October 2019 Abstracts

The Effect of Incorporating Hydroxyapatite and Silica Nanoparticles in Polyethylene Surface Treatment of Natural Leather

by E. Jowshan and A. Ershad-Langroudi

Leather is a natural material which is used widely in different industries. It is prone to lose moisture due to environmental conditions. Consequently, leather becomes hard and fragile, which leads to poor durability. A novel mixed system of Poly (ethylene glycol), Hydroxyapatite, plus Silica nanoparticles enhanced the mechanical, thermal, optical, and aging properties of the natural leather properties. This system also enabled the retention of moisture in leather. Thanks to the reinforcing properties of hydroxyapatite/silica nanoparticles, and the lubricating effect of poly (ethylene glycol), these modifying agents enhanced the mechanical and thermal properties of leather and preserved the leather’s natural color and gloss.

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Effect of an Amphoteric Chromium-free Polymer Retanning Agent with Reactive Aldehyde Groups on Collagen Fibers

by Xuechuan Wang, Dongyan Hao, Xiaoye Chai and Ji Li

A chromium-free amphoteric polymer retanning agent was prepared by free radical polymerization reaction of undecylenic aldehyde (UAL), acrylic acid (AA) and dimethyl diallyl ammonium chloride (DADMAC) as raw materials. The structure of amphoteric polymer retanning agent was characterized by FT-IR and 1H-NMR. Amphoteric polymer retanning agent was applied to the retanning of vegetable-tanned light leather to investigate the binding ability of crust leather to anionic dyes, fat liquoring agent and physical-mechanical properties of the crust leather. The results showed that the synthesized amphoteric polymer retanning agent was successfully prepared. The application trial indicated that the amphoteric polymer retanning agent can improve the binding capacity between leather and anion dye and fat liquoring agent in the retanning process. The dye absorption rate of the crust leather was up to 99.58% and the dyeing liquor was clear. Furthermore, color of the crust leather was uniform and full and its K/S value and drywet rub fastness, thickening rate and physical-mechanical properties were higher than that of the retanned leather by acrylic resin retanning agent. In addition, the crust leather after retanning with amphoteric polymer retanning agent has good softness, and the absorption rate of fat liquoring agent was 99.62%. The above results showed that amphoteric polymer retanning agent possessed the good retanning property in vegetable tanned sheep garment leather.

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Determination of Free Formaldehyde in Leather Chemicals

by Yudan Yi, Wei Ding, Ya-nan Wang and Bi Shi

Formaldehyde is widely used in the synthesis of various leather chemicals due to its high reactivity and low cost. It is probably introduced into leather when applying the chemicals to processing, and then released during storage and use of leather, which may pose a potential risk to human health. Existing method for determining formaldehyde in leather is helpless to deal with the complicated chemicals. In this study, a method was optimized for determination of free formaldehyde in leather chemicals based on ISO 27587. A 0.5-2.0 g sample of leather chemical (formaldehyde could range from 1.25 to 1250 mg/kg) was heated at 90°C in nitrogen atmosphere. The released formaldehyde was purged at a flow rate of 300 mL/min for 30 min, captured and derivatized using a bubble absorption tube containing 2,4-dinitrophenylhydrazine absorption solution, and then detected by HPLC-diode array detector. The recovery rate of formaldehyde standard solution was 91.0% with relative standard deviation (RSD) of 4.87% in seven times repeated trials. The repeated determinations of aldehyde tanning agents showed the formaldehyde recoveries higher than 90% and RSD lower than 7%, indicating the accuracy and precision of the method. Powdery amino resins were determined to contain a tiny amount of free formaldehyde using this method. However, it should be noted that hydrolyzed formaldehyde will be formed when the amino resins were dissolved in water and used in retanning, leading to the potential for bringing leather with high content of formaldehyde.

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Effect of Ionic Liquids Pretreatment on the Extraction of Collagen from Calf Skin

by Sicong Liu, Wentao Liu and Guoying Li

The use of ionic liquids (ILs) for collagen extraction should be premised of not destroying the triple helix structure of collagen. Herein, the effects of pretreatments by two imidazolium based ILs with different anions, 1-ethyl-methylimidazolium dicyanamide ([EMIM][N(CN)2]) and 1-ethyl-methylimidazolium tetrafluoroborate ([EMIM][BF4]), on the extraction of collagen from calf skins were studied. The dependences of ILs pretreatments on ILs species and concentrations (30%, 50%, and 70% (w/w)) were examined, in terms of the fiber morphology of skins as well as the extraction rate, structural integrity, thermal stability, and aggregation behaviors of collagens. The results of histological analysis and scanning electron microscopy showed that the skin fibers were effectively loosened by the IL s pretreatments. The extraction rate of collagen was improved as the increase of ILs concentration and polarity with the highest value of 28.79%. Moreover, sodium dodecyl sulphatepolyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy confirmed that the structural integrity of collagen was maintained after ILs pretreatments, although the thermal stability of collagen was determined to be slightly decreased by ultra-sensitive differential scanning calorimeter. Finally, pyrene fluorescence analysis and atomic force microscope indicated that the aggregation behavior of collagen was weakened when increasing the ILs concentration and polarity. The green ILs pretreatment of calf skins might be used as an effective approach for the extraction of bioactive collagen with improved yield and purity.

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