A packaging bag that bought the blown film of PBAT, a degradable material. He reported to the editor that he used the PBAT pure resin blown film of a certain manufacturer and found that there were black spots. The editor asked the industry experts what the reason was and how to deal with it, and the reply is as follows.
There are several reasons for black spots:
One is that the material itself contains impurities. Check whether there is a broken bag and whether there is debris mixed in.
If the package is not broken, check whether there are black spots in the material itself. There are so many black spots in the video. If it is a problem with the raw material, you should be able to see it with the naked eye.
If there are no black spots on the particles, dry the material (bake at 60 degrees for 2 hours) and do it again to see if there are any problems.
The second is the residue in the screw, which is not cleaned. Use PBAT resin to wash the machine at 160±10°C. Small machines generally need to wash 1 to 2 packs of materials, and large machines generally need to wash 3 to 4 packs of materials.
The third is the influence of temperature and plasticization, with carbonization or agglomeration cross-linking. Operate and debug according to the manufacturer’s temperature guidance.
The film is blown with PBAT pure resin, which is generally very transparent and will not have black spots.
If the film is blown with the same brand of PBAT, there will be black spots after using it, then it is mostly the problem of the raw material itself and there are impurities.
Judging from the video, the black spots are impurities that have not melted away. It should be a problem with the machinery and equipment. The carbonized substances are hidden in the gaps, and a little bit will be brought out every time, turning into black spots. Moreover, the degraded material is not resistant to high temperature, and the degraded material stays in the screw for too long, and it is easy to be carbonized. In addition, the starch is also easy to carbonize. Therefore, the machine must be cleaned every time during production.
Experts also suggested that the direct use of PBAT pure resin to blow the film is not stable enough, it is best to use the improved PBAT blown film material, because PBAT is too soft, adding PLA and filler compound modification.
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