APhase Change Material (PCM) is a substance with a high heat of fusion, whichmelting and solidifying at certain temperatures, is capable of storing orreleasing large amounts of energy. The only phase change used for PCM is thesolid-liquid change. Initially, the solid liquid PCM perform like conventionalstorage materials; their temperature rises as they absorb solar heat. Unlikeconventional storage materials, however; when PCM reach the temperature atwhich they change phase (their melting point) they absorb large amounts of heatwithout getting hotter. When the ambient temperature in the space around thePCM material drops, the PCM solidifies, releasing its stored latent heat. PCMtherefore absorb and emit heat while maintaining a nearly constant temperature.Within the human comfort range of 20 to 30C, latent thermal storage materialsare very effective. They store 5 to 74 times more heat per unit volume thanconventional storage materials such as water, masonry or rock.

PCMmaterials have high heats of fusion so they can absorb a lot of energy beforemelting or solidifying. A PCM temperature remains constant during the phasechange, which is useful for keeping the subject at a uniform temperature. Avariety of outdoor apparel products with PCM microcapsules, such as sky wear,hunting clothing, boots, gloves and ear warmers are on the market under thetrade names Outlast and Comfort.

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About the Authors:

Shyam Barhanpurkar, Mr. Tanveer Malik, Ayush Paharia &Vineet Singh are associated with Shri Vaishnav Institute of Technology andScience, Indore

Mukesh Singh is associated with Uttar Pradesh Textile TechnologyInstitute, Kanpur

This article wasoriginally published in the Textile Review, May, 2012, published by SaketProjects Ltd., Ahmedabad.