CHAPTER 7 DEVELOPMENT OF CHEMICAL BONDED NONWOVEN FABRICS MADE FROM RECLAIMED FIBERS FOR SOUND ABSORPTION BEHAVIOUR

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1 99 CHAPTER 7 DEVELOPMENT OF CHEMICAL BONDED NONWOVEN FABRICS MADE FROM RECLAIMED FIBERS FOR SOUND ABSORPTION BEHAVIOUR 7.1 INTRODUCTION Nonwoven is a kind of fabric with orientation or random arrangement of fibers bonded by means of mechanical or chemical bonding. The structure of nonwoven is three-dimensional netted and multi porous, which is very suitable for the application as sound absorption materials with its porosity, plasticity and elasticity. Besides, nonwoven has the advantages of using recycled fibers as basic raw material, many varies, simple manufacturing technology, high productivity, multiple technologies and several of applications. The garment industry having six cutting tables produces 50Kg of wastes per day. The thousands and thousands of garment and apparel industries will produce huge amount of cutting waste. These wastes are burned in sizing and processing industries, cleaning materials in workshops and burned in open area polluting the environment. In this chapter, the development of nonwovens by using the recycled fiber of cotton, polyester and cotton/polyester blend which are reclaimed from the waste of garment units and the analysis of their acoustic absorption is discussed in detail.

2 MATERIALS nt industries. Garment industries are producing the garments in a high volume, which in turn gives high volume of trimmed waste. These trimmed wastes are used as raw material to develop adhesive bonded nonwoven. This waste can be classified as cotton, polyester and cotton/polyester blended (colour and white). 7.3 METHODS The wastes from garment units are processed through the sequence of methods as shown in the Figure 7.1. The wastes are cleared well as they will contain many unwanted materials like papers, sewing thread, lining pieces, broken metal parts, buttons and other Contaminants. Cotton Raw material (Trimming waste of garment unit) Polyester Cutting machine Random carding Aero dynamic web former Adhesive spray bonding and drying Non - woven Figure 7.1 Flow chart for the method of development of chemical bonded non-woven

3 101 These contaminants are removed manually. The cleaned material can be cut into small bits with cutting machine of the garment units Web formation The fed web in this machine is opened further to achieve very thin layer of fiber, which are deposited over the circumference of the condensing cages (by the aerodynamic principle of web formation) and thus the thin fibrous layer is delivered. This web former produces 138 meters of fibrous layer per hour Method of Chemical bonding The fibrous layer from the web former is sprayed with polyvinyl acetate at a constant pressure and flow as shown in the Figure 7.2. The adhesive add on percentage is taken care to maintain at 20%. Precaution is taken to avoid excessive or lesser flow of adhesive through the sprayer. By the calendar roller pressure, the fibrous layer is converted into nonwoven fabric. Figure 7.2 Schematic representation of chemical bonding

4 Method of Drying The bonded sheets are dried through the drying chamber at C; C. The pre heated fabrics are calendared and heated again to bind the fabric according to the required thickness. The nonwovens of recycled cotton, polyester and cotton/polyester blended reclaimed from cutting waste of garment units were produced according to required samples of colour and white. The Figure shows the photograph of acoustic cotton nonwoven and polyester chemical bonded nonwoven. The samples such as white cotton (WC), colour cotton (CC), white polyester (WP), colour polyester (CP), white cotton/polyester (W C/P), colour cotton/polyester blend (C C/P) were produced. Figure colour and white chemical bonded nonwoven samples 7.4 TESTING METHODS The nonwoven samples of recycled cotton, polyester and cotton/polyester reclaimed fiber from cutting waste of garment units produced according to required samples of colour and white were tested for sound absorption and physical properties like thickness, areal density, Bulk density, porosity, air permeability and thermal conductivity with respect to the ASTM standard. The sound Absorption coefficient of the material is measured using impedance tube method based on ASTM 1050.

5 Methods of testing physical properties The standard test procedure followed for determining the physical properties of the nonwoven samples are ASTM D 5736 for thickness of the fabric, ASTM 6242 is for a real density and bulk density in grams per square meter, ASTM D 737 is for its air permeability, ASTM D standard methods are for the thermal conductivity and ASTM E for Porosity. In order to study the influence of fibre type, number of layers, areal density, porosity and air permeability on sound absorption, the samples of recycled fiber nonwoven were produced and measured with the above parameters. 7.5 RESULT AND DISCUSSION The physical properties of the adhesive bonded nonwoven of recycled cotton, polyester and cotton polyester blend fibers are measured and average values of samples are given in Table 7.1 The sample of white cotton (WP), colour cotton (CC), white polyester (WP), colour polyester (CP), white cotton/polyester (W C/P), colour cotton/polyester (C C/P) were tested according to the ASTM standard.

6 104 Table 7.1 Physical properties of Chemical Bonded Nonwoven Sample Thickness (mm) Areal density (g/ m 2 ) Bulk Density (g/cm 3 ) Porosity Air permeability (CC/S/C m 2 ) Thermal conductivity (W/mK) WC CC WP CP WC/P C C/P From the Table 7.1, it is observed that the white cotton, polyester and cotton/polyester recycled fiber nonwoven shows similar results in porosity. When the colour fibers are used the porosity is increased. This may due to the increase the thickness and areal density of the fabrics. While comparing the Air permeability of the samples, WC, CC, WP, CP, W C/P, and C C/P shows 34.5,35.6,37.8,38.9,35.9 and 36.4 CC/S/C m 2 lower values than that of their corresponding colour samples. These comparisons reveal that the increase in fiber content of the nonwovens decreases the air permeability. The air permeability results of sample W C/P and WP show 4% and 6% higher than that of WC. This may be due to the individual fiber properties and their bonding.

7 Sound absorption performance of WC, CC, WP, CP, and W C/P & C C/P S A C Frequency (Hz) Figure 7.3 Sound absorption performances of WC, CC, WP, CP, W C/P & C C/P Figure 7.3 shows the sound absorption coefficient of recycled fiber adhesive bonding nonwoven made out of cotton, polyester, and cotton/polyester blend. The evaluation has been done with the white and colour samples. From Figure 7.3 it can observe that while the frequency increases the sound absorption coefficient (SAC) of all samples WC, CC, WP, CP, W C/P, and C C/P also increases. Similarly while thickness increases the sound absorbing performance also increases. At the highest frequency of 4000 Hz, the SAC values of WC, CC, WP, CP, W C/P, and C C/P are 0.4, 0.68, 0.4, 0.65, 0.55 and The calculated average SAC values of WC, CC, WP, CP, W C/P, and C C/P which are 0.182, 0.331, 0.156, 0.312, and also reveal the same.

8 106 The performance of sample CC, CP, C C/P shows equal values from 0 to 1000 Hz; this may be due to the lower frequency, the small increase in thickness or fiber content of this nonwoven does not influence the sound absorption Influence of thickness on sound absorption The figure 7.4 shows the influence of thickness on the SAC values of colour and white samples of nonwoven. Figure 7.4 Influence of thickness on sound absorption From the figure 7.4 it is observed that the nonwoven WC, WP, W C/P which has 12 mm, 13.1mm, and 12.9mm thickness is having the average SAC of 0.15, 0.18, 0.232, whereas with the increase of 8mm, 1mm, and 2mm thickness CC,CP, C C/P shows the increase the average SAC of 0.31, 0.33, The Colour Cotton/polyester nonwoven C C/P with the thickness of 131mm results with average SAC of which is higher than WC, WP, CP, W C/P non-woven fabric. The result reveals that the increase in thickness of

9 107 the nonwoven fabric increases the sound absorption. This same trend was absorbed Sezgin Erosov et al (2009) Influence of areal density on sound absorption Areal density (g/m 2 ) Figure 7.5 Influence of areal density on sound absorption Figure 7.5 shows when there is an increase in areal density there is an increase in sound absorption coefficient for cotton, polyester and cotton polyester blend nonwovens. The coloured materials have more density than white material due to the dye molecule content in the coloured material. The Colour Cotton/polyester nonwoven C C/P with the areal density of 0.37g/m 2 results with average SAC of which is higher than WC, WP, CP, W C/P nonwoven fabric.

10 Influence of bulk density on Sound absorption Bulk density (g/cm 3 ) Figure 7.6 Influence of bulk density in Sound absorption The influence of bulk density on SAC of nonwovens is shown in the figure 7.6 which reveals that the increase in bulk density directly increases the SAC. Coloured nonwoven which has the difference in bulk density of 0.03g/cm 3 with the white nonwoven depicts 24% increases in SAC. Colour and white polyester nonwoven having the difference in bulk density of 0.08g/cm 3 with the Depicts 32% increase in mean SAC. Cotton polyester nonwoven having the difference of bulk density 0.025g/cm 3 with increases in mean SAC of Influence on air permeability on sound absorption While increasing thickness of nonwoven fabrics of recycled colour and white cotton, colour and white polyester, and colour and white cotton polyester blended, the air permeability decreases as in figure 7.7.

11 109 Air permeability (cc/s/cm 2 ) Figure 7.7 Influence on air permeability on sound absorption The figure refers the air permeability of cotton, polyester and cotton/polyester based upon the color and white samples. The deviation among the materials can be tested clearly based upon the fiber type and color type. The air permeability of the colour nonwoven is about cc/s/cm 2 with SAC of 0.31 to The graph also shows that polyester has less air permeability than cotton non-woven materials. It is clear that where the fabric density increased, the air permeability decreased due to increased resistance to air flow caused by the consolidation of the web, but also increases the short fiber content which will occupy the air voids. The CP has the highest air permeability value with the SAC of 0.33 which is greater than that of WC, CC, WP, W C/P, and C C/P.The above said results are in line with the findings of Teli,M.D et al(2007) and Surajit Sengupta(2010)

12 Influence of porosity on sound absorption Figure 7.8 Influence of porosity on sound absorption, The figure 7.8 shows the influence of porosity on sound absorption of cotton, polyester and cotton/polyester based upon the color and white samples values is , , , , and , when comparing the porosity and micro pores the micro pores satisfy the diffusion sound waves. The SAC of the porous materials where highly depending on the permeability of the materials. Less porosity and less air permeability of the samples permit the sound frequency lesser amount at low frequency level, but at higher frequency, the sound enters the fine pores and experience friction between the fibers and adhesiveness, thus performs with higher absorption of sound energy.

13 Influence of sound absorption on Thermal conductivity Figure 7.9 Influence of sound absorption on Thermal conductivity In the figure, the graphical representation shows the influence of sound absorption of the thermal conductivity.the density, thickness, fiber fineness, fiber length, porosity and applied temperature were found to have significant effect on the effective thermal conductivity. The thermal insulation values shows increasing the trend with the increase in the recycled non woven fabric weight. There is difference among the thermal conductivity for various materials. Cotton (colour and white) non-woven material and polyester (colour and white) non-woven material were assessed for thermal insulation property. The thermal conductivity for the colour polyester material is about 0.13W/mK which has SAC of 0.33 which is higher than that of the WC, CC, WP, W C/P, and C C/P Sound resistance performance of the nonwovens The chemical bonded nonwovens while tested for the sound resistance with 30dB to 70dB showed that the increase in number of layer increases the sound resistance. The average sound resistance percentage values for the three decibel values were shown in figure The nonwoven of recycled colour and white cotton, colour and white polyester and colour and white cotton

14 112 polyester blend approximately 15%, 27% and 35% sound resistance with fabric to source distance of 25cm, 50cm, and 75cm. The reclaimed fibers nonwoven of colour and white cotton, colour and white polyester and colour and white cotton, polyester blend showed approximately 17%, 33%, and 42% sound resistance with fabric to source distance of 25cm, 50cm, and 75 cm. These results also reveal that the sound resistance increases as the distance between the fabric and the source increases. Figure 7.10 Sound resistance performances of the nonwovens 7.6 Conclusion For the buildings interiors like screens and hangings acoustic absorption is important property required for textile materials. The nonwoven fabrics which were made up of cotton colour white, polyester colour white and cotton/polyester blend with different linear density were spray bonding method were tested for sound absorption (SAC) by ASTM E When comparing the influence of fiber and linear density of the fibers in white cotton on SAC, it was observed that fiber type is having no influence. All the nonwoven fabric having the similar value of SAC.

15 113 From this chapter the following conclusions were derived; The nonwoven fabric produced from C C/P reclaimed fiber exibit higher average of SAC of due to factors like fiber, yarn and fabric structural behavior. The SAC value of all the nonwoven fabrics increases with the increase in linear density For all the nonwoven fabrics when there is an increase in areal density SAC also increased. The nonwoven fabric density is having direct influence of SAC. Similar to air permeability lower level the porosity the higher level the sound absorption. The air permeability of the colour nonwoven is about cc/s/cm 2 with SAC of 0.31 to 0.36 The nonwoven fabrics produced from cotton and a polyester reclaimed fiber shows the similar values of sound absorption due to the factors like fiber, yarn and fabric structural behavior. The thermal conductivity for the colour polyester material is about 0.13W/mK which has SAC of 0.33 which is higher than that of the WC, CC, WP, W C/P, and C C/P.

16 114 The resistivity of white cotton values shows the lowest sound resistance values The finer the linear densities lower the sound resistance. The colour cotton/polyester sample performed the highest sound resistance of 64%.