The main raw material of air conditioning filter cloth is polyester. The basic component of polyester is polyethylene terephthalate, so it is also called polyester fiber ( PET ). From the perspective of polyester molecular composition, it is composed of short aliphatic hydrocarbon chains, ester groups, benzene rings, and alcohol - terminated hydroxyl groups. In addition to the presence of two alcohol - terminated hydroxyl groups in the polyester molecule, there are no other polar groups, so the hydrophilicity of the polyester fiber is extremely poor. Polyester molecules contain about 46% ester groups. The ester groups can undergo hydrolysis and thermal cracking at high temperatures, and will be saponified in contact with alkalis, reducing the degree of polymerization. Polyester molecules also contain aliphatic hydrocarbon chains, which can make the polyester molecules have a certain Flexibility, but because there are benzene rings in the polyester molecules that cannot be rotated internally, the polyester macromolecules are basically rigid molecules, and the molecular chain is easy to maintain linearity. Therefore, polyester macromolecules are easy to form crystals under this condition, so the crystallinity and orientation of polyester are relatively high. The air filter material is to electrostatically charge the polypropylene fiber during the melt - blown manufacturing process to make it into an electrostatic electret melt - blown non woven fabric ( filter paper ) with a fiber diameter of 2 - 5 μm. This kind of air filter media not only uses the filtering mechanism of traditional air filter materials, but also uses the coulomb force of charged fibers to capture particles, so the efficiency increases and the resistance decreases. This filter material is currently used in 3M surgical masks ( N95, N97, N99 ) that have the function of preventing viruses ( including SARS virus ) in the world. Filter cloth can be divided into polyester, polypropylene, nylon, vinylon, cotton, new high - efficiency materials and other filter cloths according to the nature of the material. There are two types according to the way of weaving. One is weaving cloth, including polyester, polypropylene, nylon, vinylon, cotton, etc. There are several weaving methods for filter cloth patterns, plain weave, twill weave, satin weave, double weave and so on. The other is non woven, including non woven fabrics, geotextile fabrics, filter felt fabrics , etc. Methods include spunbond, needle punch, water weaving, etc. The silk material of filter cloth is also divided into three types: monofilament, long-fiber multifilament, and short fiber cloth. ( Among them, the polyester staple fiber series is also divided into large chemical fibers and small chemical fibers). Meltblown filter material and hvac filter media are also important in our daily life.