Breathable film is an environmentally friendly functional material that is breathable (vapor) and water resistant (liquid, bacteria, dust). The emergence of microporous breathable membranes has a history of over 20 years and has developed rapidly in the past 10 years. China is in the early stages of technology, market, and application. Polyolefin breathable film is made by adding inert fillers to PE or PP carriers, and then preparing and stretching the film. For personal hygiene and care products, breathable film is an upgraded product of ordinary waterproof film. Breathable film and ordinary film cannot be simply replaced, and the reasonable structural design of the product is crucial for reflecting the breathable effect of the breathable film!

Based on my professional experience, this article discusses the performance setting, manufacturing technology, control methods, application fields, development trends, and other issues related to breathable films that are of concern to those in the industry. We hope to be helpful for the production and use of breathable films.

Breathable film stretching machine

In short, the functions of breathable film are: water resistance and breathability (moisture).

Due to the structural characteristics of the breathable film, it also has a barrier effect on other liquids, dust, and bacteria, giving it a wider application space.

How does the breathable film achieve its breathable function?

Taking the commonly used PE as a carrier for breathable film as an example.

Basic film-forming principle: PE+CaCO3- film-forming - stretching - breathable film

Breathability refers to the ability of a gas (vapor) to penetrate a material under certain conditions.

There is almost no complete literature on the breathability and water blocking principle of breathable membranes introduced through normal channels in foreign countries, so the opinions on them are also different. The following is our conclusion drawn through research and experiments, which has been recognized by our domestic and foreign peers!

PE breathable film is made by blending around 50% special calcium carbonate into LDPE/LLDPE polyethylene resin carrier, extruding it into a film, and then stretching it at a certain rate. Due to the fact that polyethylene resin is a thermoplastic material that can be stretched and crystallized under certain conditions, the interface between the polymer and calcium carbonate particles peels off during stretching, forming interconnected and winding pores or channels around the calcium carbonate particles. It is these pores and channels that endow the film with breathable (wet) function, thereby communicating the environment on both sides of the film.

When the concentration of water vapor on one side of the film is greater than the environment on the other side, a humidity gradient pressure difference is formed, which provides the basic conditions for gas (vapor) convection. Due to the formation of convection, the humidity environment on both sides of the film tends to be relatively balanced.

It is worth mentioning that when using breathable film as a waterproof film, the basic requirement for it is the blocking effect on the liquid. Only on this premise can we talk about breathable performance!