CRAFTEVO is proud to introduce polypropylene insulation. Polypropylene fibers, in comparison to other synthetic and natural fibers, are extremely light, yet yield the greatest volume for a given weight. Specific gravity is often used as a reference for the ratio of density; while the specific gravity of water is 1, polypropylene is 0.91, meaning it will float on water. It is 34% lighter than polyester and 20% lighter than nylon.