Research On The Separation Of Keratin Whisker Of Wool Fiber And Its Application

Wool is a kind of important natural keratin fiber in textile industry.Each year,a great deal of short and coarse wool are produced in wool shearing and processing. These wasted wool fibers are usually discarded as waste because of its bad spinnability.However,the wool fiber is almost composed of keratin,which is a sort of resources of keratin.It is meritorious to recycle these materials,even though there are many difficulties in the reutilization of wasted wool.Keratin solution extracted from wasted wool fiber is difficult to be spun into filaments due to its special molecular conformation.Thus,the keratin solution is used to make films and some filler material.If wool fiber was partially separated into its hierarchical components and the keratin whisker was extracted,the keratin whisker might be blended with keratin solution to construct the novel keratin composite fiber.Besides,the dimension of keratin whiskers is in sub-micron/nano scale.They are small fibers in anisotropic shape.The molecular conformation of keratin whisker was maintained in consistent with the wool fiber;therefore,the keratin whisker possesses good mechanical properties as well as the excellent performance of wool fiber.It can be served as a good natural material for synthetic fiber modification and filler material of natural polymer composite.As a result,extraction of keratin whisker by partially separation of wool fiber provides a novel train of thought for recycling of wasted wool fiber.The fractal structure of wool fiber has been studied.The result indicated that "7+2" model was more reasonable than "9+2" one.The fractal dimension of para-cortex was a little bit smaller than that of the ortho-cortex.Thus,the density of microfibrils in the para-cortex was less than that of the ortho-cortex,and the energy for separation of the microfibrils in the para-cortex was relatively low,so that to separate the para-microfibrils was easier.In addition,the difference between fractal dimension of the second hierarchic component and the third hierarchic component is larger for para-cortex than for ortho-cortex,which suggested that the microfibrils in para-cortex was easier to be separated,as well.The swelling of wool fiber was characterized by extension of the fiber diameter,i.e. diameter swelling ratio.The diameter swelling ratio of wool fiber in 98%formic acid and 10%peracetic acid was 81.7%and 84.4%,respectively.The swelled wool fiber could be easily separated into cortical cells and macrofibrils under shearing force.The high swelling ratio of wool fiber provided a beneficial pre-treatment condition for separation of wool fiber components with even smaller scale.However,eventhough the diameter swelling ration of wool fiber researched 170%in the solution of sodium disulfite-urea,this reagent was not appropriate to be served as the swelling reagent for separation of wool fiber components.Since this reductive agent caused severe damage to the microfibril.Ultrasonic disintegration is an efficient method for extraction of cortical cells and macrofibrils.The parameters related to the ultrasonic decomposition of wool fibers in formic acid were investigated in this paper.The results indicated that the disintegration ratio of wool fibre increased under the condition with high output power of a transducer,high temperature,ultrasonic conditions with a short operation period,low probe position,round shaped vessel,and a solid/liquide ration of 1g/50ml. Moreover,the disintegration ratio of descaled wool fibre was about four times as much faster as the undescaled one.The productions obtained in different density and different dimension were separated from each other by the combination of screening, differential centrifugation and density gradient centrifugation.The mechanism investigation in the separation of swelled wool fiber revealed that modulus of matrix between the microfibrils sharply decreased during this swelling process,which was the basic reason for rapid decomposition of wool fiber.Moreover, the kinetic analysis indicated that the disintegration ratio of wool fiber was in exponential relationship with ultrasonic treatment time.Both output power of a transducer and temperature had an effect on the disintegration rate of wool fiber, especially for the parameter of transducer output power.Separation and extraction of cuticle cell,cortical cell,macrofibril and microfibril were investigated,respectively.The wool fiber was successfully descaled by a pretreatment of boiling in formic acid following with a short time ultrasonication in formic acid,and about 98%cuticle cells was removed.Cortical cell(3-4.5μm in diameter and 80-100μm in length) was obtained by ultrasonication of descaled wool fiber in formic acid.The production of cortical cell could be accelerated when the descaled wool fiber undergoes a mild oxidation pretreatment in 1.6%peracetic acid before ultrasonication treatment with and yield of 30.4%.When the separated orthocortical cell oxidized in 1.6%peracetic acid for 5mins was ultrasonicated in formic acid for 2hours,the macrofibril(0.32-0.48μm in diameter and 10-25μm in length) was separated with a productive rate of 25.1%.Both orthocortical cell and paracortical cell was potential to be disintegrated into the nano scale component,the microfibril.We observed the separation of microfibril assembly(about 100nm in diameter) from macrofibril of paracortical cell.The microfibril was about 100nm in diameter.The macrofibrils with a steady productive rate could be successively obtained with the method provided in this present paper.Eventhough the yield of microfibril assembly(about 100nm in diameter) was very low;the method for separation of microfibrils was feasible.FT-Infrared spectrum and X-ray diffraction were employed to investigate the molecular structural changes and the aggregation structural variation of wool fiber by the chemical treatment for extraction of cortical cell.The result showed that short time oxidation treatment in dilute peracetic acid can selectively break the disulphide bond in the matrix region.Consequently,the chemical bonding force was declined to facilitate breakdown of wool fiber.In addition,Raman spectrum was introduced to study the molecular structural changes and the aggregation structural variation of chemical treated cortical cell.The result revealed that enzyme hydrolysis and oxidation treatment caused conformational changes of cortical cell fromα-helix toβ-plated sheet.Meanwhile,the conformation of disulphide bond transformed from g-g conformation to g-t conformation.Therefore,the combination of oxidation treatment and enzyme hydrolysis treatment was relatively efficient for selective cleavage of disulphide bond and separation of microfibril.For application of the separated wool fiber components,a cortical cell reinforced chitosan biocomposite film was prepared and tested.The cortical cells were evenly dispersed in the composite film.There was no chemical reaction between cortical cells and chitosan.The bonding between cortical cells and chitosan was physical action.The crystallinity of the composite films increased with increasing content of cortical cells,and the mechanical and thermal properties of the composite film was improved as well。...