Evaluation of Shittori Characteristic for Fabrics

Transcription

1 ORIGINAL PAPER Journal of Textile Engineering (2008), Vol.54, No.3, The Textile Machinery Society of Japan Evaluation of Shittori Characteristic for Fabrics TANAKA Yukari a,*, SUKIGARA Sachiko b a Mukogawa Women s University, 6-46 Ikebiraki-cho, Nishinomiya-city, Hyogo , Japan b Department of Advanced Fibro Science, Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto , Japan Received 7 December 2007; accepted for publication 20 May 2008 Abstract Shittori in Japanese word of the human tactile sensation was not the same as smoothness. We evaluated the shittori feeling for fabrics by the sensory evaluation such as Kendall s rank method, Scheffe s method of paired comparison (modified method by Nakaya), and analyzed the relationship between the results by sensory evaluation and the mechanical, surface and thermal properties of fabrics measured by the KES system. The stronger shittori sensation for fabrics was accompanied with either the warm or soft. The yarn count and yarn density were related to the intensity of shittori. The effective characteristic values to understand shittori feeling of fabrics were q max (the maximum value of heat flux), MIU (coefficient of friction), 2HB (hysteresis of bending moment), WC (compression energy) and thickness. In the cosmetics field, shittori expresses such state as the moisture is maintained in the skin, however in the case of shittori for fabrics, moisture regain of fabrics did not affect the subjective evaluation of shittori. Key Words: Shittori, Tactile sensation, Objective evaluation, Sensory evaluation 1. Introduction Shittori in Japanese word describes the unique feeling, which can be related to the human tactile sensation. Shittori is commonly used as the cosmetics field when human s skin can maintain adequate moisture. For this purpose, a lotion contains ethyl alcohol, humectants, perfume, and purified water as basis ingredients. The degree of shittori can be produced by the combination of each ingredient ratio. This sense is also obtained when the skin touches a fabric. We thought this tactile sensation is not the same as smoothness. And this sensation is also different from Numeri [1] of wool fabric, and an interesting sense to add the new character to the fabric hand. Numeri is slightly oily sense, but shittori is moist sense. Matsuo [2] studied shittori of shingosen fabrics in terms of hand. In his study, he discovered that a fabric with shittori had the small values of MMD and the large values of MIU. Yaida [3] reported that some chemically treated nonwoven fabrics could give consumer the similar shittori sensation. However, the clear definition of shittori has not been reported in the literature [2 4]. In this paper, we tried to analyze the shittori feeling for fabrics in terms of fabric mechanical, surface and thermal properties by using objective and subjective measurements for future characterization of fabric tactile properties. 2. Experimental 2. 1 Samples * Corresponding author: yukari16@mukogawa-u.ac.jp, Tel/Fax: Assuming that the characteristic of shittori in a fabric includes the smoothness, then we chose subjectively smooth 9 fabrics commonly used for lady s thin dress. The purpose of this study is to obtain the direction in characterization of the shittori sensation for fabrics. The systematic study can be the next procedure to predict the shittori feeling as one of the characteristic parameter for fabric hand. One non woven fabric that is artificial leather, was also chosen for the comparison purpose. Details of the samples were listed in Table Physical properties of fabrics We measured shear, bending, compression and surface properties by using the KES system [1, 5]. The maximum value of heat flux, q max [6], which is the indication of warm/cool feeling was also measured. Characteristic values and testing condition are listed in Table 2. 75

2 TANAKA Yukari, SUKIGARA Sachiko Table 1 Samples. Table 2 Characteristic values of basic mechanical properties and conditions of measurement Subjective hand evaluation In the preliminary experiment, subjects carried out hand evaluation according to the semantic differential scales of soft-hard, slippery-sticky, smooth- rough, low elastic-high elastic, cool-warm and also intensity of shittori. We discovered that shittori was obscure word for subjects. Following experiments, we defined shittori sensation was similar to that human s skin could maintain adequate moisture. 38 college female students judged samples in the early spring of Firstly, we explained the definition of shittori to subjects. The room temperature was 23 C and 60%RH. All samples were placed in this test, this condition more than 24 hours before this test. Subjects were asked to manipulate samples as follows; the thumb put the fabric surface, and other fingers put the fabric back, then move fingers slowly. We measured the surface temperature of a 76

3 Journal of Textile Engineering (2008), Vol.54, No.3, fabric before and after fingers touched the fabric by using the thermography (NEC, TH6200R). It was confirmed that the surface temperature increased in touch, but went back to the room temperature after 25 seconds removal of the finger. Based on this observation, the sample was placed a few minutes between each subject handled fabric sample. Subjective evaluation was carried out twice by the following two methods. Test 1: Kendall s rank method [7] was used to arrange 9 samples from the strongest sensation of shittori to lower level. Test 2: Subjects compared 4 samples as the degree of softness, warmth, shittori by Scheffe s method of paired comparison (modified method by Nakaya) [8], thus the effect of sample order on the evaluation evaluate was ignored. Four samples of different fiber type were used for this method on the basis of Test 1 results. 3. Results and discussion 3. 1 Surface properties Table 3 shows surface properties of samples. In the values of MMD, sample E shows larger value compared to other samples. This sample is a crepe fabric which surface is highly crinkled. The others have small values of MMD compared to the standard lady s thin dress fabrics [9]. The values of geometrical surface roughness (SMD) for all samples are in the range of 1.0 to 3.3. samples such as H, I, D, F for the following Scheffe s method of paired comparison test. Considering the results shown in Table 4, sample H was chosen as the highest lank of shittori among these samples. As the lowest sensation of shittori fabrics, sample F was selected instead of sample E. Because subjects did not felt shittori for sample E. Artificial leather (sample I) was chosen to find the effect of surface fine fibers on shittori. Table Test 2 Subjective evaluation of shittori ranking based on rank method. All subjective values were statistically analyzed. The main effects of shittori, warmth and softness were all significant at the 1% level. Figure 1 shows the difference between samples for three evaluations shittori, warmth, and softness. In the case of shittori, differences between samples for all combinations of pair were found to be significant at the 5% level. In the case of warmth, significant differences between sample F and I, F and H, D and H, D and I were observed at the 5% level, and other comparison results were not significant. The significant differences in subjective values of softness between Table 3 Surface properties of samples Subjective evaluation Test 1 Table 4 shows that the intensity of shittori ranking based on Kendall s rank method. A significant difference in subjective values among the samples was observed at the 5% level in Kendall s coefficient of concordance. The most strong sensation of shittori was obtained by sample H. Samples such as H, I, C, B showed the higher sensation of shittori. The surface of these samples were raised from the basic structure, thus these fine fibers on the surface might increase the sensation of shittori. In this Table, we used 4 Fig. 1 Subjective evaluation of shittori, warmth and softness. 5% significant 77

4 TANAKA Yukari, SUKIGARA Sachiko sample D and H, D and I, F and I, F and H, H and I were observed at the 5% level, and between sample D and F was not significant. In this Figure, the order of intensity in shittori and softness was agreed to result of shittori obtained by the Kendall s rank method. In Fig.2, values of main effect of shittori are plotted against those of warmth. As shown in this figure, stronger shittori sensation also accompanied with the warmer sensation. In Fig.3, values of main effect shittori are plotted against those of softness. Subjects also felt more shittori sensation as well as softness sensation Relationship between subjective and objective evaluation Fig. 2 Fig. 3 Plots of main effect values of shittori against warmth obtained from Test 2. Plots of main effect values of shittori against softness obtained from Test 2. We examined the relation between all characteristic values measured as shown in Table 2 and subjective evaluation values of shittori. A value of q max is closely related to the warm/cool sensation when a finger touches the fabric surface. Values of q max, MIU and WC were plotted according to subjective values of main effect of shittori in Fig.4. Significant differences between samples H and I and also samples D and F were not observed in main effect of shittori as shown in Fig.1. In this Fig. 4, fabrics with stronger shittori feeling such as samples H and I have smaller values of q max than those of samples D and F. The same tendency was also shown in the relationship between warmth and shittori in Fig.2. Sample I is the artificial leather which surface is covered by fine micro fibers. The values of q max for this sample is smaller than those of other fabrics. Therefore q max can be one of the parameters, which influences the shittori sensation. In respect to MIU and WC, the stronger shittori feeling of fabrics derived from large values of MIU and WC. Parameter MIU might represent the adhesion resistance Fig. 4 Values of main effect of shittori are plotted against values of q max, MIU and WC. 78

5 Journal of Textile Engineering (2008), Vol.54, No.3, to the finger. It is interesting to see that for stimulating shittori sensation, the friction can also be necessary. Compression energy (WC) is related to how much a fabric is compressed under the constant pressure that is reflected in the soft sensation against fabric. In addition, thick samples such as H and I and G have stronger shittori feeling of fabrics than other samples. If subjects detected softness resulted from compression energy and thickness during evaluation, WC and thickness are also parameter to describe shittori. The relationship between shittori feeling of fabrics and values of 2HB and B are also investigated. In respect to bending rigidity, B, subjects did not bend samples during evaluation that can be reflected in these results. Values of G and 2HG for all samples were plotted according to the shittori ranking in Fig.5. Large values of G and 2HG were obtained for the sample as H and I. In general, on increase in bending rigidity (B), shear rigidity (G) and shear hysteresis (2HG) decreases the softness of a fabric. As shown in Fig.3, stronger shittori sensation also accompanied with soft sensation. The discrepancy was obtained in this Figure. According to our evaluation method of fabrics, the soft sensation was derived from softness in compression. It is reported [1] that the hand evaluation of numeri was largely influenced by both surface and compression properties. The contribution of bending, tensile and shear parameters to numeri was small. In the case of shittori in this study, surface and compression parameters are also important to characterize the shittori sensation. In Fig.6, values of q max for all samples were plotted according to the shittori ranking. The surface of sample E is very irregular and takes much air and generated low value of q max. The regression analysis was carried out to investigate the relationship of q max to shittori between two parameters and shown as the dotted line. The intensity of shittori tends to decrease with the increase of q max value. For lower rank of shittori, further increase of q max was not observed. It is confirmed that q max can be one of the parameters which influenced the shittori sensation from results of both in rank and paired comparison methods. Fabric surface properties were influenced by fabric structure. Effect of yarn count and yarn density of woven Fig. 5 Subjective evaluation of shittori ranking based on the rank method and values of G and 2HG. Fig. 6 Subjective evaluation of shittori ranking based on the rank method and q max.... regression curve (R = 0.711) 79

6 TANAKA Yukari, SUKIGARA Sachiko Fig. 7 Subjective evaluation of shittori ranking based on the rank method and yarn count.... regression curve (R = 0.724) Fig. 9 Moisture regain of samples against the subjective evaluation of shittori in strong order. was not clear because various structure of fabrics were used as samples. In this study, shittori was described as the sensation similar to that human skin can maintain adequate moisture. The moisture regain of a fabric was measured and plotted against the subjective evaluation of shittori ranking as shown in Fig.9. In the case of cosmetics, shittori is the condition that human s skin keeps much moisture. In this Figure, both samples H and I have small values of moisture regain but were evaluated as the high rank of shittori. Samples made from silk (sample E and F) and Promix (sample D) were judged as lower shittori sensation. From these results, the moisture in fabrics does not affect subjective evaluation of shittori. The results also indicated the possibility to create the shittori sensation from the hydrophobic fibers. 4. Conclusions Fig. 8 Subjective evaluation of shittori ranking based on the rank method and yarn density.... regression curve (R = 0.593) fabrics on subjective evaluation of shittori ranking are shown in Fig.7 and Fig.8, respectively. The lower yarn count as well as high yarn density generated stronger shittori feeling of fabrics. The air resistance of fabrics can detect the air transfer through spaces between fiber and yarns. However it was not obtained the clear tendency for shittori. Shittori can be influenced not only by yarn count and yarn density but also fiber type. However the effect of fiber type on the subjective evaluation of shittori We analyzed the shittori feeling for fabrics by using objective and subjective measurements. Following conclusions were obtained: 1) Subjects felt the stronger shittori sensation for fabrics as well as the warm and soft sensation. 2) The effective characteristic values to understand the shittori feeling of fabrics were q max, MIU, WC and thickness. These parameters were related to the warm and soft sensation obtained by subjective test. 3) Subjects felt the stronger shittori feeling of fabrics, which have lower yarn count and larger value of yarn density in this study. 4) Fine fibers cover the fabric surface influenced the 80

7 Journal of Textile Engineering (2008), Vol.54, No.3, intensity of shittori feeling of fabrics. This study provided the overview of the shittori sensation of fabrics. A further systematic study is necessary to investigate the effect of fiber type and structure on the shittori to make clear the origin to generate this sensation. This work was supported in part by a Grant-in-Aid for Scientific Research (project C: ) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. References [1] Kawabata S (1980) The Standardization and Analysis of Hand Evaluation, 2nd ed., Hand Evaluation and Standardization Committee, Textile Machinery Society of Japan, Osaka [2] Matsuo T (1998) J Text Mach Soc Japan, 51, P219 P224 [3] Yaida O (2007) Prepr of Annual Conference, Jpn Res Assn Text End-Uses, June, Tokyo, 9 10 [4] Yanaka M (2008) J Jpn Res Assn Text End-Uses, 49, [5] Niwa M, ed (1997) Apparel Science, Asakura [6] Kawabata S (1984) J Text Mach Soc Japan (predecessor journal of J Text Eng), 37, T130 T141 [7] Noro A (1987) Sensory Evaluation Guide Book, pp , Japan Standard Association [8] Noro A (1987) Sensory Evaluation Guide Book, pp , Japan Standard Association [9] Niwa M, ed (1997) Apparel Science, p110, Asakura 81