Thinsulate

Thinsulate is a synthetic fibre used for thermal insulation in clothing. The word is a portmanteau of thin and insulate, and is a trademark of the 3M Corporation. The material was first sold in about 1980.

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Thinsulate fibres are about 15 microns in diameter, which is thinner than the polyester fibres normally used in insulation for clothing such as gloves or winter jackets. Advertising material for thinsulate [[1]] suggests that thinsulate is more effective due to the increased density of fibers with decreased size of fibers compared with more traditional insulation. Like most insulation materials, the gaps between fibers not only reduce heat flow, but also allow moisture to escape. The insulation properties are benficial for retaining some of the heat produced by the body for comfortable warmth while the moisture produced, e.g. by sweating, is supposed to evaporate.

The manufacturer claims that, for a given thickness of material, Thinsulate provides 1 to 1.5 times the insulation of duck down, while being much less water-absorbent and much more resistant to crushing. Based on an insulating value for down of 4.8 Clo per 1.1 inch [2], that would mean Thinsulate provides about 6.5 Clo per inch (i.e., an imperial R-value of 5.75 per inch.

In 1978 Thinsulate insulation was introduced, marketed as providing "warmth without bulk". Marketing material suggests it retains its insulating ability even in damp conditions.

Materials Safety Data Sheets from the manufacturer show that different varieties of Thinsulate are made from different mixtures of polymers, but most are primarily Polyethylene terephthalate or a mixture of Polyethylene terephthalate and polypropylene. Other ingredients in some include polyethylene terephthalate–Polyethylene isophthalate copolymer and acrylic.