Applications of silk

Because of the unique characteristics such as handle, drape, appearance, lustre, and comfort properties, silk is used in both apparels such as saris, dress, shirts, suits, pants, socks, etc., and home furnishings such as upholstery fabrics, blankets, bed sheets, etc. Moreover, as silk proteins' amino acid composition is close to that of human skin, it is also used in biomedical applications such as medical sutures, prosthetic arteries, etc.


Properties of Woven Silk Fabrics:

Silk, the strongest natural fiber, is comfortable and has good absorbency with excellent drape. In order to judge the suitability of a fiber for different end-uses such as clothing and industrial uses, it should have certain desirable properties. The study was carried out to know the physical and comfort properties of white and red eri spun silk fabrics compared with mulberry spun silk fabrics.

High fullness and softness are distinguishing properties of silk fabrics and are related to high compression deformability and tensile extensibility, which arise due to fiber crimp bulkiness. In order to clarify the effect of gap on fabric handle, the primary hands of polyester weaves having different degrees of weight reduction were evaluated objectively, and it is shown that the gap leads to higher Fukurami and Shinayakasa and lower Koshi and Hari handles of the weaves.


The study of the objective evaluation of the woven silk fabric has found that both shear stiffness and hysteresis in shear force of woven silk fabrics are extremely small in the region of relatively small strain. However, these properties become larger with increased shear strain. In the small strain region of compression and tensile properties, silk fabrics are very readily deformed as compared with fabrics made from other fibres. Analysis of the shearing properties shows that the gap between the warp and weft threads at their cross-over points in woven silk fabrics is responsible for the very low values of shear stiffness and hysteresis of shear force in these fabrics. Using shear-deformation theory and making experiments on silk fabrics prove the existence of this gap. Using strip - biaxial extension experiments and measuring the retardation strain obtain a quantitative determination of the gap. The gap observed for woven silk fabrics is 6 to 7 mm. Since microscopical observation of the cross-section of silk fabrics does not show the gap, the gap measured by mechanical methods is called an "effective" gap. The gap has a strong effect on the mechanical properties of silk fabrics, especially their shear properties; it also emphasizes the good handle of silk fabrics.


In the silk fabrics, there may be a small gap between the warp and weft threads at their cross - over points because of the sericin removing treatment that is applied after weaving. The tensile behavior of a fabric with such a gap is considered to consist of two stages. In the first stage, the bent yarn alone is stretched, since the bending rigidity of silk yarns is small, and gap is relatively large, the tensile modulus of silk fabric becomes very low in the initial tensile region. After the contact of the warp and weft threads, the soft lateral compressional property of the silk threads leads to extensibility of the silk fabric.


This stage is called here the second stage, in which the tensile and the lateral compressional deformation proportion are mainly concerned with the tensile behavior of the fabric in this region. Silk - fibroin fibre has a small fibre crimp, and this crimp also makes the silk yarn compressible. The crimp enables the silk fabric to maintain the effective gap and a stable weave structure where slight contact of fibres between the two threads supports the structure. Secondly, the crimp causes greater yarn compressibility, which leads to the higher extensibility of the weave.


The main aim of the study of the design of the fabric hand of woven silk fabric was to find method for predicting the basic mechanical properties and the hand values of both silk crepe and dress weight fabrics from selected manufacturing and finishing process parameters. As a result of joint research with the hand evaluation and standardization committee of the textile machinery society of Japan, it was possible to quantitatively determine the fundamental hand of Koshi and Tekasa (thickness and weight) which express the hand of silk fabrics by using formula derived from the characteristic mechanical property values of these fabrics. Considerable time and effort were required to measure the mechanical properties of the silk fabrics. Experience, trial and error in textile design engineering have been needed to control quality of hand of fabric.


The relationship between characteristic values (mechanical properties, hand values of silk crepe fabrics and dress weight fabrics) and the right processing factors (weave of fabric, conditions of fabric design, scouring and finishing process) has been analyzed. From the results, it is very clear that the fifteen mechanical properties related to end use performance can be adequately predicted by the eight processing factors. Hand values Koshi and Tekasa are related to these eight processing factors. In this, it is necessary to include a factor representative of form of warp and weft to increase the accuracy of prediction. These regression equations provide useful information with respect to desirable handle properties to both fabric designers and finishers.


The relationships between the hand of woven silk neckwear fabrics and consumer purchasing preferences were studied. Male and female students evaluated fabric samples with a semantic differential scale of hand and sensibility adjectives, including modern (flat and cool), classic (flat and form), character (rough and cool) and natural (rough and warm). Fabrics awarded a high purchasing preference exhibited a soft or flat touch and a modern or classic sensibility.

 

FFT obtained the spectra of these recorded sounds. KES-B measured the mechanical properties of the fabrics. Fabrics with the same fibre type showed similar spectral shapes. Some mechanical properties, fabric thickness and weight predicted the sound parameters. The Kawabata fabric evaluation system was used to distinguish the characteristics of various groups of fabrics and establish the extent to which micro denier fibres mimic those of natural fibres, especially silk.


Researchers classified 75 commercial fabrics into seven groups based on fiber content, fabric structure and finishing treatment. Ten KES-FB parameters and four fabric hand descriptors constituted the distinguishing characteristics of each group. The distinguishing characteristics of micro denier polyester fabrics included flexibility with soft feel, fullness and excellent drape. Micro denier polyester fabrics resembled silk fabrics due to their irregular cross sectional shapes, low shear and bending properties.


The relationships between a fabric's compression and mechanical properties were examined. The examination used a variety of fabrics including wool, silk, polyester and cotton. The regression constant at the third phase of the regression curve was related to the fibre material and explained the initial lateral compression modulus of fibres.


The KES-F objective measurement system was used to evaluate eight fabric groups. Classification was done on the basis of the fibre content, fabric construction and special finishing treatments. Silk was the reference for tensile, shear, bending and surface properties. Micro denier fabrics were soft and smooth, but did not have a high Kishimi hand, which is typical of silk. Fabric construction had an influence on fabric stiffness, but not on fabric hysteresis.


A comparative study of fabric characteristics was carried out by using silk fabric, as a reference, caustic reduced polyester fabrics exhibit strong silk like characteristics except in their surface properties. Shear properties and bending hysteresis appear to be the most important factors affecting the hand of the fabrics studied. Thus the KESF system is very effective in discriminating silk fabric and various other silk like polyester fibre fabric.

References:

  1. Dutta R.K., Shah A.M., (1995) A comparative study of fabric characteristics using KES-B System, ATIRA Communications on Textiles
  2. Gong R.H., Mukhopadhyaya N., (1993) Fabric objective measurement A comparative study of fabric characteristics, Journal of the Textile Institute
  3. Kariyappa, P.M.D.Rao, (2010) Physical and comfort properties of mulberry, white eri and red eri spun silk yarn woven fabrics, Man Made Text in India
  4. Kawabata S. (1985), `Direction of recent development in the objective measurements', Objective measurement application to product design and process control, Edited by Kawabata S., Postle R. and Niwa M., pp.29-32.
  5. Matsudaira M., Kawabata S., (1988) Study of the mechanical properties of woven silk fabrics Part I, Fabric mechanical properties and hand characterizing woven silk fabrics, Journal of the textile Institute
  6. Matsudaira M, Matsui M, (1992) Features of mechanical properties and fabric hand of silk weaves Journal of the Textile Institute
  7. Matsudaira M and Qin H (1995), Features and Mechanical Parameters of a fabrics compressional property, Journal of Textile Institute
  8. Na Y., Kim C., (2001), Quantifying the Handle and Sensibility of Woven Silk Fabrics, Textile Research Journal
  9. Nakata, H., Nakata. S. and Egawa M. (1986), `Design of the fabric hand of woven silk weaves', Objective measurement applications to product design and process Control Edited by Kawabata S., Postle R. and Masako Niwa, The Textile Mach. Soc. of Japan
  10. Yi E, Cho G, (2000), Fabric sound parameters and their relationship with mechanical properties, Textile Research Journal, Vol. No 9, pp. 828-837.