Why do impermeable membranes form odor? This is because the temperature of the extruder or the temperature of the resin is too high, causing the taste decomposition of the resin to be too large, and the oxygen-containing groups on the surface of the resin are oxidized to form the taste of the composite film. The extruded composite film has a taste; the bottom coating uses a high boiling point, non-volatile solvent, which causes the composite film to have a taste.