Automated Viscosity and Density Measurements of Microcrystalline Waxes
Microcrystalline waxes must meet a number of specifications when produced in refineries. Among many other parameters, viscosity plays an important role. The Anton Paar SVM 3001 viscometer in combination with the heated sample changer Xsample 630 allows fully automated viscosity and density measurements of those waxes.
In the following sections we present a fully automated system using the heated sample changer Xsample 630 for filling and cleaning combined with an SVM 3001 viscometer for measuring the viscosity and density of microcrystalline waxes.
Definition of waxes
The definition of the German Society for Fat Science is widely used. According to this definition, a substance is called a wax if it is kneadable at 20 °C, solid to brittle-hard, translucent to opaque in color but not glassy, melts above 40 °C without decomposing, is slightly liquid (low viscosity) just above the melting point, has a strongly temperature-dependent consistence and solubility, and can be polished under slight pressure. If more than one of the above properties is not fulfilled, the substance is not a wax according to this definition .
Fossil waxes obtained from petroleum are paraffins, which are subdivided into macrocrystalline and microcrystalline paraffins. Depending on the degree of refinement, they can have widely varying degrees of hardness and melting points from liquid to solid .
Microcrystalline waxes are a special form of paraffins in which the particle size is greatly reduced down to a grain size limit of about 30 μm .
In contrast to the more familiar paraffin wax which contains mostly unbranched alkanes, microcrystalline wax contains a higher percentage of iso-paraffinic hydrocarbons and naphthenic hydrocarbons. It is generally darker, more viscous, denser, tackier and more elastic than paraffin waxes, and has a higher molecular weight and melting point .
Microcrystalline waxes are widely used as additives for wax mixtures e.g. for wood chip and fiberboard production, production of Vaseline, lubricants, release agents in rubber articles and tires, firelighters, for the refinement of papers and cardboard, such as frozen food packaging, candy wrappers or drinking cups, and especially for the production of candles. They are also used in chewing gum, glue waxes, cheese waxes and cosmetic products .
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