First, the role of internal stress
We used PET/VMPET/PE structure as a small test. Generally, the PET printing surface was coated with the aluminized surface of VMPET, and then placed in the curing chamber. The cured aluminum layer showed no signs of transfer. Using the above composite film to coat the composite PE film, it was found that the aluminum plating layer of VMPET was transferred to the printing surface, which is a problem faced by most color printing factories.
Second, softness - release of internal stress
Not only the inconsistent stretching between the layers of the composite film produces internal stress, but also the internal stress is generated after the polyurethane adhesive is cured.
Third, the quality of the aluminized film itself
There are many transfer phenomena of aluminum-plated composite films in China, which have a great relationship with the quality and processing methods of aluminum-plated substrates. For example, for a CPP substrate for aluminizing, can a resin selected as a corona layer last for a corona effect? In addition to corona treatment, there is also an ion impact method to increase the surface tension of the CPP film. Different treatment processes make the aluminum plating layer very different in the performance of whether it is easily transferred. VMCPP generally has a shelf life of only 3 months, and the film-coated aluminum layer over a period of time is easily transferred. What is said here is the storage period calculated from the date of manufacture, and the date it is stored in the warehouse of the manufacturer and distributor is also counted. The climate is also a factor we consider, and the winter storage period can be slightly longer and the high-humidity summer should be shortened appropriately.