A polypropylene tarp Poly Tarp is not a traditional fabric, but rather, a laminate of woven and sheet material. The center is loosely woven from strips of polypropylene plastic, with sheets of the same material bonded to the surface. This creates a fabric-like material that resists stretching well in all directions and is waterproof. When treated against ultraviolet light, these tarpaulins can last for years exposed to the elements, but non-UV treated material will quickly become brittle and lose strength and water resistance if exposed to sunlight. Most import Poly tarps are non-UV treated.