Sibelite grades exhibit strong infrared reflection properties in the IR-range. When used in agricultural film applications this property allows for a reduction in heat loss during dark hours, which provides additional benefits like optimal growth, an extended growing season and a reduction in heating cost.
Sibelite grades are highly effective additives in changing the asperity of the surface of plastic agricultural films hereby reducing the tendency of plastic films to stick together when brought together. This phenomena, also known as blocking, is a non-desirable effect in the processing of the film as well as during installing of the film in the field or as coverage for “glass”-houses.
To overcome the blocking phenomenon, Sibelite additives may be added to create a micro surface roughness with particles protruding from the smooth film surface.
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,
- Efficiency of the anti-blocking additive 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
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Sibelco offers a range of fillers 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: