Anyone who’s ever worked in a dairy freezer knows it doesn’t take much time to become uncomfortable to the point of having to bail on the work. There goes a lot of production—and money.
That’s just one example presented by Barbara Pause, CEO of Textile Testing and Innovation, Longmont, Colo., at IFAI Advanced Textiles Expo in Minneapolis in October. In her presentation, “New Approaches for Enhancing the Thermal Performance and the Moisture Management of Protective Garments,” she also talked about the other end of the thermal spectrum and the challenges of dealing with extreme heat.
Textile Testing specializes in using phase-change materials (PCM) and shape-memory materials (SMM) technology in the development of textiles and polymers to accommodate comfort and thermal protection in work apparel, building materials and automotive interior components.
The difference between the technologies is that PCMs regulate heat transfer through a garment system while SMMs regulate moisture transfer. Both technologies together provide active thermal and moisture management, which adapts the heat and moisture transfer through the garment to the prevailing wearing conditions. The two effects are triggered by temperature.
PCMs possess the ability to change physical state from solid to liquid and back within a certain temperature range. During this transformation, the materials absorb, store and release large amounts of “latent heat” with a change in the material’s temperature; this makes PCMs ideal for heat storage. At certain temperatures in the heating process, SMMs revert to a shape previously impressed on it during the production process; they also possess a “superelastic“ behavior at temperatures above the PCM transition temperature.
Pause noted that in the food industry, work-condition temperatures can fluctuate between 23 degrees F and -22 F in cold-storage units. An hour is the usual time limit working under such conditions before workers have to re-establish a comfortable level of warmth. “Longer work times would equal more productivity,” she noted.
Moisture-management is critical to worker comfort, but conventional cold-work apparel keeps moisture (sweat) inside next to the body, which can add to the worker’s discomfort.
At the other end of the spectrum, handling extremely hot materials and/or working in hot conditions also limits worker comfort and productivity. Heat-protective gloves and body suits utilize the PCM technology.
SMM technology comes into play in particular for athletes and others who work outside in less-than-ideal—i.e., rainy—conditions. As body heat rises, the “pores” in the SMM fabric open, allowing moisture to wick away from the body while the outside layer prevents the rain from “coming in.”
A combination of SMM and PCM is used in cold-protective garments, keeping the cold out, while the worker’s body generates heat and sweat that must be wicked away.
These “smart materials” that react to prevailing conditions are also less bulky, Pause noted.