Problems needing attention in the perforation of PVC protective film
Nov 02, 2022
There are three main types of perforation:
1. The material is too dirty and the fineness of the filter screen is not enough;
2. The four-roll calender is mixed with cold material;
3. The influence of filling materials and plasticizers.
Case 1 can be solved by increasing the fineness of the filter screen and replacing the filter screen frequency; if there are still perforations, consider replacing the material.
Case 2 can be solved by controlling the material storage between the rollers; in addition, the material should be plasticized as much as possible to avoid the mixing of unplasticized raw material, and the speed ratio of each machine should be well controlled to minimize the resulting hole problem.
The perforation of the stretched film is much more obvious than that of the ordinary calendered film, because the stretching force of the ordinary calendered film is unidirectional, which is smaller than that of the uniaxially stretched film, and can be compensated to a certain extent by the calendering device . The stretching force of the biaxially oriented film is bidirectional, which is much larger than that of biaxial stretching. If the film with a width of 2m is stretched to 5m, the hole with a stretching ratio of 215.1mm will become 215mm after stretching. In fact, the hole is larger than 215mm, because the stress around the hole is concentrated and it is easily damaged. Therefore, it is very important to solve the problem of perforation of stretched films.
Case 3 The filling material mainly uses light calcium carbonate. An appropriate amount of calcium carbonate can increase the strength of the film, but when the amount of calcium carbonate reaches 50~60 parts (relative to 100 parts of PVC), the tear strength of the film is significantly reduced, and the stretching The perforation of the film was significantly increased. Therefore, controlling the amount of calcium carbonate is also an important factor in reducing the pores of the stretched film.
When the amount of plasticizer increases, the pores decrease due to the softening of the film and the increase in elongation at break, and vice versa, the pores increase.
