???????There are three main cases of perforation: the material is too dirty, the filter screen is not fine enough; the four-roll calender has cold material mixed in; the effect of filling material and plasticizer.
???????Case 1: It can be solved by increasing the fineness of the filter and changing the frequency of the filter; if there are still perforations, consider replacing the material.
???????Case 2: It can be solved by controlling the stocking between the rollers; in addition, the material should be plasticized as much as possible to avoid mixing of unplasticized raw materials, and the speed ratio of each machine should be controlled to reduce this as much as possible. 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 experienced by the ordinary calendered film is unidirectional, smaller than that of the uniaxially stretched film, and can be compensated to some extent by the calendering device . The biaxially stretched film is stretched in two directions, which is much larger than bidirectional stretching. If a 2m wide film is stretched to 5m, the hole with a stretch ratio of 215.1mm becomes 215mm after stretching. In fact, the hole is larger than 215mm, because the stress concentration around the hole is susceptible to damage. Therefore, it is very important to solve the perforation problem of stretched film.
???????Case 3: The filling material mainly uses light calcium carbonate. The appropriate amount of calcium carbonate can increase the strength of the film, but when the amount of calcium carbonate reaches 50 to 60 parts (relative to 100 parts of PVC), the film tear strength is significantly reduced. The perforation of the stretched film increased significantly. Therefore, controlling the amount of calcium carbonate is also an important factor to reduce the pores of the stretched film. When the amount of plasticizer is increased, the holes are reduced due to the softening of the film and the increase in elongation at break, otherwise, the holes are increased.