Classification of lubricants
2021-08-18
In the plastic molding process, lubricants reduce the friction between the plastic and processing machine, and between the plastic particles, and they are therefore effective for improving the fluidity and mold-release properties of the plastic, and for enhancing the processing efficiency and appearance of the resulting molded article. Some act as external lubricants, and some are effective for improving internal lubricity; typically, both types are used in combination.
Hydrocarbon Lubricants: Paraffin Wax, Synthetic Polyethylene, and Liquid Paraffin
These are typical external lubricants and are chemically stable.
Fatty Acids and Higher Alcohols: Stearic Acid, Behenic Acid, 12-Hydroxystearic Acid, and Stearyl Alcohol
Fatty acids act as external lubricants, while alcohols act as internal lubricants.
Fatty Acid Amides: Stearic Acid Amide, Oleic Acid Amide, Erucic Acid Amide, Methylenebis (Stearic Acid Amide) and Ethylenebis (Stearic Acid Amide)
The acid amides are used for polypropylene (PP) and polyethylene (PE), while the alkyleneamides are used for polyvinyl chloride (PVC), polystyrene (PS), and acrylonitrile butadiene styrene (ABS).
Metallic Soaps: Ca, Zn, Mg, and Pb salts of Stearic Acid
These are used not only as lubricants but also as stabilizers for PVC. In polyvinyl chlorides, the Zn and Pb salts are used as external lubricants, and the Ca and Mg salts are used as internal lubricants.
Esters: Glycerin Monostearate, Glycerin Monooleate, Butylstearate, etc.
These possess both internal and external lubricity.
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