Study On The Preparation And Properties Of Wool Keratin Membrane Material Modified By Polyurethane

The environmental pollution caused by solid waste has been worsening inrecent years. Therefore, the technology of recycling, harmless and reducingtreatment of solid waste has become a hotspot of research in the era ofsustainable development.Wool keratin is a kind of natural protein resource generated as solid wastefrom the unhairing procedure in leather manufacture. It has goodbiocompatibility, non-toxic and skin-friendly features. If used effectively, it cannot only reduce BOD load, COD load, suspended solids, and environmentpollution, but also enable the waste wool resource to achieve its remained value.It is known that hair keratin has certain limitations, due to its molecular weightand hydrophilic group of the peptide chain, if used alone directly as coatingagent. The keratin was modified with waterborne polyurethane in order toimprove the performance of keratin.Firstly, the wasted wool was dissolved in method of reduction. Keratin wasseparated in method of isoelectric precipitation, then determined andcharacterized it after purification. It was suggested that characteristic absorptionpeaks of keratin amide group appear in IR figure showed that recovered keratinretained the original backbone structure. The molecular weight of keratin was1451, which was moderate. It indicated the recovering value of keratin have acertain processing value.Secondly, the influence factors of waterborne polyurethane synthesis ofepoxy-terminated was analyzed. Testing and characterizing of the polyurethaneduring the process was conducted. The results was shown as followed.(1) The comparison between the synthesis of the polyurethane prepolymerin different feeding methods showed that the waterborne polyurethane emulsion and film obtained by two-step was better than those obtained by one-step. Theconcentration of-NCO was determined by dibutylamine tracking method atdifferent times. It showed that the concentration of-NCO gradually becomestable after four hours. Therefore, it is assumed that4h is the appropriate time forpre-polymerization synthesis. By comparing the viscosity and emulsificationcondition of prepolymer at different reaction temperatures, the temperature ofpre-polymer was determined as50~60℃.The effects of DMPA amount onemulsion and film performance was also examined in the experiment. When theconcentration of DMPA was3~5%, the emulsion appeared good stability and thefilm generated good water resistance.(2) The reaction condition of glycidyl-terminated polyurethane was studied,and the result showed that the reaction temperature was40℃and the reactiontime was2.5h;(3) The FTIR spectra showed that the stretching vibration peak of epoxygroup appeared near928.73cm-1. The absence of stretching vibration peak of-NCO around2300cm-1suggested that there is no presence of-NCO stretchingvibration peak in the product. Videlicet, epoxy groups had been successfullyintroduced into the side chain of the polyurethane to achieve the blockage ofWPU molecular chain.Lastly, the preparation condition of keratin modified by polyurethaneprepolymer was studied, and the modified keratin was testd and characterized.The results were shown below.(1) The optimum reaction condition of keratin modified by polyurethaneprepolymer was that the reaction temperature was45℃, the reaction time was1hand the reaction pH was8.(2) When the amount of keratin was remained at50%, the film showedexcellent hydrophobicity, wettability, water resistance and small absorption oftoluene. However, the vapor permeability and the gas permeability of the filmwas reduced.(3) Infrared spectroscopy of keratin modified by polyurethane prepolymershowed that there was no vibration absorption peak of N-H around1654.8cm-1,and no characteristic absorption peaks of epoxy groups around928.73cm-1. Itcan be determined that the amino groups in keratin were totally reacted. It showed that-NH2participated in the reaction with epoxy groups to make thepolyurethane and keratin copolymerized successfully. The molecular weight ofthe modified copolymer was42194, showing that the molecular weight of graftcopolymer was lager than that of the keratin, and the copolymerization wasoccurred.(4) The figure of TG-DSC showed the thermal stability and water resistanceof polyurethane prepolymer modified keratin was improved.