DSC in a convenient and rapid method for determining the temperature limits within which a wax undergoes during transitions. The highest temperature transition is a solid-liquid transition associated with complete melting; it can guide the choice of wax storage and application temperatures. The solid-solid temperature transition is related to the properties of the solid, that is, hardness and blocking temperature.
Note 28212;For a relatively narrow cut petroleum wax, the lowest transition will be a solid-solid transition. A narrow cut wax is one obtained by deoiling a single petroleum distillate with a maximum range of 120°F between its 5 % and 95 % vol in accordance with Test Method D1160 boiling points (converted to 760 torr). The DSC method cannot differentiate between solid-liquid and solid-solid transitions. Such information must be predetermined by other techniques. In the case of blends, the lower temperature transition may be envelopes of both solid-liquid and solid-solid transitions.
Since petroleum wax is a mixture of hydrocarbons with different molecular weights, its transitions occur over a temperature range. This range is one factor that influences the width, expressed in °C, of the DSC peaks. The highest temperature transition is a first-order transition. If, for a series of waxes, there is supporting evidence that the highest temperature transition of each wax is the major first-order transition, its relative width should correlate with the relative width of the wax's molecular weight distribution.
1.1 This test method covers the transition temperatures of petroleum waxes, including microcrystalline waxes, by differential scanning calorimetry (DSC). These transitions may occur as a solid-solid transition or as a solid-liquid transition.
1.2 The normal operating temperature range extends from 15°C to 150°C (Note 1).
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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