PVC lubricants are classified according to their source, and there are four main types—petroleum waxes, synthetic hydrocarbon waxes, mineral waxes, and some natural vegetable-based triglycerides.
There are two kinds of petroleum wax.
1, Paraffin wax (coarse-crystalline, mainly contains linear alkanes in the C20 to C40 range, hard and brittle, with a melting point in the range of 45 – 70 degrees Celsius.
2, Microcrystalline waxes, which contain large amounts of cyclic and branched paraffins in the C30 to C80 range, are soft, tough and have a high affinity for oils. They melt in the 45 to 70 degrees Celsius range. Petroleum waxes for PVC also include waxy petroleum, which acts as an excellent external lubricant.
There are basically three basic types of synthetic hydrocarbon waxes used in PVC. Including polyethylene wax, oxidized polyethylene wax and china synthetic paraffin wax, also known as Fischer-Tropsch wax. Polyethylene waxes have a melting point range of 98 – 115 degrees Celsius. Their oxidation leads to chain scission at their branch points, resulting in a variety of oxygenated products, including acids, alcohols, esters, aldehydes, ketones, and hydrogen peroxide. The resulting oxidized polyethylene wax is more polar, more compatible with PVC, and acts as a film former in the PVC melt. Fischer-Tropsch waxes are microcrystalline, water-white solids, oil-free, hard and have a high melting point. They are usually mixed with natural paraffin to increase the melting point. Fischer-Tropsch waxes are preferred for cable and wire production due to their better dielectric constant, electrical resistance and electrical breakdown strength compared to other petroleum waxes.
Mineral wax is mainly derived from montan wax, which is a vegetable wax fossil. Over the past few years, montanic acid and its esters and soaps have been widely used in PVC for high-tech plastic lubricant applications. Their combination of high molecular weight, film-forming properties and plating resistance is unmatched by alternative lubricants. Ethylene glycol montanate and partially saponified 1,3-butanediol montanate are representative of montan waxes.
PVC lubricants produced from naturally occurring triglycerides can be considered derivatives of 1-octadecanoic acid, commonly known as stearic acid, a linear saturated carboxylic acid with 18 carbon atoms. Stearic acid can be converted into a variety of lubricants. In many cases, it can be found in complex ester lubricants on the market.
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