Effect of Curing and Sintering Temperature of Waterproof and Breathable Membrane

As the heat-setting temperature increases, the thickness of the film decreases gradually. The waterproof and breathable film manufacturer tells you that this is because the microfibers and nodes will fuse and shrink during heat setting, which will reduce the voids in the thickness direction inside the film, thereby reducing the thickness of the film. And the higher the temperature, the more severe the shrinkage of the microfibers and the knots, and the more the thickness of the film is reduced.

The pore size, thickness, bow deformation and thermal shrinkage of the film are all affected by the heat setting temperature, but their laws are different. At the same time, during the processing of PTFE film, as the setting temperature increases, the crystallinity of PTFE tends to decrease, which in turn affects the moisture permeability and mechanical properties of the film. When the heat setting temperature is increased, the crystallinity of PTFE decreases, the pore size of the film becomes larger, and the moisture permeability increases, but the breaking strength decreases. Therefore, in order to obtain a film with excellent structural properties, the heat setting temperature should be selected according to the application of the film.

Effect of curing and sintering temperature

Curing is usually carried out under some tension to ensure pore formation and dimensional stability of the film. The curing temperature has a great influence on the pore size and porosity of the film. Other process conditions are fixed (the width is kept at 1.5m).

With the increase of curing temperature, the pore size and porosity of the film increased, but the number of pores decreased. The reason may be that with the increase of temperature, the crystallinity of the film decreased and the amorphous region increased. The pore formation of the film occurs in the amorphous region, and the increase of the amorphous region provides space for the development of the pore size. From the scanning electron microscope photo, the film cured at a higher temperature has large nodes and wide distances between nodes. , the nodes are connected to each other by fibrils in the membrane, the space between the fibrils is the hole, and the membrane aperture is the result of the crisscross stacking of the fibrils, and the size of the void between the fibrils determines the aperture size. The manufacturer of the waterproof vent valve tells you that the number of nodes per unit volume is small, the gap between the fibrils is large, and the aperture will inevitably increase. High temperature curing may also cause some fibrils to break, further increasing the pore size and reducing the number of pores.