Air permeable film (also known as microporous film) is a new type of material in the world. This kind of film is distributed with a large number of micropores. It has the characteristics of air permeability and watertight and is widely used in various fields of human life. With the development of The Times, the film production technology continues to improve.

a. Mechanical physics method: the film through a heated rotary drum with the tip of the needle, with mechanical method, prick out a large number of micro holes; The film is passed through the surface of a porous drum, and hot air is ejected in the pore of the drum at high temperature and high speed to obtain the porous membrane.

b. Chemical method: tetrahydronaphthalene, flowing paraffin wax, surfactant and ring has ketone with the right amount of ratio, appropriate viscosity and surface tension, in the state of particles on the surface of the plastic film evenly dispersed adhesion, and then with air/water heating, the surface adhesion of the solvent particles melt, thus getting the microporous film.

c. Electrical method: for the purpose of improving the film's printability, extruding and bonding, using corona discharge treatment principle to promote production. The microporous films with adjustable pore size between 0.2 mm and 1.0mm were obtained by passing through the film at a high voltage of 7,000 to 15,000 volts.

d. Blow molding tape casting: add calcium carbonate（CaCO₃ ）and other inorganic particles in the raw material, using calcium carbonate particles in the process of stretching and is already set the principle of the junction formation of microcellular plastic substrates, and the pore size of the nanoscale, namely in a square centimeter can be distributed in the area of hundreds of millions of pores, so as to realize the permeability of the membrane is impermeable performance.