Thermal Performance Testing of Masks: Using effusivity to understand cool-touch / warm feel.
Featuring premium masks from Balas Textile and test data from C-Therm Tx Effusivity Tester
Masks have become a critical piece of a person’s sporting wear, everyday wardrobe, safety and comfort level. Covering both mouth and nose, with contact directly upon a person’s face, the thermal performance of a mask is a critical attribute.
By testing the inside of high performance masks from Balas Textile with a C-Therm MTPS sensor (ASTM D7984) the effusivity and effective heat transfer rate was evaluated and compared. For technical textiles such as those used in Balas Masks, accuracy and test setup are important to ensure data is representative of a user’s touch perception.
3 commercially available, masks from Balas Textiles, all made of technical textiles were chosen for comparison: “Cocoon”, “Breeze” and “Bloom”. The C-Therm Tx Touch Tester was utilized with a Compression Test Accessory to control stretch and contact, and an Air Hoop sample holder to allow for single layer testing with an air backing.
|Cocoon||Thermal Effusivity & Conductivity||C-Therm MTPS||Air Hoop, 100gf via CTA||Ambient||
10 tests of each sample
Monitor and report temp. & humidity
|Bloom||Thermal Effusivity & Conductivity||C-Therm MTPS||Air Hoop, 100gf via CTA||Ambient|
|Breeze||Thermal Effusivity & Conductivity||C-Therm MTPS||Air Hoop, 100gf via CTA||Ambient|
Modified Transient Plane Source Sensor + Accessories
The single-sided, patented Modified Transient Plane Source sensor allows for precise, accurate and repeatable testing of fabrics and textiles in accordance to ASTM D7984, reporting on Thermal Effusivity (Ws1/2/m2K) and Thermal Conductivity.(W/mK). With a 1 second heat pulse resulting in approximately 1 degree Celsius change in temperature at the sensor surface, the rate of temperature change over time is analyzed to determine thermal properties of a material.
By employing an Air Hoop a single layer of the material is tested to represent the mask being worn on a person’s face. The resulting effective thermal effusivity is representative of the warm-feel (low effusivity) or cool-touch (higher effusivity) of the mask against human skin. The effective thermal conductivity represents the material’s ability to transfer heat away from the body.
|Sample ID||Temperature||Humidity||Compression||Thermal Effusivity (Ws1/2/m2K)||Effusivity %RSD||Thermal Conductivity (W/mK)||Conductivity %RSD|
The “Cocoon” mask, designed for winter wear with a fleece-like material, tested at the lowest thermal effusivity, meaning it will feel warmest of the 3 masks against the face. Both “Breeze” and “Bloom” tested significantly higher, at over twice the effusivity units. Touch perception will typically recognize a delta over +10 or more effusivity unit when under 100 Ws1/2/m2K , meaning all three of these samples will feel different (with Bloom feeling the coolest).
It’s important to consider that these parameters are a “piece of the puzzle” that make up the complex thermal profile of a fabric. So while Bloom may feel coolest, Breeze may have better wicking effect (outside the scope of this testing) which can change effective thermal comfort. Wet to dry testing experiments would be a logical next step for further analysis of the masks.
About the Author
|Written by Jarett Nickerson, VP – Sales & Marketing at C-Therm, in collaboration and with permissions from Balas Textile.|