Have you ever asked yourself ...
...why it is so difficult to provide consistent slip properties in standard coex film?
Food contact regulations limit the range of chemicals to select from to modify the properties of plastic articles. Chemical agents modifying the slip properties may serve as an example to point out these limitations:
- Siloxanes provide good slip properties but interfere with printing, sealing, and metallizing in general
- Certain anti-blocking agents provide acceptable slip properties on their own or may at least be used as slip synergists but require a close control of the top layer thickness and –last but not least– are fairly expensive.
- So-called migratory additives like traditional amide slip agents tend to delay in performance occasionally.
Possibilities to control electro-static charging are even more limited. All systems compatible with the orientation process (and Food Contact Regulations) are migratory in nature and require exposure to a certain level of moisture to perform as required. This makes testing for anti-static properties fairly difficult in a typical Q-lab and the necessary conditioning of the film adds to the working capital costs.
For this, most BOPP manufacturers tend to add such additives generously, wasting money and, even worse, lay the seed for developing a "cloudy" and "greasy" appearance known as blooming and potential interference with the adhesion of metal layers (barrier film), printing inks, and adhesives. Optimizing additive incorporation is required.