Wisdom For Polyethylene vol.10
10. Measurement of Particulates in Liquids
2024-10-15
In the management of additives in polyethylene bags, "measurement of particulates in liquids" is a highly reliable evaluation method.
This article introduces an overview of this method, practical examples, and simple check procedures.
This article introduces an overview of this method, practical examples, and simple check procedures.
How to Identify Additives Adhering to the Bag
It is important to know how to check additives that are powders adhering to the bag. Most additives are not water-soluble. The bag is filled with water, and the additive adhering to the inner surface of the bag is mixed into the water, which is then measured with a liquid particle counter to make a determination.
This method is used in the incoming inspection of plastic bags, particularly by pharmaceutical manufacturers. In the past, we have measured several million particles (between 2 µm and 40 µm) on the entire inner surface of normal LLDPE bags.
Contamination Example in Pickling
Therefore, when cucumbers, Chinese cabbage, etc. are pickled in plastic bags together with ‘asazuke-no-moto’ (seasoning for easy pickling), which is often advertised on TV, the above-mentioned fine particles adhere to the pickles. Even if the vegetables have been grown organically and without pesticides, the result is that they are definitely contaminated during the pickling process.
Practical Confirmation Method
A confirmation method that can be experimented with in your company (especially for anti-static types): If you fill a plastic bag with tap water, shake it, and leave it for a few minutes so that air bubbles disappear, then check the water in the bag under a fluorescent light, you can easily see sparkling reflective substances. In the case of anti-static types, foaming may also be observed.
Typical Additives
Finally, other typical additives include:
- Ultraviolet absorbers (polyethylene bags that reduce the transmission of ultraviolet rays)
- Anti-corrosion agents (plastic bags for packaging metal machinery and parts)
- Anti-fogging agents (plastic bags for packaging vegetables, etc., which prevent water droplets from forming on the inner surface of the bag)
- Antimicrobial agents (silver zeolite or organic antimicrobial agents kneaded into the bag to create an antimicrobial effect)
Basically, any additive can be kneaded into the bag, and as long as it is heat-resistant, it can be produced, so there is a possibility that a wide variety of additives will be kneaded into the bag in the future. However, while organic types can be used, the adverse effects of the above-mentioned bleed-out must also be taken into consideration.
Summary
When bleed-out occurs, additives may emerge on the surface of polyethylene bags, potentially causing unintended substance migration. Therefore, careful management is required, especially for food and pharmaceutical applications.
It is important to continue evaluating the effects and safety of additives and to establish more appropriate management methods in the future.
It is important to continue evaluating the effects and safety of additives and to establish more appropriate management methods in the future.
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11. Microbial Risk on Poly Bags