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Preparation and surface properties of cashmere guard hair powders
Kiran Patil a, Rangam Rajkhowa a, Xiujuan J. Dai a, Takuya Tsuzuki a, Tong Lin a, Xungai Wang a,b,⁎a Centre for Material and Fibre Innovation, Deakin University, Geelong, VIC 3217, Australiab School of Textile Science and Engineering, Wuhan Textile University, Wuhan, China
⁎ Corresponding author at: Centre forMaterial and FibrGeelong, VIC 3217, Australia. Tel.: +61 3 522 72894; fax:
Cashmere guard hair, a by-product from the cashmere dehairing industry is used for low value applicationsbecause the guard hairs are not suitable for spinning as they are coarse, contain large medullation and lackcrimp or curvature. To find new uses in high value-added applications, cashmere guard hairs were milledinto fine particles using the processing sequence Chopping→Attritor milling→Spray Drying→Air Jet mill-ing. The guard hairs were partially hydrolysed with hydrochloric acid which increased the pulverisationrate due to the deterioration in mechanical properties. The volume median particle size d(0.5) was reducedfrom 2.328 μm, for untreated cashmere guard hair powder to 0.461 μm for powder from the acid hydrolysedguard hairs. FTIR and XPS studies revealed the breakdown of the cashmere guard hair cuticle cells and theexposure of the cortex on the powder surface along with the oxidation of the cashmere guard hair duringmilling.
Cashmere goats (Capra hircus laniger) produce one of the finestanimal fibres. The soft and light fibres from the downy undercoatare always covered with an outer coat of coarse hairs. These coarsehairs, known as guard hairs, are present throughout the year and pro-tect the fine fibres which grow underneath during autumn and earlyto mid-winter [1]. As a result, sheared cashmere goat fleece contains amixture of guard hairs and fine cashmere fibres. The process to sepa-rate guard hairs from fine fibres is known as “dehairing”. The separat-ed fine cashmere fibres are used for making premium fabrics fetchinga very attractive price, while the guard hair either goes as a waste orgets used in low value applications such as brushes and interlinings.
The total annualworld production of cashmerefleece is about 8000–10,000 tonnes [2], of which only 17 to 50% are fine cashmere fibres [1].Since guard hair is themajor proportion of cashmere fleece, the conver-sion of these waste fibres into a new value-addedmaterial for technicalapplications could greatly assist the sustainability of the cashmereindustry.
Recently, there has been growing interest in developing new usesof animal protein fibres such as silk and wool by converting them intofine powders [3–5]. Due to their biocompatibility, biodegradability,and moisture retention properties, many new applications havebeen identified for these protein fibre powders. For example, silkpowder has been commercially utilised as an ingredient in cosmetic
e Innovation, DeakinUniversity,+61 3 522 72539.
rights reserved.
formulations [6]. Wool powder has been used to coat cotton fabricto manipulate water and thermal transport properties [3]. Wool andsilk powders have shown better performance than commercial ionexchange resins in binding of transition and heavy metal ions [4,5].The silk particles have been demonstrated to have potential applica-tions in drug delivery [7]. It is likely that, cashmere guard hair powdercan also be used in similar or many new applications.
Powder from fibrous materials can be made either by a solutionroute or a mechanical route. In the solution route, protein solutionprepared from fibres is converted into powder by freezing and lyoph-ilizing [8,9]. However, the solution route is lengthy, costly and oftenrequires harmful chemicals. On the other hand, the mechanical pow-der fabrication route is a quicker and safer option. However, it canalso be challenging due to the viscoelastic nature of fibrous materials.Modifications of the fibres with sodium carbonate [10], sodium hypo-chlorite [11,12], hydrogen peroxide [13], tri-n-butylphosphine, thio-glycollic acid [14], peracetic acid and sodium sulphite/sodiumhydroxide mixtures [15] and explosive puffing with saturated steam[14] have been examined to facilitate the milling process. In spite ofimprovements in milling, the degradation of protein in a high energymilling environment still remains a problem. Previously we reportedon the fabrication of silk powder by a milling sequence that couldavoid the protein degradation problem [16]. In this study we haveused a similar milling process to fabricate ultrafine cashmere guardhair powder, and have examined the influence of acid hydrolysis ofcashmere guard hair on its milling behaviour.
The mechanical properties of the fibres are important determi-nants for the powder production process and the properties of theresulting powders. Although numerous studies have been conductedin the past to characterise physical and mechanical properties of fine
Control Cashmere guard hair (no treatment) CHF4 h partially hydrolysed Cashmere guard hair PH4CHF10 h partially hydrolysed Cashmere guard hair PH10CHFSpray dried particles made from CHF CHF-AMSpray dried particles made from PH4CHF PH4CHF-AMSpray dried particles made from PH10CHF PH10CHF-AMAir jet milled particles made from CHF-AM CHF-AJAir jet milled particles made from PH4CHF-AM PH4CHF-AJAir jet milled particles made from PH10CHF-AM PH10CHF-AJ
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cashmere fibres [17–21], cashmere guard hairs have received little at-tention due to their low commercial value. Therefore, we have alsodetermined the tensile strength and bending abrasion resistance ofcashmere guard hairs along with the effect of partial acid hydrolysison these properties.
2. Materials and methods
2.1. Material preparation
Cashmere guard hairs were supplied by Cashmere Connections PtyLtd, Australia. Before any further processing, the vegetable mattersand other contaminants were separated by a sample carding machine(Mesdan, Italy). The guard hairs were passed three times through thecard to achieve maximum cleaning. Any remaining adhered contami-nants were further separatedmanually. Part of the cleaned hair was di-rectly milled and the other part was acid treated before milling. Partialacid hydrolysis of the clean guard hairs was carried out, following theprocess developed by Előd et al. [22], in a Thies Eco-Block LFA packagedyeingmachine by using a loose stock carrier. Guard hairs were treatedwith 1 M HCl (35% AR grade fromMerck) and 1% (wt/wt) Hydropol TN450 (a non-ionic detergent fromM/s Huntsman) at 80 °C with a materialto liquor ratio of 1:68. Batch size of guard hairs was 500 g and treatmenttimewas 4 h or 10 h. The hydrolysed guard hairs were rinsed with waterat room temperature followed by neutralising with 0.1% ammonia solu-tion (30%, AR grade from Chem Supply). Any remaining free ammoniawas removed by two final cold water rinses. The hydrolysed guard hairswere dried overnight in a laboratory convection oven (Heraeus Oven,Thermo Scientific) at 60 °C. The weight loss on hydrolysis was determinedby weighing the guard hairs before and after hydrolysis, after condition-ing at 65±2% RH and 20±2 °C for 48 h.
2.2. Measurement of guard hair diameter and mechanical properties
The diameter of the cashmere guard hair diameter was measuredon a Single Fibre Analyser (SIFAN from BSC Electronics, Australia)using a sample of randomly selected 50 single guard hairs.
Single guard hair tenacity was measured using the SIFAN to deter-mine the level of damage caused by acid hydrolysis. A gauge length of40 mm and jaw separation speed of 500 mm/min were used duringthe breaking load measurements. 50 guard hairs were tested foreach control and hydrolysed batch. The linear density in dtex orgramme per 10,000 m was calculated by weighing 100 guard hairscut to 40 mm from the middle hair portion. Guard hair tenacity wascalculated from breaking load and linear density.
The cyclic bending abrasion resistance of single guard hairs wasmeasured on a FibreStress Tester (Textechno, Germany). The hairswere traversed over a 2 mm diameter stainless steel wire for 10 mmdistance at 90º arc under 0.8 g tension. The number of cycles requiredto break the hair was automatically recorded by the instrument. Atotal of 70 hairs were tested for each sample. The mean and standarddeviation of the number of cycles required to break the guard hairwere calculated. The guard hairs were conditioned at 65±2% relativehumidity and 20±2 °C for at least 48 h before the tests.
2.3. Powder production
The cashmere guard hair was converted into dry powders by fol-lowing the powder fabrication sequence previously developed inour research group [16]. Briefly, the control and partially hydrolysedcashmere guard hairs were initially converted into 1–2 mm snippetsby processing them through a rotary blade cutter. 200 g of eachfibre snippet sample were wet milled in an attritor (IS, Union Process,USA) using 20 kg yttrium doped zirconium oxide grinding media(5 mm) in a Teflon coated 9.5 l tank. Deionised water was used toachieve a 1:10 material (kg) to liquor (L) ratio during milling. Stirrer
speed and milling time were 280 rpm and 6 h, respectively. The wetmilled slurry was then processed through a laboratory spray drier(B-290 from Buchi Labortechnik AG) to form dry powder samples.The spray dried particles were further milled in a Sturtevant laborato-ry air jet mill with 110 psi grinding air pressure.
The cashmere guard hairs and powders are henceforth denoted bytheir nomenclatures as specified in Table 1.
2.4. Particle size measurement
AMalvern Instruments Mastersizer 2000, which uses laser diffractionto measure particle sizes, was used in this study. The dispersion medi-um used during measurement was deionised water for attritor millslurry and propan-2-ol (from Sigma-Aldrich) for spray dried and air jetmilled powders. A refractive index of 1.553 and imaginary refractiveindex of 0.01 for the cashmere guard hair and its powders were usedfor the measurements. The volume-based size distribution of particleshas been used for reporting all particle size measurements. The d(0.1),d(0.5) and d(0.9) values indicate that 10%, 50% and 90% of the particlesmeasured were less than or equal to the size stated. The span (η) is thewidth of the particle size distribution based on d(0.1), d(0.5) and d(0.9)which is calculated according to Eq. (1) [23]:
η ¼ d 0:9ð Þ−d 0:1ð Þd 0:5ð Þ : ð1Þ
There was no significant variation between the three d(0.5) mea-surements per powder sample from the Mastersizer 2000 and henceno error bars are plotted while reporting the results.
2.5. Scanning electron microscopy (SEM)
The morphologies of the milled powder and untreated cashmereguard hair were observed by SEM(Zeiss Supra 55VP) at 5–10 kV acceler-ated voltage and 8–9 mm working distance. The cross section of thecashmere guard hair was observed by embedding the guard hairs in aresin (TAAB, England) using a mould, followed by curing the resin at60 °C overnight and subsequently cutting it into 5 μm slices using a mi-crotome (CUT 5062 SLEE MAINZ, Germany). The samples were sputtergold coated (Bal-Tec sputter Coater SCD 050) before imaging.
2.6. Measurement of BET surface area
The BET surface areas were determined by the N2 gas adsorptiontechnique using a Tristar 3000 instrument. Approximately 0.5 g ofspecimenwas placed in a glass sample holder. In the case of cashmereguard hair, 2–3 mm snippets were used for the measurements. Thesamples were degassed under N2 gas at 110 °C for 60 min prior togas adsorption measurement under cryogenic conditions. Three mea-surements were made for each sample.
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2.7. FTIR ATR
The Fourier transform infrared (FTIR) spectra of cashmere guardhair and its powder samples were obtained under Attenuated TotalReflectance mode using a Brucker VERTEX 70 spectrometer with aresolution of 4 cm−1 and 64 scans per sample.
2.8. XPS
The surface composition of the cashmere guard hair and its pow-der samples was investigated using a K-Alpha X-ray PhotoelectronSpectrometer (XPS) from Thermo Fischer Scientific using monochro-matic X-rays focused to a 400 μm spot size. Excessive charging of thesamples was minimised using a flood gun during XPS measurements.High resolution peak scans were performed at 20 eV pass energy. Thepeak scans were employed to obtain the elemental composition of C,O, N, and S.
3. Results and discussion
3.1. Fibre morphology
The surface morphology of cashmere guard hair is similar to finecashmere fibre with scales pointing towards the fibre tip. Both typesof fibres are cylindrical in shape. However the diameter of cashmereguard hair fibres is much larger than their downy undercoat counter-parts (Fig. 1a and b). Unlike the fine cashmere fibres, the guard hairsdo not have crimp or curvature (Fig. 1d). Due to their large diameterand the lack of crimp, the cashmere guard hairs are unsuitable forspinning into yarns for traditional textile applications.
Fig. 1. SEM image of a. cashmere guard hair; b. cashmere fibre; c. cashmere guard hair croscashmere fibres (right).
In the cross-sectional view, the guard hairs are found to be medul-lated and round in shape with few exceptions (Fig. 1c). Large diame-ter guard hairs have distinct medulla. Guard hairs with larger medullatend to have a collapsed and flattened cross-section [24]. A few guardhairs with much smaller diameters are nonmedullated.
SIFAN tests showed that the average diameter of individual guardhairs varied from 43 μm to 120 μm. The mean hair diameter was75.55 μm with a standard deviation of 16.9 μm. The SEM imagesagreed with the SIFAN results. Herrmann and Wortman reported amean cashmere guard hair diameter of 95.1 μm with a large standarddeviation of 25.69 [25]. On the other hand, McDonald et al. [26] found,in a three year study, that the mean guard hair diameter in cashmerefleece varied with time, depending on the month of shearing. In theirstudy, the mean guard hair diameter varied from 70 μm to 120 μm.
3.2. Fibre mechanical properties
The SIFAN measured mean tensile strength of the guard hair was0.96 cN/dtex, which is close to the reported strength of wool (1.121cN/dtex) and fine cashmere fibres (1.086–1.483 cN/dtex) [27]. Themechanical properties of cashmere guard hairs were also testedafter partial hydrolysis prior to milling. The results are presented inTable 2. The tensile properties of the guard hairs deteriorated follow-ing the partial acid hydrolysis. The guard hairs retained 38% of theirbreaking elongation and 35% of their tenacity after 10 h hydrolysiswith 1 M HCl at 80 °C. The reduction in their mechanical propertiesdue to partial acid hydrolysis was also reflected in the bending abra-sion test results. With the increase in hydrolysis time, the number ofcycles needed to break the fibres reduced. The PH10CHF fibres lastedonly 5% of the number of cycles required to break untreated fibres.
s-section; and d. digital photograph of a bunch of cashmere guard hairs (left) and fine
Table 2Change in physical properties of cashmere guard hairs on hydrolysis with 1 M HCL at80 °C for different time.
Figure in parenthesis indicates standard deviations.
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We earlier reported a significant drop in the mechanical properties ofsilk after alkali hydrolysis during silk degumming [10].
Fig. 3. SEM image of CHF-AM.
3.3. Wet attritor milling
Cashmere guard hairs with or without acid hydrolysis were wetmilled using an attritor. The mean particle size (d(0.5)) as a functionof milling time is presented in Fig. 2. As shown in Fig. 2a, the rate ofpulverisation is enhanced after partial acid hydrolysis. Partiallyhydrolysed cashmere guard hairs took around 2 h to be pulverisedinto particles with volume d(0.5) of 5 μm, while the untreatedguard hairs took at least 4 h to reach the same size. However, contin-ued milling for long hours did not further reduce the d(0.5) for all thesamples. This is consistent with our earlier results on silk where a re-duction in fibre tenacity improved milling time but could not achievefiner particles [16]. The quicker pulverisation rate of partially hydro-lysed hair samples can be attributed to the significant reduction instrength and elongation of fibres.
Fig. 2. (a) Effect of acid hydrolysis on the particle size reduction rate during wet attritormilling of cashmere guard hair, (b) and particle size reduction rate of cashmere guardhair in comparison with silk and wool during wet attritor milling.
To compare the milling behaviour of cashmere guard hair withother animal fibres, wool milling was also performed under similarconditions. Silk milling results are reproduced from a published liter-ature [16]. As shown in Fig. 2b, silk and wool follow a similar particlesize reduction rate which appears to be different to that observed forcashmere guard hair during the initial milling period (b100 min). Thedifference in the particle size at the early milling time is due to thelarger diameter of cashmere guard hairs compared to wool and silk.However, all the materials were pulverised into particles withd(0.5) of about 5 μm after about 4 h of milling with no further reduc-tion in particle size. We earlier reported a similar milling characteris-tic for silk, and attributed to the dynamics of particle fragmentationand aggregation during long milling [10].
The spray dried particles from the 6 h attritor milled slurryappeared to be globular in shape with a mushroom like structure(Fig. 3). The formation of mushroom like structure was also foundduring fracture of viscoelastic natural multifibrillar fibres [28,29]and the same mechanism may apply to cashmere guard hairs. Theshape and size of all the powder samples were similar with no signif-icant effect of partial acid hydrolysis. The particle size from the ob-served SEM images was found to be in agreement with the particlesize measurement data obtained from laser diffraction (Table 3).
3.4. Air jet milling
Air jet milling was performed on spray dried particles. As shown inTable 3, all types of spray dried particles further decreased in sizeafter air jet milling. Importantly, in the case of air jet milling, the re-duction in size was proportional to the degree of hydrolysis of thematerial. The particle size, d(0.5), decreased from 829 nm forPH4CHF-AJ to 461 nm for PH10CHF-AJ. Hence brittle and weak parti-cles could be more effectively pulverised by air jet milling, whereasattritor milling showed no difference in the particle size after acid hy-drolysis. The wet conditions during attritor milling may have hin-dered further reduction of particle size by softening the particlesallowing more collision energy to be absorbed and by encouragingaggregation. On the other hand, air jet milling in dry conditions
Table 3Particle size measurement data from laser particle size analyser.
Fig. 4. Particle size distribution. Fig. 6. BET surface area of cashmere guard hair samples and their powders (n=3).
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resulted in the breaking down of these aggregates and/or further frac-ture of primary particles. The possibility of de-aggregation as well asfurther fracture of primarily particles is supported by the formationof more irregular particles (Fig. 5). Furthermore, it was found thatthe span (η) values were also increased after air jet milling forPH4CHF-AJ and PH10CHF-AJ powder particles with skewed particlesize distribution, either having a longer left tail (finer particles) or abimodal distribution (Fig. 4). This happened due to the formation ofa large amount of sub-micron particles without further aggregationalong with the presence of micron scale particles, resulting in widerspan values (Table 3).
3.5. BET surface area
The specific surface area of cashmere guard hairs at differentstages of milling is shown in Fig. 6. The BET surface area of spraydried and air jet milled particles is compared with the respectivecashmere guard hairs.
Compared to unhydrolysed particles, the larger specific surfaceareas of spray dried hydrolysed particles suggests that hydrolysis in-duced a more porous sturcture. In addition, longer hydrolysis resultedin higher specific surface area.
After air jet milling, the BET surface area increased only slightlydespite significant differences in d(0.5) for all the hydrolysis condi-tions. This suggests that air jet milling resulted in deaggregation ofprimary particles from the porous aggregates which led to only aslight increase in surface area.
Fig. 5. SEM image of PH10CHF-AJ.
3.6. FTIR analysis
To investigate possible changes in the surface characteristics ofcashmere guard hair during milling, FTIR analysis was performed.Apart from the classical amide absorption bands, the spectrum ofcashmere guard hair (CHF) exhibited significantly strong absorptionbands at 2920 cm−1 and 2850 cm−1 (Fig. 7) which are assigned tothe C\H asymmetric and symmetric vibrations of alkyl groups[30,31]. These peaks are attributed to the presence of such bonds inthe outermost epicuticle membrane of long hydrocarbon lipid chainson the overlapping hair cuticle cells [32]. The disappearance of theseabsorption bands in the FTIR spectra of cashmere guard hair powders(CHF-AM and CHF-AJ) thus indicates the disintegration of surface cu-ticle cells and exposure of inner cortical cells on the powder surface.Similar changes in FTIR spectra were observed for partially hydro-lysed cashmere guard hairs and their powders.
The epicuticle membrane of hydrocarbon lipid chains on the haircuticle cells is known to render the hair surface hydrophobic andchemically resistant [33]. The disintegration of cashmere guard haircuticle cells, including the hydrophobic epicuticle membrane, istherefore expected to improve the absorption characteristics of pow-ders particularly towards some chemical species.
3.7. XPS analysis
The effect of milling on the surface chemistry of cashmere guardhair was studied by XPS. As evident in Table 4, the C and S contentsof the guard hair (CHF) decreased while the N and O contents
Fig. 7. Infrared spectra of cashmere guard hair and powders.
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increased on attritor milling (CHF-AM); whereas there was littlechange after the further air jet milling of the attritor milled powder(CHF-AJ). The chemical changes reflect the exposure of the N richfibre cortex by removal of S rich cuticle [34] of cashmere guard hair,resulting in the decreased S and increased N of the powder surfaces(CHF-AM and CHF-AJ). These results confirmed the earlier FTIR find-ings of the disintegration of cashmere guard hair cuticle cells and ex-posure of the cortex. The XPS results for partially hydrolysedcashmere guard hairs and their respective powders were consistentwith these findings (data not shown).
In Fig. 8a, b and c, the peak at 284.6 eV, assigned to C\C, C\H andC\S species [35], can be attributed to the hydrocarbon backbone ofcovalently bound fatty acids and the side groups of amino acids inthe case of cashmere guard hair (CHF). For the powders (CHF-AMand CHF-AJ), only the later will contribute. The peak at 288 eV(Fig. 8a) represents the amide group (\NH\CO\) of protein com-pounds [36]. Some oxidised species (C\O, O\C\O and C_O) werefound in the powder samples (CHF-AM and CHF-AJ) as per thepeaks at ~286 eV and ~287.6 eV (Fig. 8b and c) [37]. The peak corre-sponding to the amide bond (288 eV) appears to overlap the strongC_O peak at 287.8 eV in the case of CHF-AJ (Fig. 8c). Furthermore,the peak at ~168 eV [38] along with the presence of disulfide bonds(peak at ~164 eV) [39] in the S2p spectra indicates the formation ofsulfonate (RSO3) species on the powder (CHF-AM and CHF-AJ) sur-face (Fig. 8e and f). The appearance of photoelectron peaks associatedwith oxidised carbon and sulphur, along with the increase in the
Fig. 8. Curve fitted C1s (a,b,c) a
relative height of these peaks, indicates that the cashmere guardhairs were oxidised during milling, possibly due to localised heat dur-ing the wet milling. The N1s and O1s spectra of the powder sampleswere similar to those for the unmilled hair with peaks at 400 eVand 531 eV respectively (results not shown).
Thus, the oxidised cashmere guard hair powder surface with its in-creased concentration of nucleophlic oxygen and nitrogen atoms,along with the disintegration of the hydrophobic surface cuticle cells,is likely to result in improved binding of reactive chemical species.
4. Conclusion
The partial acid hydrolysis of cashmere guard hairs led to a sub-stantial deterioration in mechanical properties which improved thepulverisation rate during wet attritor milling. The dynamics of parti-cle fragmentation and aggregation during prolonged attritor millingresulted in the levelling-off of particle size to an approximately con-stant volume-based mean particle size d(0.5) of about 5 μm, irrespec-tive of any acid treatment. The initial pulverisation rate of cashmereguard hair differed from those of wool and silk due to its large diam-eter. The milling of cashmere guard hair resulted in disintegration ofsurface cuticle cells and exposure of the inner cortical cells on itspowder surface along with oxidation of the powder surface. The par-tial acid hydrolysis of guard hairs assisted in achieving smaller parti-cles during dry air jet milling but not during wet attritor milling. Airjet milling broke up the porous aggregates into smaller particlesand, as a result, the BET surface area showed only a slight increase.
Acknowledgements
Funding support from the Australian Research Council (ARC) isacknowledged.
185K. Patil et al. / Powder Technology 219 (2012) 179–185
References
[1] P. Holst, W. Clarke, Skin and fleece characteristics of two groups of feral goats.Australian Journal of Experimental Agriculture and Animal Husbandry 22(116):173–6.
[2] J.P. Dubeuf, P. Morand-Fehr, R. Rubino, Situation, changes and future of goat in-dustry around the world, Small Ruminant Research 51 (2) (2004) 165–173.
[3] J. Hu, Y. Li, Y. Chang, K. Yeung, C. Yuen, Transport properties of fabrics treatedwith nano-wool fibrous materials, Colloids and Surfaces A: Physicochemical andEngineering Aspects 300 (1–2) (2007) 136–139.
[4] R. Rajkhowa, R. Naik, L. Wang, S. Smith, X. Wang, An investigation into transitionmetal ion binding properties of silk fibers and particles using radioisotopes, Jour-nal of Applied Polymer Science (2010) 3630–3639.
[5] R. Naik, G. Wen, S. Hureau, A. Uedono, X. Wang, X. Liu, et al., Metal ion bindingproperties of novel wool powders, Journal of Applied Polymer Science 115 (3)(2010) 1642–1650.
[6] T.K. Une, K. Kusaki, H. Takai, Properties of silk pigments and its use for cosmetics,Fragrance Journal 4 (2000) 15–21.
[7] X. Wang, E. Wenk, A. Matsumoto, L. Meinel, C. Li, D. Kaplan, Silk microspheres forencapsulation and controlled release, Journal of Controlled Release 117 (3)(2007) 360–370.
[8] Z. Cao, X. Chen, J. Yao, L. Huang, Z. Shao, The preparation of regenerated silk fibro-in microspheres, Soft Matter 3 (7) (2007) 910–915.
[9] J. Nam, Y. Park, Morphology of regenerated silk fibroin: effects of freezing tem-perature, alcohol addition, and molecular weight, Journal of Applied Polymer Sci-ence 81 (12) (2001) 3008–3021.
[10] R. Rajkhowa, L. Wang, X. Wang, Ultra-fine silk powder preparation through rotaryand ball milling, Powder Technology 185 (1) (2008) 87–95.
[11] W. Xu, W. Cui, W. Li, W. Guo, Development and characterizations of super-finewool powder, Powder Technology 140 (1–2) (2004) 136–140.
[12] Y. Li, W. Xu (Kowloon, HK) inventor. Apparatus for producing fine powder. 2006.[13] Y. Cheng, C. Yuen, Y. Li, S. Ku, C. Kan, J. Hu, Characterization of nanoscale wool
particles, Journal of Applied Polymer Science 104 (2) (2007) 803–808.[14] T. Miyamoto, T. Amiya, H. Inagaki, Preparation of wool powder by explosive puff-
ing treatment, Kobunshi Ronbunshu 39 (11) (1982) 679–685.[15] K. Joko, Preparation of wool powder by the different mechanically methods, Sen'i
Gakkaishi 59 (1) (2003) 30–34.[16] R. Rajkhowa, L. Wang, J. Kanwar, X. Wang, Fabrication of ultrafine powder from
eri silk through attritor and jet milling, Powder Technology 191 (1–2) (2009)155–163.
[17] A. Peterson, S. Gherardi, Measurement of cashmere yield andmean fibre diameterusing the optical fibre diameter analyser, Australian Journal of Experimental Ag-riculture 36 (4) (1996) 429–435.
[18] B. Restall, W. Pattie, The inheritance of cashmere in Australian goats. 1. Character-istics of the base population and the effects of environmental factors, LivestockProduction Science 21 (2) (1989) 157–172.
[19] D. Tester, Fine structure of cashmere and superfine merino wool fibers, TextileResearch Journal 57 (4) (1987) 213.
[20] B. McGregor, R. Postle, Processing and quality of cashmere tops for ultrafine woolworsted blend fabrics, International Journal of Clothing Science and Technology16 (1/2) (2004) 119–131.
[21] C. Vineis, A. Aluigi, C. Tonin, Morphology and thermal behaviour of textile fibresfrom the hair of domestic and wild goat species, AUTEX Research Journal 8 (3)(2008) 68–71.
[22] E. Előd, H. Nowotny, H. Zahn, Action of hydrochloric acid on wool keratin, MelliandTextilber 23 (1942).
[23] GEA Niro Method No. A 8 d, , September 2005.[24] D. Allain, J. Roguet, Genetic and non-genetic variability of OFDA-medullated fibre
contents and other fleece traits in the French Angora goats, Small Ruminant Re-search 65 (3) (2006) 217–222.
[25] S. Herrmann, F. Wortmann, Opportunities for the simultaneous estimation of es-sential fleece parameters in raw Cashmere fleeces, Livestock Production Science48 (1) (1997) 1–12.
[26] B. McDonald, W. Hoey, P. Hopkins, Cyclical fleece growth in cashmere goats,Australian Journal of Agricultural Research 38 (3) (1987) 597–609.
[27] F. Rocco, G. Maurizio, Yarn strength prediction: a practical model based on artifi-cial neural networks, Advances in Mechanical Engineering 2010 (2010).
[28] J.W.S. Hearle, B. Lomas, W.D. Cooks, Atlas of fibre fracture and damage to textiles,second ed., Woodhead, 1998.
[29] K. Sen, M. Babu, Studies on Indian silk. I. Macrocharacterization and analysis ofamino acid composition, Journal of Applied Polymer Science 92 (2004)1080–1097.
[30] P. Garidel, Mid-FTIR-microspectroscopy of stratum corneum single cells and stra-tum corneum tissue, Physical Chemistry Chemical Physics 4 (22) (2002)5671–5677.
[31] P. Garidel, A. Blume, W. Hübner, A Fourier transform infrared spectroscopic studyof the interaction of alkaline earth cations with the negatively charged phospho-lipid 1, 2-dimyristoyl-sn-glycero-3-phosphoglycerol, Biochimica et BiophysicaActa (BBA)-Biomembranes 1466 (1–2) (2000) 245–259.
[32] J. Rippon, The structure of wool, Wool Dyeing 51 (1992).[33] J. Leeder, J. Rippon, Changes induced in the properties of wool by specific epicu-
ticle modification, Journal of the Society of Dyers and Colourists 101 (1) (1985)11–16.
[34] C.M. Carr, I.H. Leaver, A.E. Hughes, X-ray photoelectron spectroscopic study of thewool fiber surface, Textile Research Journal 56 (7) (1986) 457.
[35] N. Brack, R. Lamb, D. Pham, P. Turner, XPS and SIMS investigation of covalentlybound lipid on the wool fibre surface, Surface and Interface Analysis 24 (10)(1996) 704–710.
[36] M. Mori, N. Inagaki, Relationship between anti-felting properties and physico-chemical properties of wool fibers treated with Ar-plasma, Textile Research Jour-nal 76 (9) (2006) 687.
[37] X. Dai, F. Elms, G. George, Mechanism for the plasma oxidation of wool fiber sur-faces from XPS studies of self assembled monolayers, Journal of Applied PolymerScience 80 (9) (2001) 1461–1469.
[38] C. Wagner, W. Riggs, L. Davis, Handbook of X-Ray Photoelectron Spectroscopy,Perkin-Elmer Corporation, 1979.
[39] M.M.Millard, A.E. Pavlath, Surface analysis of wool fibers and fiber coatings by x-rayphotoelectron spectroscopy, Textile Research Journal 42 (8) (1972) 460.
