There are two main types of waterproof breathable film made of polyurethane PU elastic materials: microporous type and hydrophilic type, the PU film products have unparalleled properties as unique adhesion, wettability, flexibility, abrasion resistance, gloss, etc.
1. PU waterproof breathable film with microporous type: The diameter of the pores of the microporous film is small, only 10-50µm, which is between the water vapor with a diameter of 4X10-4 µm and the water droplet with a diameter of 100-300µm. Under the electron microscope, obvious microporous structure of PU film can be observed, whose air permeability is comparable to that of human skin.
2. PU waterproof breathable film with hydrophilic type. The continuous non-porous film and coating material have a uniform and dense structure on the surface and body. The water resistance is determined by the continuity of the material and the large surface tension, and the breathability is determined by the type, proportion and relative molecular mass of the hydrophilic soft segment of the polyurethane. The microphase separation structure provides the possibility for complex molecular diffusion. Water molecules are transported along the dense molecular chain gaps, absorb water from the high-humidity side, and transfer to the low-humidity side through the hydrophilic groups on the polyurethane molecular chains. Its respiration is generally poor relative to the microporous structure. A new type of polyurethane PU film and coating, by adjusting the proportion and relative molecular weight of its hydrophilic soft segment, its water vapor transmission rate can reach the same level as that of microporous materials, thereby controlling the humidity and heat of the microenvironment in contact with the skin balance. In addition, its dense structure can play a role in blocking dust and bacteria.
POLYSAN supply high quality PU waterproof breathable film for medical industry: surgical caps, medical mattresses, ice packs, bandages, plasma bags, etc.