Why does the fabric feel cool

Why does the fabric feel cool
Do you know the testing standards for cooling performance

 

 

The coolness of fabrics is mainly related to the fiber thermal conductivity, specific heat capacity, and fabric structure

 

thermal conductivity
specific heat capacity
Fiber and fabric structure
What are the standards for testing cooling performance

 

 

thermal conductivity

 

The higher the thermal conductivity, the stronger the cooling sensation of the fabric in contact. Among commonly used fibers, nylon and polyester have high thermal conductivity and are mostly used for summer clothing; Natural fibers such as wool and cotton have low thermal conductivity and are often used for winter clothing insulation. It is difficult to achieve sufficient cooling sensation solely based on fibers themselves. Currently, the main research and development direction is to add high thermal conductivity substances such as nano mica and shells during chemical fiber spinning to make fibers with longer cooling sensation and washability. For example, Kusima Nano Cooling Fiber can produce an instant cooling sensation of 1-2 ℃ when in contact with the skin, with a temperature difference of 5-6 ℃ under sunlight exposure; Some companies also process cooling powder into PET and PA cooling masterbatch, add them to fibers and weave them, and match them with irregular cross-section fibers for better cooling effect.

 

 

specific heat capacity

 

The larger the specific heat capacity, the more heat the fabric absorbs instantly, the slower the heating, and the more pronounced the cooling sensation; Nylon has both high thermal conductivity and high specific heat capacity, making it commonly used in products such as sun protection clothing and summer quilts; The increase in thermal conductivity of natural fibers is limited, and the specific heat capacity can be enhanced by post-treatment processes using cooling agents such as peppermint oil and xylitol. However, this cooling sensation will weaken with increasing washing times.

 

 

Fiber and fabric structure

 

Reducing the air content in the gaps between fibers and yarns (opposite to the design of warm fabrics) can enhance the coolness. By designing fibers with irregular cross-sections and using three-dimensional weaving methods, it is possible to accelerate sweat release, improve air flow, and enhance coolness.

 

 

What are the standards for testing cooling performance
GB/T 35263-2017 "Detection and Evaluation of Instantaneous Cooling Sensitivity of Textiles": This is the first standard in China regarding the cooling sensation of textiles, and this method is applicable to all fabrics and their products.
The testing principle is to place a thermal detection plate with a temperature higher than the sample in contact with the sample under specified test environmental conditions, measure the temperature change of the thermal detection plate over time, and calculate its contact cooling coefficient (qmax), which can characterize the cooling performance of the sample at the moment of contact. The larger the qmax value, the stronger the cooling sensation felt by the skin, while the smaller the value, the weaker the cooling sensation felt by the skin.
In this standard, when Δ T=15 ℃, the contact cooling coefficient qmax is ≥ 0.15, indicating that the sample has good contact cooling properties. FZ/T 73067-2020 "Contact Cooling Knitted Clothing": This standard is aimed at contact cooling knitted clothing and divides the cooling feeling into three levels: excellent products, first-class products, and qualified products. The contact cooling coefficient is required to be no less than 0.25, 0.20, and 0.18, respectively.
FZ/T 62042-2020 "Cool Fabric Bedding": This standard is for bedding products, dividing them into three levels: A, AA, and AAA. The required contact cooling coefficients are not less than 0.20, 0.25, and 0.30, respectively, indicating that the cooling requirements for bedding products are even higher than those for clothing.