The phenomenon of composite white spots on the surface of PE protective film and the countermeasures
Nov 17, 2022
The phenomenon of compound white spot is very easy to occur on the PE milky white film. Generally, the milky white film is added with a certain amount of white masterbatch, namely: concentrated titanium dioxide. Due to the different quality of the color masterbatch, the particle size and hardness of the titanium dioxide contained are different, resulting in different quality and surface brightness of the opal white film produced after compounding. If the surface of the milky white film feels rough and has pockmarks from the side, most of the products compounded with such a film will appear white spots. Usually the solution to this problem is as follows: First, increase the coating amount of the adhesive. The second is to reprint a layer of white ink. No matter which method is adopted, the cost will be increased, so the PE film must be strictly inspected before use.
After compounding, the phenomenon of astringency in the finished product has occurred in many manufacturers. The automatic packaging machine for the compounded product is not running smoothly, or the bag produced is difficult to open.
Dry compounding generally uses a two-component reactive adhesive, which is cured at high temperature after compounding to achieve the highest compound strength. The slip agent in the PE film will change due to the change of curing temperature. At a certain temperature, the slip agent will undergo chemical changes and lose its smooth effect. The higher the temperature, the greater the change and the loss of the slip agent. The larger the amount, the final result will be a sticky product that cannot be used. Therefore, the temperature of the curing chamber must be strictly controlled at about 40 °C, and cannot be increased arbitrarily. In addition, according to the different uses of the product, different ingredients should be selected to avoid the astringency of the product caused by the improper selection of resin grades.
After compounding into the last process or into the hands of customers, sometimes the local heat sealing temperature is too high, the heat sealing is not good, etc., and it cannot be saved in serious cases. The reasons for this result include corona breakdown, high content of slip agent, and excessive addition of recycled materials.
