METHOD OF DETERMINING THERMAL VOLUMETRIC EXPANSION OF PARAFFINS AND WAXES Russian patent published in 2025 - IPC G01N25/16 G01N25/02 G01N33/44 

FIELD: measuring.

SUBSTANCE: invention relates to thermal testing of paraffins, ceresins and paraffin waxes used as solid fillers in sensors for automatic temperature control of heat-and-power objects for various purposes. Disclosed is a method for determining thermal volumetric expansion, based on the use of a pycnometric type dilatometer, consisting of a graduated capillary tube and a reservoir, in which the working transfer liquid and solid samples of the test paraffins, ceresins or paraffin waxes are placed. To prevent dissolution of samples of paraffins and waxes when they are heated in the working fluid, a mixture of glycerine and water in weight ratio of 1.0:1.0 is used as the working fluid. Method is intended for determination of volumetric expansion of paraffins, ceresins or paraffin waxes having density less than density of working transfer fluid. To prevent the samples from floating in the working fluid and clogging the capillary, the tested paraffins or waxes are weighted by mixing with aluminium powder in ratios that ensure their stability and increase in density higher than that of the working transfer fluid. Aluminium powder also increases heat conductivity of the test samples, which speeds up the process of their melting. To obtain reproducible volumetric expansion, samples of paraffins, ceresins or paraffin waxes are subjected to hot heat treatment until they are completely melted at a temperature higher than the melting point of the most high-melting component included in the samples. To obtain a reproducible crystalline structure, samples of paraffins, ceresins or paraffin waxes are subjected to cold heat treatment at a temperature below the melting point of the lowest-melting component of the samples. In order to detect phase transitions and phase states in samples, optimum ratios between the sample and the aluminium powder, the sample weight and the heating rate of the dilatometer are selected. According to dependences of volumetric expansion of samples of paraffins, ceresins or paraffin waxes on temperature ΔV/V₀=ƒ(t) determined is temperature range Δt_i of phase states of samples. For samples of paraffins, ceresins or paraffin waxes, their volume expansion coefficients are calculated by the ratio k_i=ΔV_i/(V₀∙Δt_i), where ΔV_i is change in volume of samples for temperature regions of phase states Δt_i relative to their initial volume V₀.

EFFECT: high accuracy of determining temperatures of phase transitions and temperature regions of phase states.

2 cl, 5 dwg, 4 tbl