Minbloc grades are highly effective additives in changing the surface of plastic films hereby reducing blocking, the tendency of plastic films to stick together when brought together. This is a non-desirable effect in the processing of the film as well as during use of the film or the plastic bags made herewith.
To overcome the blocking phenomenon, MINBLOC® additives may be added to create a micro surface roughness with particles protruding from the smooth film surface.
Without MINBLOC® With MINBLOC®
When selecting an anti-blocking additive the following criteria need to be carefully considered:
- Good compatibility between the anti-blocking additive and the resin (PE, PP, PVC, PET, PA) in which it will be used
- Refractive Index of the anti-blocking additive as close as possible to that of the resin ensuring optimal optical (clarity, picture right and haze, picture left) properties of the film
- Compliance with global food regulations
- Efficiency of the anti-blocking as measured by the coefficient of friction (CoF) – this is often determined for the anti-blocking additive in combination with an anti-slip agent. There is a static and dynamic CoF
- Size of the mineral particle in relationship with the thickness of the film – particle size is indicated by d50
- Surface area (porosity) of the particle: lower surface area (porosity) leads to higher loading of the anti-blocking additive in a masterbatch and also to more efficiency of the lubricant or slip-agent when added to the same masterbatch – surface area is indicated by BET or OAN
- No negative impact on the mechanical properties of the film
- Hardness of the mineral particle – abrasion during processing
Sibelco offers a range of Minbloc grades based on different minerals to allow the film-processor to make the proper selection for the specific requirements of the film given the above criteria:
|Minbloc HC||Nepheline Syenite||Globally|
|Minbloc MC||Microcrystalline Silica||Globally|