Why does the color of PET film turn yellow or gray or have yellow bars-technical knowledge

Why does the PET film turn yellow or gray or have yellow bars? Source: Protective film factory direct sales Release time: 2019-04-29 Click: 1846 PET film, especially when it is rolled into a reel, the color turns yellow or gray Phenomenon. It can be seen with 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. Foshan polyva Material specializes in the production of PET film, you are welcome to buy