What is Waterproof Fabric
2015-06-15 09:09 | writer: admin
Waterproof fabric is a natural or synthetic fabric that has been coated with a substance to repel water. Common waterproofing substances include polyurethane, polyvinyl chloride, silicone, and wax. The term "waterproof" applies to the fabric only, not the entire garment. Even if a fabric is entirely waterproof, the seams must be sealed or taped and the zippers must have storm flaps, or the garment is merely water-resistant.
In most cases, waterproof fabric is subject to laboratory testing and must conform to industry standards. A waterproof garment will often be labeled with a rating that denotes how much liquid the garment can be subjected to in 24 hours before the wearer gets wet. For example, a rain jacket rated "20K" can withstand 20,000 millimeters of rain before the waterproofing fails. A rating of 20K is considered excellent, and is usually expensive. Ratings of 5K and 10K are more common, especially for non-specialized, inexpensive rain gear.
Woven fabrics with a waterproof coating have millions of tiny pores, about 1/20th the size of a rain drop but much larger than a molecule of water vapor. These pores allow body heat and moisture to escape while keeping liquid water like rain out. This breathability can also be rated, in grams of water vapor per square meter per 24 hours. For example, a breathability rating of 25K means a garment can allow 25,000 grams of water vapor to pass through a square meter of the fabric in a 24-hour period.