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Tx Thermal Effusivity Touch Tester

Quantify the Warm-Feel / Cool-Touch Sensation of Textiles and Fabrics with ASTM D7984

Textile selection based on perceived warm-feel. Low effusivity means it feels warm.

C-Therm’s touch tester is the only product for quantifying touch performance that fully complies with ASTM D794. The Tx Touch Tester is employed by the top global sports apparel brands and textile testing labs including: adidas, Columbia Sportswear, Marks (Canadian Tire), Intertek, the Taiwan Textile Research Institute, and Bureau Veritas.

Touch is a critical performance attribute in material selection and quality control for bedding textiles, automotive, and fabrics apparel sectors. Thermal effusivity quantifies how materials feel to the touch, whether warm or cool, taking away the guesswork for industries that want to improve product performance.

This testing was traditionally performed using panels of people, who could subjectively verify whether one material felt warmer or cooler than another, as the thermoreceptors in the human hand can detect the difference between materials. However, such human touch testing is extremely subjective to people doing the touch testing, and having an instrument that can accurately measure thermal effusivity takes away this variability for testing a wide range of materials for different use cases and applications.

Materials with a low thermal effusivity feel warmer and materials with a higher thermal effusivity feel cooler. Testing materials for their thermal performance and touch properties has a broad range of applications, including activewear, diapers, denim, and personal protective clothing, to name a few.

Thermal effusivity testing for textiles has been standardized by the American Society for Testing Materials (ASTM). The industry led standard, ASTM D7984, utilizes C-Therm’s patented Modified Transient Plane Source (MTPS) technology for measurement. C-Therm’s MTPS sensor, employed by the TX Effusivity Touch Tester, is the only standardized instrument for characterizing the thermal touch properties of textiles and other materials.

How Consumer Brands Use “Cool-Touch” and “Warm-Feel”

What thermal effusivity measurement is required to support claims that a material can warm you up or cool you down?

Major brands are currently employing a threshold of between > 200 – 280 Ws1/2/m2K as the cut-off for classifying “cool-touch” materials. Conversely, a range of < 65 – 100 Ws1/2/m2K has been set to classify materials that rank in the “warm-feel” category.

THE WARM FEEL – COOL TOUCH PRODUCT PERFORMANCE INDEX

Tx Effusivity Touch Tester: Simplify Thermal Effusivity Testing with the Modified Transient Plane Source (MTPS) Technique

Measure the thermal effusivity of textiles with the Tx Effusivity Touch Tester by C-Therm, creators of industry-leading thermal conductivity equipment who helped develop the ASTM D7984 standard. The Tx Effusivity Touch Tester is the only instrument that conforms to the standard.

This thermal effusivity instrument is equipped with the patented Modified Transient Plane Source (MTPS) sensor, a single-sided sensor that measures the thermal effusivity of a broad range of textiles and fabrics in 1 to 3 seconds. Industry leaders rely on the MTPS sensor to test product performance including Mark’s, Under Armour, adidas, Columbia, Tempur Sealy, and 3M.

To learn more about the Tx Effusivity Touch Tester, request pricing from C-Therm and we will provide more information for measuring thermal effusivity for your application needs.

Request Custom Pricing

The Tx Effusivity Touch Tester, paired with the compression test accessory

Tx Effusivity Touch Tester Product Specifications

Compression Test Accessory with single layer Air Hoop

Thermal Effusively Range 5 to 1,600 Ws½/m²K
Additional Measurements Thermal conductivity
Specific heat capacity (derived)
Temperature Range -50º to 200ºC
Moisture Range 0% – 90% Relative Humidity (non-condensing)
Precision Better than 1%
Accuracy Better than 5%
Test Time 0.8 to 3 seconds
Sensor Size 18mm diameter
Minimum Sample Size Min. diameter of 18 mm
Min. thickness is dependent
on the thermal effusively.
Maximum Sample Size Unlimited
International Standard ASTM D7984
Test Method Modified Transient Plane Source (MTPS)
  • Bureau Veritas Guangzhou

    We offer ASTM D7984 testing with the TCi in our lab. We were impressed with the service and support provided by C-Therm."

    Martin Ho,
    Manager - Softline Testing

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  • adidas

    The device is working perfectly."

    Dr. Christian Heyde,
    Sport Science Manager

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Book a Tx Effusivity Touch Test Demo

Measuring touch properties is important for the textile industry where thermal effusivity measurements factor into marketing claim validation, R&D, and quality control. When you schedule a virtual demonstration with C-Therm, we will guide you through using the Tx Effusivity Touch Tester for your application.

BOOK A VIRTUAL DEMO

Methods for Measuring Thermal Effusivity: The Q-Max Method vs The MTPS Method

Before thermal effusivity instruments were developed, researchers relied on The Q-Max method to test the warm- or cool-touch of fabrics and other materials. The Q-Max value does not measure thermal effusivity directly—it uses heat flux to get an approximate measurement of thermal effusivity.

Repeatability and accuracy are common issues with this method as results can vary between instruments and laboratories. Additionally, manual placement of the hot sensor onto the material is a common issue as it can be difficult to establish consistent contact during the measurement process. Despite these issues, the Q-Max method provides a broad range of environmental operating conditions (humidity, pressure) that can closely mimic real-world applications.

The MTPS method measures thermal effusivity directly using a single-sided sensor. A sample is placed onto the sensor and a heat pulse is applied only after consistent contact is established, which leads to better repeatability of results.

Recent research conducted by C-Therm and the Shanghai Entry-Exit Inspection and Quarantine Bureau demonstrated a correlation between measuring materials using the Q-Max value and measuring thermal effusivity directly with the MTPS method. Comparing 16 samples, researchers found similar results between the two methods.

The advantages of using the MTPS method to measure thermal effusivity include:

  • Direct measurement of thermal effusivity – Provides a calibrated measurement of thermal effusivity from a single instrument versus Q-Max, which requires using multiple calculations to get an approximate measurement of thermal effusivity.
  • Fewer constraints on sample preparation – You do not need to spend long periods of time preparing the sample. You simply place the sample onto the sensor.
  • Shorter test times – Whereas the Q-Max method requires approximating thermal effusivity from a series of calculations, the MTPS Method is largely hands-off: Once you place the sample on the sensor, thermal effusivity is calculated in 1 to 3 seconds.
  • Simple, precise, and reproducible results – A uniform amount of heat is applied to the sample via the MTPS sensor’s guard ring technology to ensure accuracy that you can reproduce across your samples.

The Tx Effusivity Touch Tester has become the global standard for measuring the “warm-feel” or “cool-touch” of textiles and other materials. Powered by C-Therm’s patented Modified Transient Plane Source (MTPS) sensor, it is the only instrument that is recognized by ASTM International for measuring thermal effusivity.

How the Tx Effusivity Touch Tester Works

The Tx Effusivity Touch Tester employs the Modified Transient Plane Source (MTPS) technique. The one-sided, interfacial heat reflectance sensor applies a momentary constant heat source to the sample. Thermal effusivity is measured directly, providing a detailed overview of the thermal characteristics of the sample.

  • Modified Transient Plane Source (MTPS)

    Modified Transient Plane Source (MTPS)

    Simple and Precise. The MTPS method employs a single-sided sensor to directly measure thermal conductivity and effusivity of materials. The MTPS method has the highest precision, highest sensitivity, shortest test time, and is the easiest to use among all three techniques.

    Principles of Operation

    Principles of Operation

    Trident’s primary sensor employs the Modified Transient Plane Source (MTPS) technique in characterizing the thermal conductivity and effusivity of materials. It employs a single-sided, interfacial heat reflectance sensor that applies a momentary constant heat source to the sample. Typically, the measurement pulse is between 1 to 3 seconds. Thermal conductivity and effusivity are measured directly, providing a detailed overview of the heat transfer properties of the sample material.

    How It Works

    1. A known current is applied to the sensor's spiral heating element, providing a small amount of heat.
    2. A guard ring surrounds the sensor coil to support a one-dimensional heat transfer into the sample. The applied current results in a rise in temperature at the interface between the sensor and the sample, which induces a change in the voltage drop of the sensor element.
    3. The rate of increase in the sensor voltage is used to determine the thermal properties of the sample. The voltage is factory-calibrated to temperature. The thermal conductivity is inversely proportional to the rate of increase in the temperature at the point of contact between the sensor and the sample. The voltage is used as a proxy for temperature and will rise more steeply when lower thermal conductivity materials (e.g. foam) are tested. Conversely, the voltage slope will be flatter for higher thermal conductivity materials (e.g. metal). With the C-Therm Tx Effusivity Touch Tester, tabular thermal conductivity results are reported in real-time making thermal conductivity measurement fast and easy. No regression analysis is required.
  • Unifi Manufacturing Inc.

    For any group interested in measuring the thermal effusivity of materials, I would absolutely recommend C-Therm to them. The machine can be set up to analyze many different types of materials, which makes it a very versatile tool."

    Katherine Barrows,
    GIT Prototype & Technology Manager

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Watch the Webinar: Using the MTPS Method to Quantify Temperature Regulation (Q-Max Correlation)

Quantifying the warm-feel and cool-touch of fabrics plays a significant role in temperature regulation for performance textiles. Watch the webinar to learn about methods for measuring heat flux, including a comparison of the MTPS and Q-Max methods.

WATCH THE WEBINAR NOW

What are the Units of Thermal Effusivity?

Thermal effusivity calculates what it feels like when your hand comes into contact with a material; the sensation of warmth or coolness as you encounter an object at ambient room temperature.

Thermal effusivity units are Ws1/2/m2K and is a measurement of the square root of three values:

  • Thermal conductivity (W/mK, or watts per meter-kelvin)
  • Density (kg/m3, or kilogram per cubic metre)
  • Heat capacity (J/kgK or Joule Per Kilogram Per Kelvin)

To learn more about the correlation of effusivity and touch perception and calculating warm-feel/cool-touch thermal properties, watch C-Therm’s webinar on quantifying thermal touch performance.

Watch the Webinar

Applications for Thermal Effusivity in the Textiles Industry

C-Therm’s TX Effusivity Touch Tester allows researchers to quantify the thermal touch properties of textiles in order to find the materials best suited to an application, support performance claims, conduct quality control, and more.

To learn more about thermal effusivity, including how people feel it, how thermal effusivity is quantified using instruments, and how it factors into product, marketing, and research and development decisions, watch the video below.

Textile selection with different thermal effusitivy.

Video transcript: Touch. It’s one of our critical senses in perceiving the world—everything from the clothes we wear to the bedding we sleep in. The thermoreceptors in our skin monitor and relay information to our brains about everything we come in contact with. This helps us make decisions about what feels pleasant to the touch and keeps us safe. Human skin is very good at detecting differences in a material’s ability to transfer heat, such as the warmth of a fleece sweater compared to the coolness of leather.

This material property is known as thermal effusivity—as a metric, it can be used to quantify a textile’s ability to exchange thermal energy between skin and fabric. Why is this important? Because human test panels have established a positive correlation between our touch perception of the warmth or coolness of a textile, and its thermal effusivity. In other words, our perception that certain materials will keep us warm or help us cool down is quantifiable. We know this is important in quantifying performance in a wide range of applications—including diapers, activewear, personal protective clothing, upholstery, neoprene dive suits, and bedding. Our skin’s thermoreceptors are giving us good information, though subjective.

The C-Therm Tx Effusivity Touch Tester quantifies warm and cool feel for you, making what was previously subjective into a metric that can be quantitatively measured. It provides accurate measurements across a range of real world scenarios, including higher humidity environments and under varying compressive loads. The C-Therm Tx Effusivity Touch Tester measures the science of touch—so you can provide the comfort.

C-Therm Thermal Effusivity Instruments Are Trusted Globally By Leading Textile Testing Facilities

In 2016, C-Therm worked with industry to form a new ASTM standard for characterizing the touch properties of textiles and fabrics based on C-Therm’s MTPS technique. Today, various brand companies and testing labs around the globe have adopted C-Therm’s Tx Effusivity Touch Tester into their R&D and quality control processes.

Below is a quick guide to laboratories worldwide that offer ASTM D7984 testing:

Case Studies for Thermal Effusivity Measurement

C-Therm adapted the MTPS sensor to characterize the thermal properties of a range of textiles and fabrics. Learn more about the different applications of thermal effusivity below.

Characterizing The “Warm-Feel” Of Activewear Textiles

Manufacturers of high-performance apparel use thermal effusivity measurements to evaluate whether a material is able to keep you cool during high-energy activities, or keep you warm in colder environments. A fabric with a higher thermal effusivity feels cool, while a fabric with lower thermal effusivity feels warm. Using C-Therm’s MTPS sensor, a major Canadian retailer is able to measure the “warm-feel” of textiles in order to create thermal underwear and activewear. The table below highlights results from four candidate materials in terms of their thermal effusivity.

Characterizing The “Cool-Touch” Of Bedding Textiles

Producers of bedding textiles aim for materials with a high thermal effusivity because they can promote that their products have a “cool-touch.” Using the TX Effusivity Touch Tester, a mattress supplier tests three different coatings to determine which one has a higher thermal effusivity. The chart below highlights results from the study.

Measuring Thermal Effusivity Under Wetted Conditions

An outdoor retailer was interested in assessing how the feelings of “warmth” changed with increased moisture content. Water has a very high thermal effusivity (~1600 Ws½/m²K) compared with that of dry textiles (100 – 200 Ws½/m²K). Notice the thermal effusivity of the cotton textile is twice the effusivity of the micro-fibre material when moderately wet with 10 sprays of water. Incidentally, when fully saturated, both materials have an effusivity very close to that of water itself. This reinforces that if you fall in a cold lake, the best thing you can do to improve your comfort is to remove your clothing upon exiting. However, technical apparels such as this micro-fibre material can provide substantial improvements in comfort under moderate wetting conditions.

Testing the Performance and Comfort of Diapers

Nothing feels better on a baby’s skin than a dry, warm diaper! Diapers are made of 3 key layers: the topsheet, the surge layer, and the absorbent core. When wetted, the diaper’s surge layer disperses the liquid throughout the absorbent core, reducing the wetness from the topsheet and the overall coldness of the diaper. Thermal effusivity can quantify the diaper’s ability to exchange thermal energy between the diaper and the baby’s skin. In characterizing the thermal effusivity of the diaper under dry and wetted conditions, the performance of the diaper can be quantified as to a critical performance attribute for the product based on touch or feel. High effusivity values represent a “cool-feel” and low effusivity values indicate a “warm-feel” to the material. Water has an effusivity value of ~ 1600 W s1/2 m-2 K-1, compared to a dry diaper in the range of 50-100 W s1/2 m-2 K-1.

Test Results

Comfort and warmth are associated with a low thermal effusivity. Therefore, diaper companies strive to achieve the lowest possible thermal effusivity value when their diapers are dry and wetted. As seen in the chart below, the thermal effusivity increases dramatically after the diaper is wetted. However, the leading brand diaper can maintain a more comfortable feel for the baby after the diaper is wetted.

Thermal Effusivity of no name brand diapers vs leading brand diapers

Measuring Material Quality Under Compaction

When testing some fabrics, it may be necessary to measure thermal effusivity as the material is being compressed. This can be accomplished using C-Therm’s Compression Test Accessory. There is no standard level of compression available, as the level of compression is dependent on the application. Compression force is intended to measure performance under “real-world” conditions. For example, the level of compression you would use to test the insulation quality of a down jacket would be minimal compared to measuring a down sleeping bag.

Ready to Get Started with Thermal Effusivity Measurement? Get Pricing

Organizations seeking thermal effusivity measurements need to determine how to adapt instruments for their application. When you request pricing from C-Therm, you’ll also receive a customized recommendation for how to measure thermal properties for your application and industry.

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SIMPLIFYING THERMAL CONDUCTIVITY

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