wax (petroleum)

is any of a range of relatively high-molecular-weight hydrocarbons (approximately C16 to C50), solid at room temperature, derived from the higher-boiling petroleum fractions. There are three basic categories of petroleum-derived wax: paraffin (crystalline), microcrystalline and petrolatum.

Paraffin waxes are produced from the lighter lube oil distillates, generally by chilling the oil and filtering the crystallized wax; they have a distinctive crystalline structure, are pale yellow to white (or colorless), and have a melting point range between 48°C (118°F) and 71°C (160°F). Fully refined paraffin waxes are dry, hard, and capable of imparting good gloss.

 Microcrystalline waxes are produced from heavier lube distillates and residua (see bottoms) usually by a combination of solvent dilution and chilling. They differ from paraffin waxes in having poorly defined crystalline structure, darker color, higher viscosity, and higher melting points — ranging from 63°C (145°F) to 93°C (200°F). The microcrystalline grades also vary much more widely than paraffins in their physical characteristics: some are ductile and others are brittle or crumble easily. Both paraffin and microcrystalline waxes have wide uses in food packaging, paper coating, textile moisture proofing, candle-making, and cosmetics.

Petrolatum is derived from heavy residual lube stock by propane dilution and filtering or centrifuging. It is microcrystalline in character and semi-solid at room temperature. There are also heavier grades for industrial applications, such as corrosion preventives, carbon paper, and butcher’s wrap. Traditionally, the terms slack wax, scale wax, and refined wax were used to indicate limitations on oil content. Today, these classifications are less exact in their meanings, especially in the distinction between slack wax and scale wax.

Also see blocking point, chlorinated wax, gloss, laminating strength, melting point of wax, oil content of petroleum wax, paraffin wax, petrolatum, refined wax, scale wax, scuff resistance, sealing strength, slack wax, strike-through.

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