Solutions to different crystal points of PE protective film
Jan 12, 2022
We introduced in detail the main crystal point types, identification methods, causes and countermeasures. Summarized as follows:
①Identify different types of crystal points by using a hot stage polarizing microscope
The contaminants can be seen under the microscope—the crystal points of foreign contaminants;
After the main body of the film is heated and melted, clear crystal points or degradation products-highly cross-linked/oxidized crystal points can still be seen;
The crystal points disappear after the main body of the film is heated and melted, but the crystal points can be seen again after cooling down—the slightly cross-linked crystal points;
The crystal points disappear after heating and melting the main body of the film, but the crystal points do not recover when the temperature is lowered—the crystal points that are poorly plasticized.
②Responding to the crystal points of foreign pollutants
Improve the cleanliness of the workshop;
Improve the material storage and transportation process and keep the resin packaging bag clean;
Strictly control the production order and avoid cross-contamination between different types of raw materials when preparing ingredients.
③Responding to cross-linking/oxidizing crystal points
Replace the batch of raw materials with fewer crystal points;
Reduce processing temperature;
Add additional antioxidants;
Optimize the equipment, replace with a screw with excellent design, etc.
④How to deal with poor plasticizing crystal points
Avoid mixing pellets and powders;
Pay attention to the pumping process of raw material particles to avoid the generation of raw material powder due to friction;
Avoid simply blending raw materials with very large differences in melting point;
If required by the formula, raw materials with large melting points must be mixed; the temperature in the first zone and the second zone of the screw needs to be lowered to avoid premature melting of low-melting raw materials. At the same time, the filter screen can be encrypted to increase the shear in the metering section.
