ASTM D938 – Congealing Point of Petroleum Waxes Including Petrolatum
Petroleum waxes are typically high molecular weight compounds that are water-insoluble and solid or semi-solid at room temperature. They include microcrystalline waxes (used in anti-friction coatings), paraffin waxes (used in chain lubricants and mold release agents) and petrolatums (used in anti-seize compounds and tape coatings). The congealing point (the temperature at which the wax ceases to flow) gives valuable information needed in formulating products. It may also give an indication of wax purity. This test determines the congealing point of waxes.
A thermometer is thermally stabilized in a melted wax sample. Upon withdrawal, the wax coated thermometer is slowly rotated and observed while cooling in air. Reported is the temperature at which congealing of the wax coating is observed.