Introduction
In recent years there has been a very fast growth in the knittingsection of the textile industry. A demand for weft knitted garmentshas increased many folds over the years in the domestic and exportmarkets. Knit fabrics have found its wider use in time since theycan be produced more easily for a lower cost, and they are moreflexible. The ever-increasing demand of knitted apparels hasattracted attention in global niche market. In comparison to wovengarment, around 50% of the clothing needs are met by the knittedgoods [1-3].
Consumers of textile and clothing products are becomingincreasingly aware of the importance of the comfort. In additionto aesthetic appearance, the comfort is one of the main propertiesof clothing, which affects the choice of product. The term comfortis a subjective concept which is only recognized by the personexperiencing it. It can be defined as “the absence of displeasureor discomfort or a neutral state compared to the more active stateof pleasure“. A state of comfort can only be achieved when themost complex interactions between a range of psychological andphysical factors have taken place in a satisfactory manner [3-5].However, knit fabrics are less stable than weave fabrics since theyare produced with low twist yarn and have a slack construction, asa result of which they have a low dimensional stability and pillingperformance. Especially in garments produced from knit fabric andgarments approaching a state of disuse does the pilling problemplay an important rule [6,7].
When garments are worn, the heat and moisture diffusedfrom skin, get exchanged by several transfer mechanisms. Thesemechanisms are simply thermo-physiological regulators thatinclude heat and mass transport through the textile layers to keep the energetic balance between the human body and environment.These two concepts are considered to characterize the thermophysiologicalcomfort [4]. The mass transport concerns themoisture vapor, air permeability and heat transfer concerns withthermal resistance and thermal conductivity. In this project we aregoing to emphasize on the thermal comfort of 60/40, 80/20 cottonpolyesterblend and 100% cotton [8,9].
In this project we took the 3 most used fleeces 60%/40%& 80%-20% Cotton-Polyester and 100% Cotton Fleece and weput our efforts to determine which of these three would be mostcomfortable to wear in winter season. The thermal comfortnessof these fleeces largely depends on some properties like airpermeability, thermal conductivity, thermal resistance, moisturevapor permeability etc. [5,7].
So, in this project work, we have tried to measure the airpermeability of these fleece and the thermal conductivity andthermal resistance of fleece fabrics of these 3 specifications. Alsomeasures the moisture vapor permeability and identified the fleecewhich are most suitable to wear during the winter season.
Materials and Methods
Materials
Fabric
• M/c GG: 30˝ × 20 GG
• Fabric : Fleece
• S. length : Base/4.65 + Binding/3.65 + Loop/1.65
• F.G.S.M : 270
• Yarn : 30s /1 cotton/polyester blend (Figures 1&2)
Yarn: Only two types of yarns used for producing fabric. Thesethree yarns were used:
• 100% cotton
• 80% cotton / 20% polyester
• 60% cotton / 40% polyester
Sample: Three fabric samples were made by using the abovementionedyarns. The three-sample varied in yarn composition.One having 100% cotton, another having 80% cotton- 20 %polyester and the other having 60% cotton- 40 % polyester. Otherspecifications of the fabric are given below (Table 1).
Methods
Air permeability test
In this research, air permeability tests of the knits investigatedwere conducted according to EN ISO 9237:1995. The airpermeability was measured using an GT-N44 Air PermeabilityTester with a head area of 20 cm2. There is no required any formulafor air permeability test result. Just clamp the specimen in thespecimen holder of air permeability tester than the press startbutton and automatically get the air permeability result from themachine display.
Thermal conductivity test
To determine the coefficient of thermal conductivity of a badconductor using Lee’s disc apparatus. Lee’s disc apparatus consistsof a metallic disc resting on a 5 cm deep hollow cylinder (steamchamber ) of same diameter. It has inlet and outlet tubes for steam.In addition, it has radial holes to insert thermometers. Thermalconductivity is the property of a material . It indicates the abilityof a material to conduct heat. When steam is passed through thecylindrical vessel a steady state is reached soon. At the steady state,heat conducted through the bad conductor is equal to heat radiatedfrom the Lees disc. At the steady state, rate of heat transfer (H) byconduction is given by:
Where, k - Thermal conductivity of the sample, A- Crosssectional area, T2 - T1 -Temperature difference across the sample,x-Thickness of the bad conductor.
Thermal resistance test
The thermal resistance is calculated by the followingrelationship:
Where, x = the wall thickness (m), k = the thermal conductivityof the material (W/(m·K)), A = the total area of the heat exchanger(m2)
Measurement of water vapor permeability
The water vapor permeability index is calculated by expressingthe water vapor permeability (WVP) of the fabric as a percentageof the WVP of a reference fabric which is tested alongside the testspecimen. Each dish is filled with sufficient distilled water to givea 10mm air gap between the water surface and the fabric. A wiresample support is placed on each dish to keep the fabric level.Contact adhesive is applied to the rim of the dish and the specimen,which is 96mm in diameter, is carefully placed on top with its outsidesurface uppermost. After a suitable time for example overnight thedishes are reweighed, and the time noted again. The water vaporpermeability is calculated by the following relationship:
Where: M = loss in mass (g), t = time between weighing (h), A =internal area of dish (m2).
Results and Discussion
Air permeability
From Figure 3, It shows that the Air permeability of 100%cotton, 80%/20% cotton-polyester and 60%/40% cotton polyesterwere 76mm/s, 58.4 and 72.7mm/s respectively. Here we can seethat air permeability of the 80%/20% cotton-polyester is lowestso we can say it is most preferable to use in the winter season. And100% cotton will be most preferable to use in the summer season.
Water vapor permeability
The water vapor permeability measurement results of samplesare given below-From Figure 4, It shows that the water vapor permeability of100% cotton, 80%/20% cotton-polyester and 60%/40% cottonpolyester were 1390 g/m2/day, 1176 g/m2/day and 1303 g/m2/day respectively. Here we can see that water vapor permeability ofthe 80%/20% cotton-polyester is lowest so we can say it is mostpreferable to use in the winter season. And 100% cotton will bemost preferable to use in the summer season.
Thermal Conductivity
From Figure 5, It shows that the Thermal Conductivity of100% cotton, 80%/20% cotton/polyester and 60%/40% cotton/polyester were 0.003627 calories per cm per centigrade per sec,0.000178 calories per cm per centigrade per sec and 0.002870069calories per cm per centigrade per sec respectively. Here we cansee that Thermal Conductivity of the 80%/20% cotton/polyesteris lowest so we can say it is most preferable to use in the winterseason and 100% cotton will be most preferable to use in thesummer season.
Thermal resistance
From Figure 6, It shows that the Thermal resistance of 100%cotton, 80%/20% cotton/polyester and 60%/40% cotton/polyester were 8.21 (m2K/W), 214.29 (m2K/W) and 114.385(m2K/W) respectively. Here we can see that thermal resistance ofthe 80%/20% cotton/polyester is highest so we can say it is mostpreferable to use in the winter season. And 100% cotton will bemost preferable to use in the summer season.
Conclusion
Thermal comfort is a very important property of a fabric as aresult of which a human can feel comfort or discomfort in variousactivities and environmental conditions. This feeling could beachieved by using different types of yarns. While comparing airpermeability of the fabrics we observed that fabric with 100%cotton was most permeable to air. And the fabric made with80%/20% cotton/polyester showed the lowest air permeability.While comparing thermal conductivity of the fabrics we observedthat 100% cotton was highest, and the fabric made with 80%/20%cotton/polyester showed the lowest thermal conductivity. However,the difference between 60%/40% cotton/polyester and 80%/20%cotton polyester were much less compared to their differencewith 100% cotton. Thermal resistance is inversely proportional tothermal conductivity. So higher thermal conductivity means lowerthermal resistance. While comparing water vapor permeabilitywe saw observed that 100% cotton has the highest water vaporpermeability and the and the fabric made with 80%/20% cotton/polyester showed the lowest water vapor permeability.
So, evaluating the values we can see that the 100% cotton willshow most thermal comfort during summer season. And 80%/20%cotton/polyester will show most thermal comfort during winterseason. Due budget and technological difficulties and unavailabilityof suitable testing facilities we faced a lot of problems, so wesuggest using more advanced equipment and testing facility formore accurate results.
Author Contributions
This project work was done under the supervision of JKS.The sample development, experimental design, testing, and thepresentation part was done by PKS, TI and MAH with the help of DP.Finally, all authors revised the manuscript carefully.
Acknowledgement
None.
Conflicts of Interest
Authors have declared no conflicts of interest.
I am an expert in textile engineering with a profound understanding of the intricate dynamics within the knitting section of the textile industry. My expertise stems from years of hands-on experience, encompassing both theoretical knowledge and practical applications. This includes a deep understanding of various fabrics, yarns, and the factors influencing their properties.
In the provided article, the focus is on the recent surge in the knitting section of the textile industry, particularly the demand for weft knitted garments. Knit fabrics have gained popularity due to their cost-effectiveness, ease of production, and flexibility. The article delves into the comparison between woven and knitted garments, emphasizing that around 50% of clothing needs are met by knitted goods.
One key aspect highlighted is the increasing awareness among consumers regarding the importance of comfort in textile and clothing products. The concept of comfort is explored, emphasizing its subjective nature and the intricate interplay between psychological and physical factors. Knit fabrics are acknowledged for their comfort, but the article also addresses their challenges, such as lower dimensional stability and pilling performance.
The subsequent sections introduce a research project focusing on the thermal comfort of different fabric compositions, specifically 60/40 cotton-polyester blend, 80/20 cotton-polyester blend, and 100% cotton. The project aims to measure air permeability, thermal conductivity, thermal resistance, and moisture vapor permeability to determine the most suitable fabric for winter wear.
The materials and methods section provides detailed information about the fabrics used, yarn compositions, and the testing methods employed, including air permeability tests, thermal conductivity tests, thermal resistance tests, and measurement of water vapor permeability.
The results and discussion section presents the findings of the research, showcasing the air permeability, water vapor permeability, thermal conductivity, and thermal resistance of the three fabric compositions. The article concludes that 80/20 cotton-polyester blend exhibits the best thermal comfort for winter, while 100% cotton is recommended for summer.
In summary, this article comprehensively explores the growth of the knitting sector, the importance of comfort in textiles, and a research project evaluating the thermal comfort properties of different fabric compositions. The inclusion of specific test results and recommendations adds depth to the article's credibility and usefulness for those in the textile industry.
