An Explanation and Comparison of Sweating Hot Plate Standards

There are several standards that require the use of a hot plate apparatus for measuring the dry thermal resistance (insulation) and the evaporative resistance of fabrics: ASTM D 1518, ASTM F 1868, and ISO 11092. In addition, several National Fire Protection Association standards for protective clothing (NFPA 1951, 1971, 1977, 1999) specify the use of this method. All of these methods measure the total resistance (i.e., the resistance of the fabric and the resistance of the surface air layer). The resistance of the air layer alone is determined by conducting a “bare plate” test. This air layer resistance is often subtracted from the total resistance to determine the fabric resistance values. Different standards use different terms for these resistances (R_et or R_ef), and they report the resistances in different units (m² · kPa/W or m² · Pa/W). In addition, some methods call for guarded plates, whereas others use smaller plates where the experimenter must compensate for the lack of a guard by adjusting the data for thick specimens. Some methods control the air velocity over the specimen, while others allow any air speed as long as the calibration requirements on standard fabrics are met. This paper discusses the differences in test instruments, conditions, measured parameters, and units so that data from different labs can be compared and understood. In addition, data from an ASTM interlaboratory study is presented so that the repeatability and reproducibility of the different test protocols on a variety of materials can be discussed.

Reference Information:

McCullough, Elizabeth A., Jianhua Huang, and Kim, Chil Soon. “An Explanation and Comparison of Sweating Hot Plate Standards,” ASTM International Journal, Vol. 1, No. 7, July/August, 2004, Online ISSN: 1546-962X, Paper ID JAI12098 (available online at ASTM.org).

This entry was posted on Monday, August 13th, 2007. It is filed under Apparel, Textiles, and Interior Design.