are peelable or removable with 70% ethanol. The PU films with adequate contents of SD and UPy units have excellent comprehensive mechanical properties, that is, an elastic modulus of 4–6 MPa, a tensile strength of 4.3–15.3 MPa, and a stretchability of 999–1120%. The PU films also have extremely high air/water permeability, i.e., a water vapor transmission rate of 835.2–1664.4 g/(m 2 ·24 h) and a gas transmission rate of 523.3–600 cc/(cm 2 ·d·0.1 MPa). Both the mechanical properties and the permeability fully satisfy their comfortable application on human skin. The applicability of the PU emulsion on human skin was primarily confirmed by applying it on hand.