1. Temperature: The protective film of color steel plate is at 80 °C temperature. Due to the bubble, the protective film of color steel plate is propped up, and the protective film of color steel plate has begun to be slowly torn under high temperature condition. If the heat resistance or cohesion of the adhesive is not good, it is easy to appear residual glue or shadow around the bubble of the protective film of the color steel plate. Generally, the place where the shadow appears is the place where the bubble of the protective film of the color steel plate is formed.
2. Emulsifier: After the emulsifier migrates, there will be shadows. The surfactant will act as an external plasticizer in the coating film, making the film soft and elastic. This is advantageous if the plasticizer is evenly distributed during coating. However, due to the surface activity of the surfactant, the molecules migrate from the bulk phase and collect on the surface, and tend to be concentrated at the membrane-air interface, thus forming a shadow.
Note: The longer the time passes, the larger the contact surface of ordinary small bubbles with air, and the higher the possibility of forming a shadow. Therefore, when filming, try to avoid the generation of small bubbles, use a good quality, uniform coating of color steel plate to protect the film, which can delay the appearance of shadow.www.snpefilm.com