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What are the mechanical and thermal comfort aspects of PV blended suiting fabrics produced by using different weaves and weft counts in light weight, medium weight & heavy weight categories? Prof S B Mhetre and Archana K Karadbhajne reveal the outcome of a study on these.
Clothing has a number of functions like adornment, status, modesty & protection. To be competitive, modern clothing besides having good mechanical and technological properties and being of easy care, must possess good comfort characteristics (1). Comfort has totally replaced the durability as far as the selection of garment is concerned (2).
The comfort sensation of a fabric has multidimensional attributes and it is not possible to quantify through a single physical property. It is possible to distinguish two aspects of wear comfort of clothing: Thermo physiological wear comfort and skin sensational wear comfort
Many researchers have carried out extensive work on fabric handle properties (3-13). Thermal comfort is the factor governed by the movement of heat, moisture and air through fabric. The maintenance of thermal balance is probably the most important attribute of clothing and has drawn the attention of many textile research workers (14-18).
Efforts are being made to produce comfortable fabrics, which should satisfy three conditions, ie, good hand, possibility of making good appearance of suit and mechanical comfort for wear (19). Thus both mechanical comfort and thermal comfort characteristics of the fabric needs to be investigated to understand the physical and physiological interrelationship between the cloth and human body. The present work, therefore, is aimed at studying both mechanical and thermal comfort aspects of PV blended suiting fabrics produced by using different weaves and weft counts in light weight, medium weight and heavy weight categories.
Material and methods
Materials
Preparation of fabric samples:
All the fifteen samples of suiting fabrics were manufactured with different constructions from 65:35 polyester viscose blended yarns as shown in Table I in different weight categories. The finishing of the fabric samples was done as per the normal process sequence followed in the suiting industry.
Methods
Fabric tactile comfort properties
Handle properties of the fabrics were evaluated by measuring the fabric low-stress mechanical properties on KAWABATA Evaluation System for fabrics (KES FB). The tensile properties and shear properties were studied on KES-FB1 (tensile and shear tester). Bending properties were measured on KES-FB2 (Pure bending tester). Compressional properties were studied on KES-FB3 (Compression tester). The surface roughness and surface friction were measured on KES-FB4 (Surface tester). The primary & total hand values were calculated from sixteen mechanical properties.
Fabric thermal comfort properties
Air permeability tests were conducted on KES-F8 AP1 (Air permeability tester). Thermal insulation and moisture transport rate were determined by using the KES-F 7 (Thermo Labo II B).
Results and discussion
Tensile properties
Tensile properties of suiting fabrics are shown in Table 2. The EMT (tensile strain) value indicates low-stress extensibility and is related to crimp removal process during tensile loading. This factor affects tailorability and seam slippage. A higher value of EMT provides wear comfort but creates problems during stitching and seam pressing.
It is observed that EMT for warp is higher for all fabric samples than for weft except for sample E1. EMT values are higher for plain woven fabrics. Among all plain woven fabrics A2 has highest EMT and among all 4 end satin woven fabrics, D3 has lowest EMT.
The linearity of tensile property (LT) is indicative of wearing comfort. Lower values of LT gives higher fabric extensibility in initial strain range indicating better comfort, but the fabric dimensional stability decreases. It is seen that LT is higher for B3 & lower for C1. The tensile energy (WT) values are lower for D3 and higher for A2. The tensile Resilience (RT) indicates recovery after tensile deformation. RT is higher for A3 and lower for E1.Tensile resilience values are higher for tighter construction because of crimp removal, which leads to a better recovery in tight fabrics (3).
Shear properties
It has been observed from Table 3 that the shear rigidity (G) in higher for B3 (1/48 weft, 2/1 twill) and lower for E3 (1/48 weft, 5 end satin). The high value of shear rigidity causes difficulty in tailoring and discomfort during wearing. Shear rigidity of the fabric mainly depends upon the mobility of the warp and weft threads within the fabric. The compact structure of fabric having higher pick density gives higher shear rigidity values and hysteresis of shear.
2HG and 2HG5 indicates the hysteresis of shear force at 0.5o and 5o respectively. It is also observed from Table 3 that the hysteresis for shear is higher for B3, ie, 2/1 twill woven fabric made with 1/48 Nm as a weft yarn and lower for A3, ie, plain woven fabric made with 1/48 Nm as a weft yarn. Significant reduction in shear rigidity is observed for the 2/2 twill woven fabric than 2/1 twill woven fabric. This can be attributed to the reduction in the number of yarn interlacing of the 2/1 twill woven fabric, which would considerably bring down the frictional forces giving rise to lower shear rigidity and shear hysteresis. A similar trend is observed for the satin weave fabrics. A 5-end satin weave displayed lower shear rigidity and hysteresis (except for E2 fabric) than their corresponding 4-end satin weave fabric.
Bending properties
Bending rigidity (B) of a fabric depends upon the bending rigidity of the threads and the mobility of warp and weft threads within the fabric. Bending rigidity (B) is high for E2 & low for A2. Bending rigidity and hysteresis of bending values are higher for the fabrics with more pick density. 2HB represents the hysteresis of bending moment, which is a measure of recovery from bending deformation. Hysteresis of bending moment (2HB) is high for E2 & low for A2. Bending rigidity is one of the important mechanical property influencing the tailorability of the fabric. Increase in bending rigidity increases Koshi (Stiffness). Bending rigidity is higher in warp direction than in weft direction. The bending rigidity of yarn depends on 4th power of yarn's diameter, ie, 2nd power of yarn count. Koshi increases with yarn count.
Surface properties
The fabric surface properties are shown in Table 4. It is observed that the coefficient of friction (MIU) is higher for sample C1 (2/2 twill woven fabric made with 2/84 Nm weft yarn) and is lower for B2 (2/1 twill woven fabric made with 1/56 Nm weft yarn). The mean deviation of coefficient of friction (MMD) notes the surface smoothness as perceived while moving the fingers on the fabric surface. MMD is higher for B1 (2/1 twill woven fabric made with 2/84 Nm weft yarn) and lower for C2 (2/2 twill woven fabric made with 1/56 Nm weft yarn). Also the geometrical roughness (SMD) is higher for A1 (plain woven fabric made with 2/84 Nm weft yarn ) and lower for C2 (2/2 twill woven fabric made with 1/56 Nm weft yarn).
According to M Matsudaira et al (6) scroopy feel of fabric increases because of increase of twist number of weft yarn. All the samples of first category are made by 2/84 Nm weft yarns whose TPI is 29.79, which is more than other yarns. Thus fabric woven using finer yarns in B2 fabrics aided in improving the surface smoothness.
Compressional properties
The compressional properties of fabrics are measured by placing the sample between two plates and monitoring its thickness with increasing pressure. The linearity of compression (LC) mainly depends on the fabric thickness and compressional characteristics of the yarn. It has been observed from Table 5 that LC is higher for A1 (plain woven fabric made with 2/84 Nm weft yarn)& lower for A3 (plain woven fabric made with 1/48 Nm weft yarn). Compressional energy (WC) depends upon the LC and the amount of compression. WC is higher for E2 (5 end satin woven fabric made with 1/56 Nm weft yarn) and lower for A3 (plain woven fabric made with 1/48 Nm weft yarn). The compressional resilience (RC) mainly depends upon fabric thickness and compressional characteristics of yarn. It has been observed that RC is higher for D3 (4 end satin woven fabric made with 1/48 Nm weft yarn) and lower for E2 (5-end satin woven fabric made with 1/56 Nm weft yarn).
Fabric weight and fabric thickness
The fabric weight is higher for E2 (5 end satin woven fabric made with 1/56 Nm weft yarn) and lower for A2 (plain woven fabric made with 1/56 Nm weft yarn) and the fabric thickness is higher for E2 and lower for A2.
Fabric hand values
The fabric samples are manufactured for winter suiting, hence the three primary hand values, namely, Koshi, Numeri and Fukurami have been calculated and are shown in Table 5. Primary hand values are graded by using a scale of 1 - 10 where 1 indicates the weakest feeling and value 10 indicates the strongest with regards to the particular descriptor.
THV gives a consolidated index reflecting the suitability of the fabric for predetermined applications in a scale of 0 - 5. A THV of 5 indicates that the fabric is ideal for the intended use while a THV of 0 suggests its unsuitability. A value of THV between 0-5 would indicate varying levels of suitability of the fabric for the proposed application.
In a fabric the Koshi (stiffness) depends on its bending properties. Koshi values are higher for B3 (2/1 twill woven fabrics made with 1/48 Nm weft yarn ) and lower for A2 (plain woven fabric made with 1/56 Nm weft yarn). The KOSHI is less for A2 fabric since its bending rigidity is less. Numeri means surface smoothness. Numeri values are lower for 2/1 twill woven fabrics and higher for 5-end satin woven fabrics. It has been observed that for sample E1, Numeri value is high and for B1, the Numeri value is less.
Plain woven fabrics due to higher number of yarn interlacing, in the fabric structure presented a more uneven surface topology compared to the twill and satin weave fabrics. The long floats in the twill and satin fabrics, aided in improving the surface smoothness. It was observed that irrespective of the weave, fabrics woven using finer yarns helped in improving their surface smoothness.
Fukurami (Fullness & Softness) is the bulky, rich and well-formed feeling and it mainly depends on fabric bulk and compressional properties. It has been observed that Fukurami values are higher for 2/2 twill woven fabrics specially for C1and lower for B1, ie, 2/1 twill woven fabrics. The total hand value of the fabric is estimated from the primary hand values using Kawabata System of equations. It has been observed from Table 6 that THV are higher in the 2/2 twill and 5-end satin woven fabrics and lower in plain woven fabrics.
The 2/2 twill weave fabric gave better grading (THV) as a winter suiting fabric compared to 2/1 twill weave by virtue of higher fabric smoothness (Numeri), softness and fullness (Fukurami) and lower stiffness (Koshi).
Similarly, 5-end satin weave gave better Total Hand Value (THV) than 4-end satin weave. They also exhibit greater surface smoothness possibly due to longer floats on the fabric surface compared to 4-end satin weave. Softness and fullness too were enhanced due to greater thickness of these fabrics. Overall the 5-end satin weave fabrics were noted to give the best grading in terms of total hand value as suiting fabric among all the fabrics under study.
Fabric comfort properties
The thermal comfort is related to fabric transmission behaviour, namely, thermal insulation, moisture transport rate and air resistance. Table 5 shows the comfort properties of all the fabric samples. It has been observed that the air resistance increases for twill and satin woven fabrics. This may be attributed to compact structure of fabric and hence lesser number of pores are available for air passage. The air resistance is low for plain woven fabric A2 and high for 2/1 twill woven fabric B3. Since single yarn woven fabrics gives higher air permeability as compared to 2 ply yarns because of low packing density of single yarn (15).
Thermal insulation is an important measure for analysing the effect of material properties on heat transfer. Thermal insulation value is high for 2/2 twill woven fabric made from 2/84 Nm as weft yarns & low for 2/1 twill woven fabric made from 1/48 Nm as weft yarns. Higher the air resistance, lower is the thermal insulation value. Fabric thickness is the most important factor governing the thermal insulation.
Moisture vapour transfer is the ability of a fabric to transfer the perspiration in form of moisture vapour through it. Higher the air resistance, lower is the moisture transport. The moisture vapour transfer of 5-end satin woven fabrics are lower than plain woven fabrics, both made from 1/56 Nm as a weft yarn. Thus it is observed that the moisture vapour transport is higher for plain woven fabrics than twill and satin woven fabrics.
Conclusion
1. The extensibility in warp direction is higher than in weft for all fabric samples. Plain woven fabrics have higher extensibility.
2. Linearity of tensile property and tensile energy values are higher for plain woven and 2/1 twill woven fabrics.
3. Shear rigidity and hysteresis of shear is higher for 2/1 twill woven fabrics and it is highest for 2/1 twill woven fabrics manufactured with 1/48 Nm weft yarns. This may be because of high weave density.
4. 2/1 twill woven fabrics shows higher bending rigidity and hysteresis values and plain woven fabrics show less bending rigidity and hysteresis values.
5. Plain fabrics have more geometrical roughness than twill and satin woven fabrics.
6. Coefficient of friction of 2/1 twill woven fabrics is lower as compared to other fabrics under study.
7. Linearity of compression is higher for plain woven fabric manufactured from 2/84 Nm weft yarns and lower for fabric woven in plain weave with 1/48 Nm weft yarns. Compressional energy is higher for satin woven fabrics.
8. Fabric thickness is higher for 5-end satin woven fabrics than plain fabrics.
9. KOSHI (stiffness) values are higher for 2/1 twill and lower for plain woven fabrics.
10. Irrespective of the weave, fabrics woven using finer yarns helped in improving their surface smoothness.
11. NUMERI (smoothness) and FUKURAMI (fullness & softness) values are higher for 2/2 twill and 5-end satin, thus giving higher THV.
12. Plain woven fabrics gives lower NUMERI and FUKURAMI, thus lower THV.
13. The air resistance is more for twill and satin woven fabrics.
14. The air permeability and moisture transport rate is more for plain woven fabrics.
15. 2/2 twill woven fabrics give the highest values for thermal insulation.
References
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Note: For detailed version of this article please refer the print version of The Indian Textile Journal June 2012 issue.
Prof S B Mhetre
Department of Textile Technology,
Textile & Engineering Institute,
Ichalkaranji, Dist Kolhapur,
Maharashtra.
Ms Archana K Karadbhajne
Department of Textile Technology,
Textile & Engineering Institute,
Ichalkaranji, Dist Kolhapur,
Maharashtra.
Email: archu.lande@gmail.com.
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