Analysis of common quality problems of PET film! -technical knowledge

Analysis of common quality problems of PET film! Source: Protective film factory direct sales Release time: 2019-03-02 Click: 2805 The color of the PET film is yellow or gray or has yellow strips, especially when it is rolled into a reel, the color is yellow or gray. Use It can be seen by the naked eye. If there are yellow bars, you must unfold the film or observe the light. Or spread it on a white backing for better identification. Analysis of the cause The reason is the same as the gel point, yellow point and black point. Yellowing is caused by poor thermal oxygen stability of the resin or more air entering the extruder. When the resin is thermally oxidized, it produces a large amount of acetaldehyde. Because acetaldehyde reduces the antimony trioxide to antimony, the film (resin) turns gray. The appearance of yellow bars usually occurs after replacing the filter or after replacing the resin. The reason is that there may be air in the person during the replacement. , Or part of the resin stays in the machine for too long. It makes part of the resin yellow, and after the formation of these yellow resins, it is impossible to fully mix with the normal melting and plasticization, so yellow bars appear. 2. Static electricity One characteristic of excessive static electricity is adsorption. Rubbing the surface of the PET film, or peeling off the film roll, or when the film is running at high speed, will generate static electricity. If there is dust, paper dust, hair, etc. near the film at this time. It may be adsorbed and affect the quality of the product film (especially the capacitor film). When the static electricity is serious, it may also cause fires, electrical accidents and other accidents. It is known that the static electricity of the polyester film is too large, which will affect the subsequent processing and processed products. Undesirable effects, for example, the electrostatic size of the bonded PET film can be determined by an electrostatic tester at about 500v. The measurement shows that the electrostatic size of the two sides of the film is also different. The reason is that the PET film is a polar electrical insulating material, which makes it through friction The charge generated by the action of, shearing, etc. cannot be transferred away, and accumulates on its surface to form static electricity. The size of the static electricity of the PET film is related to the electrical properties of the resin body, the application of additives, and the film making process. Because they directly affect the surface of the film/ The structure and properties of the surface, such as the crystallinity of the surface layer, the number of polar groups and their orientation, the size of the contact area of u200bu200bthe two films, and other factors that affect the formation of static electricity. Based on this, it can also explain why the static electricity on both sides of the film is different. Solution a. Find out the reasons from the resin, additives, and process and solve them in a targeted manner; b. Use static eliminator C in film making and post-processing of the film, coat a conductive layer on the surface d, use antistatic agent/resin 3. The bonding strength of printing, compounding and aluminizing is not enough. For the box bonding strength of printing, compounding and vacuum aluminizing, self-adhesive tape is usually used as the inspection side. There are 3 types of quiet conditions: full peeling, partial peeling and non-peeling. Both of the two types are of insufficient drilling strength. The reason analysis is that the strength of the combination of PET film, ink and mink mixture is restricted by the surface tension of the PET film. The surface tension of the untreated PET film is 42~48N/S, which cannot be reached. The adhesive strength of the ink adhesive is required, so it is important to take some measures such as corona treatment to increase the surface tension to reach 55N/cm or more.