Clarifying - Thermoplastic polymers, elastomers and additives

Nucleation agents are generally used to improve the formation of nuclei for the growth of crystals in the polymer melt. A higher degree of crystallinity and a more uniform lens. The structure in the hard phase can be obtained by adding a nucleating agent in the polymer.

The nucleating agents can be classified as inorganic additives (talc, silica), organic compounds (salts of mono or polycarboxylic acids) and polymers. Nucleation agents can be used to improve the crystallinity of a hard phase segment. This type of material is added to the semi-crystalline plastics before processing and manufacturing, affecting the speed of crystallization and the size of the spherulites, are called as nucleating agents. These are typically insoluble or immiscible materials that provide sites for crystal formation. The main benefit of the addition of nucleating agents is the improvement in cycle time during injection molding.

When the addition of nucleating agents decreases the size of crystallites below the wavelength of visible light, it refers to these agents as clarifying agents, since they reduce opacity and improve transparency.

For nucleation of nylon and PP, the traditional material of choice is sodium benzoate. The levels of use are in the order of 0.1%. Sodium benzoate does not impart any improvement in optical properties. Low molecular weight polyolefins, ionomers, as well as plasticizers such as epoxidized soybean oil are used for the nucleation of semicrystalline plastics such as PET. Modified benzylidene sorbitoles dominate the PP nucleation and clarification market. They are used in 0.1-0.3% levels in both homopolymers and copolymers for injection molding.