Dr. Subrata Das, Professor (Fashion Technology & Abarrna Devi R, Student (Third year) (Fashion Technology)
Bannari Amman Institute of Technology, Sathyamangalam,
Erode Distt., Tamil Nadu-838401, India
The study shows that if the non-mulberry and mulberry silk yarn treated with low pressure air plasma treatment, the properties like dye uptake, wicking improved significantly. There is no significant effect of plasma treatment on tenacity and elongation on both mulberry and non mulberry degummed silk yarn. Surface morphology can also be improved in case of non-mulberry silk by modifying the rough surfaces and etch surface morphology can be achieved in case of mulberry silk.
As per the Sir William Crookes, an English Physicist (1879) ionized gas state was considered as fourth state of matters. But the word 'Plasma' was first applied to ionized gas by Dr. Irving Langmuir, an American Chemist and Physicist in the year 1929. The study carried out by Kan Chi-wai to enhance the hydrophilicity and to improve the dyeability of wool with low-temperature plasma treatment. The hydrophilicity, dyeing and finishing processes was improved significantly in case of wool fibres. Over the last decades, surface modification of the polymers and textile has been carried out for different industrial applications such as technical textile, adhesion, packaging, thin films, biomaterials, and functional coatings. Among the available surface modification techniques, plasma technology provides an advantage that it does not damage or alter the bulk properties of the materials and keep environmental pollution in control, as it is dry finishing. The main aim of this study is to investigate the effect of low pressure air plasma treatment on different properties of silk.
Materials and method
Mulberry (Bombyx mori L.), Tasar (Antheraea mylitta D.), Muga (Antheraea assama Ww.) and Eri (Samia (Philosamia) ricini B.) degummed silks yarns were used for the study.
Low pressure air plasma treatment
A glow discharge generator (Show Co. Ltd., Japan) was used for the treatment of silk fibres and fabric at M/s. Bangalore Plasma Tech Pvt. Ltd., Bengalooru, India. The glow discharge apparatus was a radio-frequency etching system operation at 13.56 MHZ and using an aluminium square chamber with an internal size of 200 mm x 200 mm. The silk yarns selected for the study are dried in an oven at 40º C for 12 hours to minimize the water content in fibers before plasma treatment. Silk yarns were treated with airflow rate of 20cc/minute at room temperature under a low pressure of 0.5 mil bar. The surface morphology, dynamometric properties, wicking properties and dye uptake properties of degummed silk yarn were carried out.
Tenacity and Elongation
Tenacity and elongation tests are carried out on Instron tester (Model No. 5500R6021). Tenacity is expressed in breaking load in grams per denier of yarn. Elongation is the amount the stretch when pulled to the breaking point and expressed in percentage.
Wicking properties of plasma treated and untreated degummed silk yarns of different varieties were carried out by available standard procedure. All the varieties of plasma treated and untreated silk degummed yarns are tied to glass rod. Depending on the denier of the yarn dead weight is hanged to maintain uniform tension to the silk yarn and markings at 6 centimeter from the glass rod were marked. Color water solutions were prepared by dissolving acid dye in cold water. Then samples prepared were dipped till the markings. Duration of 20 minutes was allowed to wick the tinted liquid. Then wicked height was noted down for all the samples.
Acid dye of Red 3BN of 3 percent on the weight of the mulberry silk yarn was taken and standard solution was prepared and added in the water bath of 1:30 (material to liquor ratio). Sodium sulphate and Acetic acid of 40 percent concentration was added to water bath at 10 percent and 5 percent subsequently on the weight of the material. The silk yarns were entered in the bath at 40 degree centigrade. Again bath temperature was raised slowly to 90 degree centigrade. At this temperature 30 to 40 minutes the material was worked for uniform dye uptake. The pH of the bath was maintained at 4-6. The materials were taken out, washed in cold water thoroughly, squeezed and dried under shade.
Chromaflash color matching system
The Chromaflash Color Matching System (ASHCO Industries Ltd. India) was used to evaluate K/S value and wavelength for comparison of color strength between treated and untreated sample.
Surface Characterization (SEM)
Surface morphology of the samples was observed under scanning electron microscope (LEICA S 40 Cambridge, U.K. make) at different magnifications.
Results and discussion
The study covers four varieties of degummed silk yarn i.e. Mulberry, Tasar, Muga and Eri yarn. The comparative test results for tenacity and elongation, wicking properties are given in Table 1, 2 and color strength and surface morphology are shown in Figure 1 and 2, respectively. ANOVA of statistical analysis for tenacity & elongation and wicking properties are indicated in Table 3 and 4.
The effect of plasma treatment on mulberry and non- mulberry degummed silk yarn is not statistically significant for tenacity and elongation. However, the improvement in wicking property of degummed mulberry, tasar, muga and eri is significant after plasma treatment.
The color difference value of 1.578 was achieved in case of the plasma treated fabric followed by standard dyeing procedure.
From the Fig-1 it was found that 2 peaks were at 440 and 600 wavelength. At 440 wavelength plasma treated sample K/S value is 0.635 and minimum K/S value of 0.577 was found in case of control sample. At 600 wavelength plasma treated sample K/S value maximum of 0.754 and minimum K/S value of 0.542 in case of control sample.
Surface morphology of the untreated and 10 min plasma treated all silk substrates was observed under scanning electron microscope at different magnifications. In case of tasar, muga, eri and mulberry yarn, it can be seen from Fig. 2(a), 3(a) and 4(a) that untreated sample have sharp serrations morphology. However, in treated samples sharp serrations were minimized to a large extent are visible [Fig. 2(b), 3(b), and 4(b)]. But in case of mulberry untreated sample shown in Fig. 5(a) at 10 kX magnification shows smoother surface and in treated sample itched surface was visible (Fig. 5(b)).
There is no effect of low-pressure air plasma treatment on strength and elongation property of both mulberry and non-mulberry degummed silk yarn. Wicking properties can be improved in both mulberry and non-mulberry silk yarn by treating with plasma. The strength of the color expressed in K/S is also improved significantly. The finishing treatments like fire retardant, moisture management, stain guard, anti-bacterial etc. can be effectively imparted after air plasma treatment. The surface morphology of non-mulberry silks can be modified by removing of the sharp edges and in case of mulberry etched surface morphology can be achieved for required end use.
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