This study examined the effects of household fabric softeners on the thermal comfort and flammability of 100% cotton and 100% polyester fabrics after repeated laundering. Two fabric properties related to thermal comfort, water vapor transmission and air permeability, were examined. A 3 X 2 X 3 experimental design (i.e., 18 experimental cells) was developed to conduct the research. Three independent variables were selected: fabric softener treatments (i.e., rinse cycle softener, dryer sheet softener, no softener), fabric types (i.e., 100% cotton, 100% polyester), and number of laundering cycles (i.e., 1, 15, 25 cycles). Three dependent variables were tested: water vapor transmission, air permeability, and flammability. The test fabrics were purchased from Testfabrics, Inc. To examine the influence of the independent variables and their interactions on each dependent variable, two-way or three-way Analysis of Variance (ANOVA) tests were used to analyze the data.

Results in this study showed that both the rinse cycle softener and the dryer sheet softener significantly decreased the water vapor transmission of test specimens to a similar degree. The rinse cycle softener decreased the air permeability of test specimens most and was followed by the dryer sheet softener. The rinse cycle softener increased the flammability of both cotton and polyester fabrics, but the dryer sheet softener had no significant effect on the flammability of both fabric types. Statistical analysis also indicated that the interactions were significant among the independent variables on water vapor transmission, air permeability, and flammability of the test specimens. For example, the rinse cycle softener significantly decreased the water vapor transmission and air permeability of cotton fabric but had no effect on polyester fabric. The dryer sheet softener also decreased the water vapor transmission of cotton fabric but had no effect on polyester fabric, and it had no effect on the air permeability of both cotton and polyester fabrics. In addition, the air permeability of cotton specimens treated with the rinse cycle softener continuously reduced after repeated laundering, but that of polyester fabrics treated with the rinse cycle softener only reduced after 15 laundering cycles and showed no continuous decrease when laundering cycles increased.

When the influence of fabric softener treatments on flammability was examined, the results showed that the more the specimens were laundered with the rinse cycle softener, the greater the flammability of the test specimens. However, the dryer sheet softener did not have a significant effect on the flammability of the test fabrics even after repeated laundering. For the polyester fabric, all specimens treated with the dryer sheet softener or no softener passed the standard of children's sleepwear even after 25 laundering cycles, but those treated with the rinse cycle softener did not pass the standard.

In conclusion, fabric softener treatment had a significant influence on the thermal comfort (i.e., water vapor transmission and air permeability) and flammability of 100% cotton and 100% polyester fabrics after repeated laundering cycles and the effects were significantly different among the three independent variables (i.e., fabric softener treatments, fabric types, and number of laundering cycles). The applications of these results were also discussed.