| There has been great interest in reusing of down fiber, which showed excellent physical and chemical properties compared with synthetic polymers. In this paper, the down fiber was grinded into superfine down powder by purposely designed mill, and the average diameter of superfine down powder is 2.53μm. In order to improve the water vapor transport property of PU film, the PU/superfine down powder blend films were prepared and the internal structure of them was investigated.This paper discussed processing factors, such as temperature, thickness of molding and DMF content of coagulation bath, which influence greatly the properties of PU film. As the increasing temperature of processing, the density of PU film was increased and the porous structure of PU film was transferred into dense structure, which decreased the water vapor transport property of PU film. When the thickness of PU film was 0.07mm, the water vapor flux of PU film was 7132.4g/m2·day, which was decreased around 71.9% when thickness of PU film reached 0.10mm. However, the water vapor flux of PU film was not decreased remarkable when the thickness over 0.10mm. The diffusion speed of DMF in PU solution decreased when DMF was added into coagulation bath, which also resulted into the forming of dense structure of PU film.Compared with other protein materials, the superfine down powder showed excellent swelling property. The volume of superfine down powder was increased by 50% when powder was put into DMF solution. The property of swelling was increased with the increasing average diameter of down powder.Based on the SEM photos of PU/superfine down powder blend films, as the increasing content of superfine down powder, the surface of blend film was plain and the cross section showed larger hole, and the quantity of hole was increasing. FTIR-ATR spectra showed that there was no chemical bonding between PU molecular and superfine down powder until the powder content was 30% while the down powder formed hydrogen bond with PU molecular. WXRD diffraction curves showed the crystalline structure of PU was reduced by addition of superfine down powder. TGA data of PU/superfine down powder blend film indicated the improving initial thermal decomposition, increasing property of moisture and content of residue. According to the DTG, the typical thermal decomposition peak of hard segment disappeared due to the destruction of superfine down powder. The water vapor flux of blend film was increased with the increasing content of down powder. Moreover, the mechanical properties was decreased at same time.Compared with superfine down powder, the coarse down powder can further decreased the density of PU/coarse down powder blend film, which showed lower water vapor flux than that of PU/superfine down powder blend film. Coarse down powder also decreased the mechanical properties of blend film.Superfine down powder, superfine wool powder and fine wood powder were blended with PU respectively, and the properties of blend film were compared with each other. All of the three kinds of organic powder can decrease the density of blend film, but increase the size of hole and quantity of hole in blend film. Compared the three kinds of blend film, the influence of superfine wool powder on structure of PU film was smaller, but the influence of fine wood powder was larger. FTIR-ATR spectra of blend film showed that there was no chemical bonding between PU molecular and all of three kinds of powder, which destroyed the crystalline structure of PU film from the X-ray diffraction curves. Based on TGA data, the hard segment of PU film was destroyed by all three kinds of powder, but the moisture, initial thermal decomposition and residue were increased. The DTG analyzed data showed the destruction of superfine wool powder on hard segment was smaller and the destruction of fine wood powder was larger. PU/superfine down powder blend film, PU/superfine wool powder blend film and PU/fine wood powder blend film showed improving water vapor flux property compared with water vapor flux of pure PU film,. The water vapor flux of PU/superfine down powder blend was improved largely, and that of PU/fine wood powder blend film was improved smaller. The mechanical properties of blend films were decreased whichever powder was added into PU film.
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