Managing Dual Use Additives Information Flow in Plastic Packaging Declarations
Dual use additive management demands specific identity flow from resin compounders to food packers to satisfy direct food additive maximum limits.
E 551
Meaning
Synthetic amorphous silica particles act as anti-blocking agents to prevent the sticking of film layers and smooth the flow of resin pellets. The identifier e 551 is the food grade classification for silicon dioxide used in packaging materials. Tiny particles create a micro-rough surface on the polymer to reduce the contact area between two adjacent layers.
Surface Texture
Microscopic protrusions created by the additive prevent the formation of a vacuum between flat surfaces. When e 551 is included in a film recipe, it creates a slight haze that is often acceptable in industrial packaging. The size of the particles is chosen to match the thickness of the film.
Particle diameter must be uniform to avoid creating stress points in the thin membrane.
Optical Clarity
Choice of refractive index allows for the maintenance of transparency in high quality packaging. High purity e 551 has a refractive index very close to that of common polyolefins. Light scattering is minimized to preserve the aesthetic appeal of the contents.
Moulders select specific grades to balance the need for easy handling with the visual requirements of the customer.
Block Resistance
Mechanical separation between layers is the primary function in thin gauge applications. Without the presence of e 551, high pressure in a storage roll can fuse the layers together in a phenomenon known as blocking. Blocked rolls render the material unusable for automated filling lines.
Separation gaps allow the film to slide and separate during high speed processing.