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Few Additives are discussed with their Functions below:
Pigments / Colorants: They are used to increase the aesthetic of plastic products.
They are available in solid and liquid forms in various shades. They affect the heat
stability, light fastness, brightness and transparency of the product. Colours can be
opaque, transparent, pearlescent and special effects.
Slip additive: Polyolefins have a high COF which leads to a tendency to adhere to
themselves and to metal surfaces during processing. Slip additives are added to
reduce surface COF enhancing their processing and end applications. Fatty acid
amides are most commonly used as slip additives. Slips are generally used in
combination with antistatic and antiblocks in the film industry.
Anti Slip agents: These increases the surface COF of films used for lamination and
adhesion.
Antiblock additive: Polyolefin and other plastic films have a tendency to adhere
together or 'Block', often making it difficult to separate film layers, open plastic bag
or find the end of the roll. Film surfaces, copolymers, static electricity, corona
treatment, high temperatures, high pressure during winding and during storage - all
of these have an influence on blocking capabilities. Antiblocking additives,
generally inorganic mineral fillers are added to the plastic to minimise this adhesion.
These additives create a micro rough surface which reduces the adhesion between
film layers and lowers the blocking tendency.
Antistatic agents: Static Electricity builds up surface on plastics films which are
insulators due to the sliding, rubbing, or separating of a material. Consequences of
such charge build up includes dust pick-up on finished articles, poor printability of
product, sticking of film surfaces together, shocks to operator and possibility of
spark discharge leading to serious fire or explosion. To prevent static build up
Antistatic additive material are added during processing or compound. Its role is to
make the surface or the material itself slightly conductive, either by being
conductive itself, or by absorbing moisture from the air. They slowly migrate to the
surface; absorb moisture from the ambient air and builds up a conductive path on
the polymer's surface. This conductivity is not permanent and depends on initial
loading, rate of migration to surface and relative humidity also has a major effect on
surface resistivity.
Antioxidants: They provide thermal protection preventing "oxidation", the polymer
reacting with oxygen. Oxidation can cause loss of impact strength, elongation,
surface cracks and discolouration. Antioxidant also acts as stabilizers preventing
thermal oxidation reactions when plastics are processed at high temperatures and
light-assisted oxidation when plastics are exposed to UV light. Typically antioxidant
is required at about 0.1-0.25% of polymer weight and is incorporated by polymer
producers after the completion of polymerization process and before melt
homogenization to form pellets. Types of antioxidants are:
i) Primary antioxidants - These interrupt the primary oxidation cycle by removing
the propagating radicals. Such compounds are also called Chain Breaking
Antioxidants and examples include the hindered phenols and aromatic amines.
ii) Secondary antioxidants - These compounds are also called Preventative
Antioxidants as they interrupt the oxidative cycle by preventing or inhibiting the
formation of free radicals.

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