Thermal Resistance of Air-Filled Mattresses: Measurement Repeatability and the Effect of Selected Test Parameters

There is no standardized test method specifically for determining the thermal resistance (R-value) of air-filled mattresses. Unacceptable inter- and intra-laboratory variations in round-robin testing have been attributed to differences in the test apparatus and test parameters used. To identify relevant sources of variation, the repeatability of the guarded hotplate apparatus (in a double plate configuration) was first characterized, and then the effect of modifying selected test parameters on mattress thickness and thermal resistance was investigated. Two mattress types, in two different sizes, were examined: one contained air only while the other contained air plus a nonwoven polyester fill. It was found that repeatable outcomes could be attained when using the guarded hotplate apparatus (95 % repeatability limit of less than 0.08 m²K/W for all mattresses tested). The modification of test parameters had significant effects on mattress thickness or R-value, or both. External pressure, the temperature difference across the specimen, supplementary insulation, mattress size, and environmental conditions affected both the thickness and R-value of the test mattresses. Inflation pressure, over the range tested, did not have a significant effect on the R-value but did influence mattress thickness. This work highlights the need for the standardization of the test apparatus and test parameters and will aid in the development of a standardized test method.