METHOD FOR DETERMINING CHANGES IN OXIDATION RESISTANCE OF THERMALLY STABILIZED POLYMERS AND PREDICTING THE RISK OF ITS REDUCTION DURING THERMAL AGING Russian patent published in 2021 - IPC G01N25/00 

FIELD: polymer materials.

SUBSTANCE: invention relates to the field of analytical methods to study the behavior of thermally stabilized polymer materials and predicting the stability of various thermal stabilizers in polymers with targeted properties. A method for determining changes in the oxidation resistance of thermally stabilized polymers and predicting the risk of its reduction during thermal aging includes thermophysical measurements using a calorimetric method of the heating process parameters of a stabilized polymer sample placed in a measuring chamber during the observation time, obtaining graphical dependences of the parameters of the status change of the test samples depending on the time and temperature of observation, - characterized in that measurements of oxidation induction time are preliminary taken: the time interval from the moment of the oxidizing gas supply to the recorded start of sample oxidation when heating various control samples of a stabilized polymer with the specified amounts of a heat stabilizer in each of them in an inert gas environment, for example, nitrogen, to a set temperature value - not higher than the polymer preparing temperature - and subsequent aging at this temperature in the oxidizing gas medium to obtain the calibration dependence of oxidation induction time of the concentration of heat stabilizer in the control samples, and then heating the sample under study of the stabilized polymer to determine the time of its oxidative induction, then take new samples of the specimen under study and heat them up first in inert gas to the temperature setpoint that is less than or equal to the calibration temperature and then allow the samples to stand for successive periods of time, during which partial evaporation of the heat stabilizer and its removal from the reaction space takes place, bring the samples to the calibration temperature and keep them in the oxidizer flotation to determine the oxidation time of the polymer with residues of the non-evaporated thermal stabilizer, and after that using the calibration curves, determine the concentration of the non-evaporated thermal stabilizer in the test samples, establishing the dependence of the concentration of the thermal stabilizer on the exposure time at a certain temperature and determine the effective rate constant of thermal aging. That is followed by building a linear dependence of the logarithm of the effective rate constant on the reciprocal temperature and determining effective activation energy of the thermal aging process based on the totality of the data obtained, and predicting the applicability of the thermal stabilizer, i.e. the possibility of obtaining a polymer with antioxidant resistance meeting the specified requirements that determine the performance properties of polymers.

EFFECT: technical result is ability to determine changes in the composition of the thermally stabilized polymer, namely, changes in the concentration of the evaporating thermal stabilizer for subsequent quantitative determination of the effective parameters of the thermal aging process.

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