Kenyan Wool Fiber Properties Sampled from Different Sheep Body Parts

WANG Hua ( ), MEMON Samiullah， MEMON Hafeezullah

1 College of Textiles， Donghua University， Shanghai 201620， China2 Donghua University Center for Civil Aviation Composites， Donghua University， Shanghai 201620， China3 Key Laboratory of Textile Science & Technology， Ministry of Education， College of Textiles， Donghua University， Shanghai 201620， China

Abstract: This study provides information on fleece characteristics for stakeholders in a wool trade to make sheep farming more viable and profitable for farmers. Wool fiber samples were taken from four sheep body parts of the 95 sheep. Tests were conducted to analyze the fiber diameter， length， color， and strength. Correspondingly， fiber surface morphology and the medullated fibers were also analyzed and the results were reported. The fiber characteristics from the shoulder and flank were better than those shorn from back and belly/legs. From the results， the values of the measured parameters suggest potential for improvement of economical qualities and in fostering the economic and industrial development

Key words: Kenya； wool； sheep； body parts

Introduction

The production of wool in the year 2013， in the world， is estimated to be about 1.2 million tons[1]which leads to the generation of a sum up to the US $80 billion from retail sales of wool products. This is produced by a great population of more than one billion sheep worldwide[2]. In the European Union (EU) only， there are numerous manufacturing companies using wool as its raw material. These industries， therefore， provide many people with job opportunities. Moreover， wool has demonstrated great potential in developing novel sophisticated products. Its structure is complex that makes the mater have unique properties such as breathability[3]， dyeing[4-5]， printing[6]， flame retardant[7-8]and absorbing unhealthy chemicals[9]. Moreover， recently it has been studied for advanced applications, such as supercapacitors[10]， conductive textiles[11]， and bio-composites[12]. Thus， it emphasizes the importance of studying wool fiber properties obtained by sheep.

Kenya possesses a great number of grass species and the difference in photosynthetic systems represents a general difference in plant growth form and distribution of pasture[13]. Fibers are known to be affected by various factors such as environment， nutrition， and animal husbandry[14]. Phosphorus， nitrogen and sulfur and other minerals in pasture also contribute to low sulfur and protein in wool fibers which in turn affects its properties[15-16]. Also， variations in the characteristics of the raw wool in each batch are found among breeds， flocks， fleeces within flocks， positions within fleeces， staples within positions， fibers within staples and along the fibers[17].

Wool is an important product on sheep ranches and farms and therefore it should be an objective of every sheep producer to produce high-quality wool so as to achieve the related financial benefits[18]. This potential can be realized if one familiarizes with the main factors affecting wool value. The system of processes to assess and classify wool fleece has been established over the years and therefore they are readily available to be applied[19-20]. The characteristics of current breeds reared in various regions and provinces in Kenya vary due to the environmental climatic conditions that the breeds are adapted to. Body condition scoring of sheep was first developed as a technique in the 1960s and later was further studied in 1984[21]. Recently， the wool fiber properties sampled from different sheep breeds of Tunisia were studied and it was found that the breed was the most important factor in the determination of wool fiber properties[22-23].

The woolen textile industry of country has a greater challenge for last few decades[24-25]. The high potential areas for wool sheep breeds are in the highlands， and therefore， Kenya should also think about the global marketing strategies to export the textile products (i.e. particularly wool and woolen goods). Scobie and his coworkers have reviewed and compared the variations in wool fiber properties due to a location on the body of sheep[26]. This paper also discusses the properties of wool fiber taken from different body parts of sheep. In this paper， the properties of wool fibers sourced from farms in Kenya were tested and analyzed.

1 Experimental

1.1 Materials

The schematic diagram of wool fleece from various sheep body parts is presented in Fig. 1. The wool shorn from flanks were labelled as RBS， those shorn from back area labeled as BCK， wool shorn from belly and legs were labeled as BLS and wool shorn from the shoulder as SHR.

Fig.1 Schematic diagram of wool fleece from various sheep body parts

Fleece weight (FW) of each sheep was measured by scale balance and recorded. The collected samples were then transferred for fiber testing.

1.2 Testing conditions

The testing conditions were identical to our previous work published[27]. The wool fibers samples scoured with eco-nonionic detergent X100 were placed in a standard temperature of 20±2 ℃ and humidity of (65±2) % environment for 24 h before the experiment to be conditioned to obtain moisture balance and then reserved in dry sample bags for testing.

1.3 Characterization

The fiber length was determined by Almeter fiber length & CVH Tester (AL100) by USTER technologies. The IWTO-17-04 was used to determine the fiber length characteristics of the wool. The length Hauteur (HFL)， Barbe (BFL) and coefficient of variation (CV) of fiber length were then obtained. The fiber length characteristics were also measured using: “ASTM D519-04-Standard Test Method for Length of Fiber in Wool Top”[28].

The fiber fineness (diameter) was determined by Laserscan Fiber Diameter Analyzer (Sirolan-laserscan) by ITEC Innovation Ltd with the accuracy of ±0.01 μm. The Laserscan， as stipulated in “International Wool Textile Organization Specifications of Test Methods， Laserscan Fiber Diameter， IWTO-12-08” was used and the Mean fiber diameter (MFD) and the coefficient of variation of fiber diameter (CVFD) were obtained for each sample.

The fiber strength was determined by Electronic Single Fiber Strength Tester (TB400C) by TESTEX Testing Equipment (Dongguan) Ltd with the resolution of ±0.01 cN and elongation accuracy of ±0.01 mm. Wool defects were analyzed by Wool defect detector (TYT/QT-114) by Metalltechnik Krapf GmbH Germany. The measurement of the color of raw wool was done using an Electronic laboratory Colorimeter (WSC-S) by Shanghai Yanhe Instrument Equipment Co.， Ltd. China as described in the test method IWTO-56-03. It was measured in terms of the reflectance intensity and expressed as whiteness indexW(%).

The fiber surface morphology of Kenyan wool fibers was analyzed by Scanning Electron Microscope TM3000 Hitachi with a magnification of 20-30000 times. Wool Fiber Stapling Apparatus Y131 Hefei Fan yuan Instrument Co.， Ltd. Comb space: 10mm.

The visual subjectively and benzol test were used to determine medullated fibers (MF).

2 Results and Discussion

2.1 Tensile strength

The testing results， curves， and data displayed were recorded through a connected computer. The BLS had the highest breaking strength of 10.17 cN which could be due to the presence of good fibers from the neck area. Thus the strength (tenacity) of the Kenyan wool is between Iranian wool (i.e. 12.2 cN/tex)[29]and Turkish wool (i.e. 9.5 cN/tex)[30]. However， it has much lower tensile strength (tenacity) than the New Zealand wool (i.e. 41 cN/tex)[31].

The RBS had the highest elongation at break value of 35.41%. The SHR had the highest yield length value of 1.13 mm which indicates that it had good elasticity although it had the lowest initial modulus value of 0.11 cN/mm. The results in Table 1 showed that the tensile properties of the wool shorn from the flank were better than the wool shorn from the other body parts， although not in all parameters. The wool tensile properties were further presented in Fig. 2.

It is clear that the integral areas of the curves in RBS wool， that is， wool shorn from the flank， were bigger than the integral areas of curves in the other graphs of wool shorn from other sheep body parts. Therefore， it can be concluded that the tensile properties of wool shorn from flank are better.

Table 1 Average values of tensile properties of the wool samples

Fig.2 Strength-elongation curves for (a) BCK， (b) RBS， (c) BLS and (d) SHR samples

2.2 Fiber length

The length Almeter， as per the IWTO-17-04 was used to determine the fiber length characteristics of the wool. Several instruments are available for measuring and expressing the length of wool fibers. IWTO lists five methods that may give rise to different results but only two are now full test methods. The fiber characteristics were also measured using “ASTM D 519 - 04 ―Standard Test Method for Length of Fiber in Wool Top” test method[28].

The methods are used depending on the method of sample preparation and how much tension is applied to the individual fibers during preparation and measurement. The results from Table 2 show that SHR samples had the longest fibers while BLS samples had the shortest. This is in harmony with fact that BLS includes fibers shorn from the legs and the neck area. Also， the CV% was lowest in SHR thus this means that there is less length variation of fibers. The fiber length and other related parameters are given in Table 2 of the samples tested using Almeter.

Table 2 Fiber lengths of the samples tested using Almeter (values are presented in mm)

The fiber length and length distribution acceptance specifications can be formed by the user. This can be accomplished by using the type of yarn-making equipment used and the anticipated end uses. The weight or mass of fibers， in the definite length increments， is determined for each or group of specimens forming one sample. The data acquired can then be used in calculating the weight-biased average fiber length as well as the weight-biased distribution. Figure 3 illustrates the length distribution in a given lot of wool fibers.

Fig.3 Mass of fiber sample in the definite length increments

The values of the fiber length Hauteur (H) and Barbe (B) were determined using the ASTM 519-4 method and are given in Table 3.

Table 3 Fiber lengths of the samples tested using

The results can be shown by plotting a cumulative weight average length frequency curve. The knowledge of the average fiber length and the distribution of fibers are significant in fiber further processing. Test Method D 519-4 for wool top testing is recommended for acceptance testing of commercial shipments. This is because it has been used widely in the trade and the current approximations of the between-laboratory accuracies are satisfactory. Cumulative length frequency distribution curves of SHR， BCK， BLS， and RBS wool tested samples are given in Fig. 4.

The curves generally showed normal cumulative length distribution of fibers. The curve for the fibers shorn from belly/legs had a shorter mean length more than all the other samples and therefore it is important to be separated during shearing and to avoid mixing with the rest of the fleece since shorter length fibers contribute more challenges during processing. The higher the coefficient of Variation， CV%， and the greater the variability in lengths between individual staples measured.

(a)

(b)

(c)

(d)

2.3 Color

The measurement of the color of raw wool was done using a laboratory Colorimeter as described in the test method IWTO-56-03. It was measured in terms of the reflectance intensity and expressed as whiteness index (W%)， as described in our previous research[32]and are presented in Fig. 5. The results showed that wool from Flank， BLS， had a poorer color than all the other samples. Our results agree with Sumneretal.[33]and Bighametal.[34]that Belly wool is often found yellower than fleece wool. Also， the wool from sheep’s back， BCK， had a poor color. Wool color is related to suint content， modified by temperature， humidity， rainfall， and sheep breed.

Fig. 5 Color values of the wool samples expressed as whiteness index percentage

The classified whiteness index value of crossbred wool should be greater than 61%， the tested samples fall well into this category since their whiteness indexes were greater than 74%.

2.4 Fiber fineness

It has been maintained that 61% of the total profits of wool is dependent on the wool fiber diameter (WFD) variation[35-36]. The Laserscan， as stipulated in IWTO-12-08， was used to determine the wool mean fiber diameters and their coefficients of variation. Nowadays the fiber fineness may also be analyzed by image processing[37]， however， this was beyond the scope of this research. These were given below in Table 4.

The fibers of fine crossbred wool fall in the category with a micrometer range of 20μm to 28μm. The wool used in this study can， therefore， be classified as fine crossbred wool since the fiber fineness ranged between 22.10 μm to 25.30 μm. The higher the CV， the greater the variability in diameter (micron) between individual staples measured. The mean fiber diameter of the samples tested had less than the carpet wool diameter and therefore， the results of this study showed a good capacity of breeds for wool production though they can still be improved by sensitizing farmers on possible benefits of wool.

Table 4 Fiber fineness of the samples and medullated and dark fibers

2.5 Medullated and dark fibers

The medullated fibers have a central channel referred to medulla with cellular remnants and air spaces. In the medullated wool fibers， the central core is hollow[38].

They can be continuous or discontinuous along the fiber and also appear dark under the light microscope. Due to this internal medulla， they continue to reflect incident light in such a way that against a black background they appear white. CSIRO developed an efficient and safe process in which an industrial solvent Benzyl alcohol is used[39]. This solvent has a refractive index of 1.540 and the white wool fibers become effectively transparent when immersed in this solvent. Through this method， the examination of larger samples is facilitated and also， they can be examined using a modified version of the existing dark fiber detector. The results of the medullated and dark fiber test are shown in Table 4.

Both dark and medullated fibers (DMF) cause problems for the manufacturer. A single dark fiber (DF) in white/pastel fabric shows as a thin dark line or as a dark smudge. In colored fabrics， medullated fibers (MF) give a different， often white， appearance when dyed. As a commercial rule of thumb， the limit for white/pastel end uses is less than 100 dark fibers per kilogram (df/kg) top， with lower limits for ultra-high quality (less than 50 df/kg) and it‘s also recommended that similar limits can be applied to Medullated Fibers in tops. The results in this study show that the wool shorn from flanks， shoulders， lower neck， and hips (RBS) had the lowest number of dark fibers， that is， 3% while SHR and BCK had 12% and 10% respectively. The main contaminations were urine stain， mud and contact with other livestock with colored hair. The wool shorn from the back area， BCK， had the highest number of medullated fibers， 16% of wool while SHR had the lowest value of 6%. Most of the wool fibers from the back area are weathered and therefore this contributes to the high value of medullated fibers.

2.6 Fiber surface morphology analysis

The fiber surface morphology of wool from Kenya and other countries were analyzed using Scanning Electron Microscope and their micrographs are shown in Fig. 6. Considering the wool from Kenya， the scales on the fiber surface are well visible unbroken. The microscale and nanoscale surface morphology of the scoured wool fibers were investigated using SEM. The curves generally showed normal cumulative length distribution of fibers. The curve for the fibers shorn from belly/legs had a shorter mean length more than all the other samples and therefore it is important to be separated during shearing and to avoid mixing with the rest of the fleece since shorter length fibers contribute more challenges during processing.

(a) (b)

Wool fibers can be affected by various factors such as environment， animal husbandry， diseases， diet， and et cetera. From the micrograph of the wool surface morphology of sample in Fig. 6(b) analyzed using SEM shows some defects on the surface of wool fibers which can be difficult to process due changes in its characteristics that might have occurred. These may affect the way the fibers will respond to any chemical or physical modification.

SEM studies were performed in a TM-3000 LV Model at a maximum magnification of 2 000× and a voltage of 15 kV. The samples were gold coated before the measurement to induce conductivity. The SEM micrographs of the scoured Kenyan wool show that the fibers appear more similar to wool from other countries except for the wool from Russia in which the scales are quite different. The wool fiber surfaces were also not damaged during scouring.

4 Conclusions

Wool fiber is a multifunctional fiber and in a range of different fiber diameters， it is currently being used for conventional and nonconventional applications. With ongoing efforts to make wool more competitive alongside other fibers， there is a need to obtain a better understanding of the relationship between application and characteristics of wool properties which in turn， assist sheep breeding programs. Also， research information in the publically accessible databases can foster further research and development. The RBS had the highest elongation at break value of 35.41%. Therefore， it can be noted that the tensile properties of wool shorn from flank are better in this regard. The SHR samples had the longest fibers while BLS samples had the shortest. This is in harmony with fact that BLS includes fibers shorn from the legs and the neck area. Also， the CV was lowest in SHR thus this means that there is less length variation of fibers. The higher the CV， the greater the variability in lengths between individual staples measured. The color was measured in terms of the reflectance intensity and expressed as whiteness index (W%). The results indicated that wool from belly/legs， BLS， had the poorest color than all the other samples. Also， the wool from sheep’s back， BCK， had a poor color. Wool color is related to suint content， modified by temperature， humidity， rainfall， and sheep breed. Internationally， the classified whiteness index value of crossbred wool should be greater than 61%， the tested samples fall well into this category since their whiteness indexes were greater than 74%. The wool fibers tested and analyzed had a fiber fineness of 22.10 μm to 25.30 μm thus falls in the category of fine crossbred wool with a micrometer range of 20 μm to 28 μm. Therefore， they can be ideal for apparel such as knitwear， blankets， and upholstery. Also， the fiber characteristics vary across the body of sheep and therefore proper sorting of wool should start right from shearing of sheep.

The main contaminations were urine stain， mud and contact with other livestock with colored hair. The wool shorn from the back area， BCK， had the highest number of medullated fibers， 16% of wool while SHR had the lowest value of 6%. Most of the wool fibers from the back area were found weathered and therefore this contributes to the high value of medullated fibers. The surface morphology analyzed using SEM micrographs revealed that the wool surface was normal and could match well with other wool from different parts of the globe. Other traits suggest the potential for improvement for economic benefits. Some desirable wool characteristics like wool diameter and strength resulted in the conclusion that this wool can be used pure or blend.