Introduction
As a highly valued textile material in the modern era, wool fabrics require careful consideration of their air permeability. Clothing materials must possess a certain degree of breathability since human skin continuously undergoes respiration, exchanging gases with the environment while shedding skin flakes and excreting sweat and oils. From a hygiene perspective, breathable fabrics facilitate gas exchange between the fabric’s interior and exterior, promoting skin metabolism. Wool and fine woolen fabrics are popular for their variety, unique styles, and excellent wearability.
For winter garments, lower air permeability helps retain warmth, whereas summer fabrics benefit from greater breathability to dissipate body heat, ensuring a cool and comfortable feel while maintaining adequate insulation. Currently, the development of well-ventilated wool fabrics has become a key research focus in the textile industry of many developed nations. High-quality breathable wool fabrics hold great market potential both domestically and internationally.
Fabric Specification Analysis
Fabric structure significantly impacts fabric properties. Even when using the same raw materials, variations in structural design can lead to considerable differences in fabric performance.
Here, you will find Tables 1 – 1 showing fabric density, yarn thickness, tightness, surface density, volume, thickness, etc., for various fabric samples.
Table 1 – 1 Test Results of Fabric Specification Parameters
| Serial Number | Raw Material | Fabric Weave | Fabric Density (/10cm) | Yarn Linear Density (tex) | Tightness (%) | Thickness (mm) | Fabric Surface Density (g/m²) | Volume (g/m³) | ||||
| Warp Density | Weft Density | warp yarn | weft yarn | Warp – wise Tightness | Weft – wise Tightness | Total Tightness | ||||||
| 1# | Wool | Warp – rib | 384 | 376 | 17 |
11 |
65.3 |
48.9 |
82.3 |
0.256 |
190.8 |
745.30 |
| 2# | Wool/Polyester | Plain weave | 230 | 240 | 27 | 29 | 57.5 | 62.4 | 84.0 | 0.338 | 212.00 | 627.20 |
| 3# | Polyester/Visco | Plain weave | 212 | 238 | 33 | 25 | 46.6 | 45.2 | 70.7 | 0.355 | 188.80 | 531.80 |
| 4# | Wool/Acrylic | 3/1 Left – twill | 418 | 184 | 27 | 42 | 87.8 | 48.7 | 93.7 | 0.436 | 243.20 | 557.80 |
| 5# | Wool | 2/1 Right – twill | 334 | 278 | 27 | 28 | 70.1 | 58.4 | 87.6 | 0.280 | 176.40 | 630.00 |
| 6# | Wool | Plain weave | 490 | 330 | 15 | 12 | 78.4 | 45.4 | 88.2 | 0.438 | 289.60 | 661.20 |
| 7# | Viscose/Wool | Plain weave | 240 | 240 | 30 | 30 | 60.0 | 60.0 | 84.0 | 0.404 | 296.40 | 733.70 |
| 8# | Acrylic | Warp – faced satin | 446 | 242 | 24 | 24 | 98.3 | 53.2 | 99.2 | 0.654 | 382.80 | 585.30 |
| 9# | Viscose/Wool | 2/2 Left – twill | 394 | 420 | 15 | 10 | 75.5 | 46.3 | 86.8 | 0.312 | 243.60 | 780.80 |
| 10# | Viscose/Wool | 3/3 Left – twill | 482 | 394 | 15 | 15 | 57.3 | 67.2 | 86.0 | 0.374 | 285.20 | 762.60 |
| 11# | Polyester | 2/2 Right – twill | 472 | 356 | 12 | 10 | 67.5 | 46.5 | 82.6 | 0.356 | 284.80 | 800.00 |
| 12# | Acrylic | Warp – faced twill | 364 | 236 | 12 | 10 | 51.0 | 30.7 | 66.0 | 0.288 | 191.20 | 663.90 |
| 13# | Viscose/Wool | 3/2 Left – twill | 234 | 372 | 15 | 12 | 65.1 | 55.8 | 84.6 | 0.390 | 284.60 | 729.80 |
| 14# | Polyester/Wool | Plain weave | 308 | 308 | 13 | 12 | 43.1 | 43.1 | 67.6 | 0.220 | 307.60 | 139.80 |
| 15# | Polyester/Acrylic | Combined weave | 482 | 386 | 13 | 9 | 72.3 | 46.3 | 85.1 | 0.334 | 220.00 | 658.70 |
| 16# | Polyester | Warp – based weave | 422 | 400 | 10 | 10 | 50.6 | 48.0 | 74.3 | 0.260 | 187.60 | 721.50 |
Air Permeability Testing Procedures
Testing Materials
Selected samples must be flat and wrinkle-free, with no visible defects. The edges of the samples must be aligned parallel to either the warp or weft yarns.
Testing Instruments
The Air Permeability Tester for Fabric is used to measure fabric breathability. Air permeability is quantified by the volume of air passing through a unit area of fabric under a specified pressure differential. The higher the airflow, the better the breathability.
Testing Conditions
The testing environment is maintained at a temperature of 20°C ±3°C and relative humidity of 65% ±3%. Samples are pre-conditioned under these conditions for 24 hours before testing. Standard atmospheric conditions for pre-conditioning, conditioning, and testing are based on GB6529.
Testing Principle
Using the principle of fluid continuity and Bernoulli’s theorem while considering gas viscosity and compressibility, the airflow equation is derived. Air permeability is expressed in terms of airflow volume through the fabric per unit area under steady-state conditions and a constant pressure differential.
The Air Permeability method is commonly used in textile testing to ensure accurate fabric performance evaluation. This method measures the ease with which air can pass through a fabric, helping manufacturers determine the suitability of materials for various applications. By utilizing advanced air permeability testers, textile professionals can obtain precise and reliable data to optimize fabric functionality.
Results and Analysis
Relationship Between Airflow and Air Permeability Rate
Figure 3-1 demonstrates a linear relationship between airflow and permeability rate: as permeability increases, airflow increases. The following regression equation is derived:
Y = -1.015 + 0.673 * X
Relationship Between Fabric Mass and Air Permeability
Figure 3-2 shows no clear correlation between fabric mass per unit area and air permeability. Sample #2 has the highest fabric permeability, while #10 has the lowest. Some samples (e.g., #9, #10, #13, #6, #8) exhibit a decline in air permeability as fabric mass increases, while others (#2, #5) show increased permeability with higher mass.
Relationship Between Fabric Volume and Air Permeability
Figure 3-3 reveals that air permeability decreases as fabric volume increases. This occurs because larger fabric volumes reduce the void spaces per unit area, thereby restricting airflow. Notably, samples #10, #2, #8, and #13 show significant deviations, likely due to differences in material composition and thickness.
Impact of Fabric Density on Air Permeability
Fabric density has a substantial effect on air permeability. As fabric density increases, air permeability decreases due to reduced inter-yarn gaps and higher airflow resistance. Once density reaches a critical threshold, further increases primarily compress the yarns rather than significantly altering pore size, resulting in minimal additional reduction in permeability.
Conclusion
Fiber Material
Natural fibers generally offer better breathability than synthetic fibers. Among natural fibers, cotton, linen, and silk provide superior fabric permeability compared to wool, which has slightly lower breathability. The moisture absorption properties of fiber materials also impact air permeability, with higher moisture absorption correlating to lower permeability.
Fiber Cross-Section
Fabrics made from irregularly shaped fibers typically exhibit better air permeability than those composed of round cross-section fibers.
Scientific Analysis of Factors Affecting Fabric Air Permeability
The primary factors influencing fabric breathability include material type, fabric structure, finishing processes, wash cycles, and heat treatments. Below is a scientific breakdown of these key factors:
The Influence of Fabric Material on Air Permeability
Table 2 indicates that cotton, linen, and wool-based natural and protein fibers have better breathability than synthetic fibers such as nylon and polyester.
The Influence of Fabric Structure on Air Permeability
Fabric structure significantly impacts air permeability, ranked as follows: Open-weave fabrics > Satin fabrics > Twill fabrics > Plain-weave fabrics.
This is because the plain fabric warp and weft lines interweave the most times, the pore space between the yarns is small, air permeability is also small; permeable fabric yarn gap is larger, air permeability is also larger. Due to changes in fabric organization and density, caused by the increase in floating length, the fabric permeability also increases. When the fabric warp and weft yarn count unchanged, the warp density or weft density increased, the fabric permeability decreased; fabric density unchanged, while the warp and weft yarn fineness decreased, the fabric permeability increased. Within a certain range, the yarn twist increases, the weight per unit volume of yarn increases, the yarn diameter and fabric tightness decreases, and the fabric air permeability increases.
Plain-weave fabrics have the highest interlacing frequency and smallest pores, reducing breathability.
Open-weave fabrics have larger gaps between yarns, enhancing breathability.
The Influence of Finishing Methods on Air Permeability
Different finishing techniques impact air permeability test results. Liquid ammonia finishing can improve fabric permeability, whereas three-proof finishing reduces it significantly.
The same specification of cotton plain fabric (11.7tex×11.7tex315 roots/10cm×267 roots/10cm) was selected, and the fabrics were subjected to post-finishing such as softness, liquid ammonia softness, no-ironing, liquid ammonia no-ironing, liquid ammonia moisture cross-linking and three-proofing, etc, respectively, so as to compare the effects of different finishing methods on the fabric breathability, and the results are shown in Fig. 2.
As can be seen from Fig. 2, liquid ammonia finishing can improve the air permeability of fabrics, and the air permeability of liquid ammonia tide crosslinked fabrics is the best; the air permeability of ordinary soft and non-iron finishing is relatively poor. Liquid ammonia soft and liquid ammonia non-iron fabric permeability than the corresponding soft and non-iron fabrics to improve 20%.
This is because the cotton fabric by liquid ammonia finishing, fiber thinning, hollow cavity tube and pore space becomes smaller, flat ribbon twisted to reduce the fiber thinning, so that the fabric air permeability rise. Three-proof finishing fabric air permeability is the worst, this is because the three-proof finishing will be waterproof and oil-proof finishing agent coated on the surface of the fabric, and the chemical reaction with the fiber, crosslinked into a film on the surface of the yarn, preventing water and oil from entering the interior of the fibers or fibers between at the same time, but also reduces the amount of air permeability of the fabric.
The Influence of the Number of Washes on Air Permeability
The effect of the number of washes on the air permeability of the fabrics was investigated by using the durable press washing procedure of AATCC 135 method for different specimens, i.e., water temperature (49±3)℃, washing for 10 min, dewatering for 4 min, and tumble drying, and the results are shown in Fig. 3.
As can be seen from Fig. 3, although the number of washings has different effects on the air permeability of different fabrics, it basically follows a similar law: during the first 5 washings, the air permeability of the fabrics changes the most; during the 5-100 washings, the air permeability of the fabrics changes less and tends to be stable; among them, the air permeability of the fabrics has a tendency to increase slightly for more than 30 washings.
The effect of washing times on air permeability is directly related to the shrinkage rate of fabrics. Fabrics in the process, the yarn is stretched many times, resulting in stress concentration. When the fabric in the role of water, internal stress relaxation, fiber, yarn slow elastic deformation of the return, so that the size of the fabric, density and tightness changes, resulting in a reduction in fabric permeability. Generally, the fabric shrinkage in the process of 5 washing is the most obvious change, and then tends to level off, so the air permeability will have a turning point in the 5 washing. With the increase of washing times, the fiber is gradually worn, the organization becomes loose, the gap between the yarns increases, and the air permeability gradually becomes larger.
Fabric permeability fluctuates across multiple washes:
Greatest change within the first 5 washes
Stable breathability from 5 to 100 washes
Slight increase beyond 30 washes
These effects are due to fiber relaxation, leading to minor structural shifts in the fabric.
The Influence of Heat Treatments on Air Permeability
The air permeability of cotton fabrics with different organizational structures was tested before and after baking, and the results are shown in Fig. 4.
As can be seen from Fig. 4, the air permeability of the fabrics after baking increased compared with that before baking, because the additives immersed in the fabrics before baking did not cross-linking, covered in the fibers and yarns, impeding the flow of air; additives and fibers after baking completely reacted, thus increasing the air permeability.
After heat treatment, fabric permeability increases as applied chemicals undergo full reaction, reducing surface blockages and facilitating airflow.
Recommendations for Highly Breathable Fabrics
Clothes made of fabrics with strong breathability can make us feel more comfortable in hot summer, avoid excessive sweating, and reduce unnecessary discomfort. So, which fabrics have better breathability? Let’s find out together.
Cotton Fabric
Cotton fabric is one of the most common fabrics and also has excellent breathability. It is soft and comfortable, allowing the skin to breathe and not making the body feel stuffy. Especially in summer, wearing cotton clothes can make us feel cool and comfortable. Cotton fabric also has very good hygroscopicity and can absorb the body’s sweat, making us feel drier.
Linen Fabric
Linen fabric is a natural cellulose fiber with excellent breathability and hygroscopicity. The fiber structure of linen fabric is loose, allowing air to circulate freely and making it easier for the skin to breathe. Linen fabric also has very good hygroscopicity and can absorb the body’s sweat, making us feel drier. The disadvantage of linen fabric is that it is prone to wrinkling and needs to be ironed frequently.
Hemp Fabric
Hemp fabric is also a natural cellulose fiber that is also very breathable and moisture wicking. It has a loose fiber structure that allows air to circulate freely, allowing the skin to breathe more freely. Hemp fabric is also very good at absorbing moisture, which absorbs sweat from the body and makes us feel drier. The disadvantage of hemp fabric is that it is easily wrinkled and needs to be ironed frequently.
Pearl Fiber Fabric
Pearl yarn is a new – type cellulose fiber with good breathability and hygroscopicity. The fiber structure of pearl yarn is loose, allowing air to circulate freely and making it easier for the skin to breathe. Pearl yarn also has very good hygroscopicity and can absorb the body’s sweat, making us feel drier. Pearl yarn is soft in texture and comfortable to the touch, making it very suitable for summer wear.
Modal Fabric
Modal fabric is a man – made fiber with good breathability and hygroscopicity. The fiber structure of modal fabric is loose, allowing air to circulate freely and making it easier for the skin to breathe. Modal fabric also has very good hygroscopicity and can absorb the body’s sweat, making us feel drier. Modal fabric is soft in texture and comfortable to the touch, making it very suitable for summer wear.
Highly breathable fabrics—such as cotton, linen, hemp, pearl fiber, and modal—are excellent choices for comfortable summer clothing. When selecting garments, consider additional factors such as style, color, and texture to enhance wearability and aesthetics.
Understanding the Air Permeability Test Procedure and utilizing a high-precision Air Permeability Tester are essential for assessing the breathability of wool fabrics. Factors such as material composition, structural design, finishing methods, washing cycles, and heat treatments all play a crucial role in determining the fabric permeability. By optimizing these factors, textile manufacturers can develop high-performance wool fabrics that meet market demands for breathability and comfort.
For more information on smart textile testing instruments and air permeability test methods, or to obtain professional testing solutions, please contact us!
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