Down feathers, which are used as a filling material for duvets and winter clothes because of their excellent heat retention, are obtained mainly from domestic geese and ducks, but some are obtained from wild eider ducks. It is important to determine from which bird down was taken because the quality and price of down vary greatly depending on the bird species. In this study, infrared spectroscopy instead of the conventional microscopic observation was used to identify the bird species from which down was obtained. Goose down and duck down could be accurately identified by selecting an appropriate wavenumber region of the infrared (IR) absorption spectrum obtained using the attenuated total reflection (ATR) method and the partial least squares discriminant analysis (PLS-DA) method. Score plots based on principal component analysis (PCA) were found to be effective for identifying eider duck down and non-eider duck down.

We previously reported that a scaled-down chitin nanofiber (SD-ChNF) dispersion can be obtained from partially deacetylated chitin nanofiber films by ultrasonic treatment in 1.0 mol/L aqueous acetic acid. In this study, we demonstrated that hydrogelation from SD-ChNFs occurs via the reductive amination of monosaccharide residues with the amino groups of chitin. The reductive amination of D-xylose (Xyl) was carried out in the presence of NaBH3CN as a reducing agent in the SD-ChNF/aqueous acetic acid dispersion to produce the Xyl-modified ChNFs. Under selected conditions, a hydrogel was formed in the reaction mixture. The scanning electron microscopy (SEM) image of the lyophilized hydrogel product displayed a network structure at the nanoscale. Hydrogels were also prepared by the reductive amination of D-glucose and N-acetyl-D-glucosamine on SD-ChNFs under the same conditions. Furthermore, the lyophilized products were re-swollen in water, and their weak gel behaviors were characterized by dynamic viscoelastic measurements. Based on the results of reductive amination, precisely performed under various conditions, a mechanism for hydrogelation via the formation of a network structure during reductive amination is proposed.

This work addresses the challenge of improving the sound absorption at medium and low frequencies by developing an advanced and low-cost porous composite utilizing the unique properties of PS fibrous membranes. A novel multi-layer hybrid, consisting of sound absorption nonwovens (SAN, 10 mm needle-punched PET nonwovens) and electrospun polystyrene (PS) porous membranes, is developed. The formation and the effect of the porous structure on the sound absorption property are studied. The results show that the surface structure is affected by the solvent, relative humidity and temperature. Furthermore, electrospun PS fibrous membranes have smaller pores and narrower pore size distribution but higher porosity, which have better sound absorption properties. The average sound absorption coefficient of commercial sound absorption PET nonwovens with thickness of 1cm is 0.188, however, the coefficients of the hybrids are 0.335, 0.343, 0.395 and 0.430 when the sound absorption PET is combined with electrospun PS layer with thickness of 0.4mm, 0.8mm, 1.2mm and 2.0mm respectively. The average sound absorption coefficient of hybrids with electrospun PS layer with porous surface is 0.468, indicating that the sound absorption of SAN can be significantly improved by composing with electrospun PS layers. Moreover, the porous surface can further improve the sound absorption properties. Therefore, the combination of electrospun membranes with porous structure and needle-punch nonwovens would be an efficient way to improve the sound absorption performance. The composite materials have the advantage of the low cost, light weight and good sound absorption effect, which have a broad prospect in sound absorption fields.