METHOD OF DETERMINING THE DEGREE OF CROSS-LINKING WHEN EXAMINING CROSS-LINKED POLYCAPROLACTONES Russian patent published in 2020 - IPC G01N25/20 

FIELD: chemistry.

SUBSTANCE: invention relates to polymer chemistry, particularly to determination of degree of cross-linking. Method of determining the degree of cross-linking when examining cross-linked polycaprolactones involves comparing the characteristic parameter of the analyzed and reference samples and assessing the degree of cross-linking of the analyzed sample from the relationship between the known degree of cross-linking of the reference sample and its characteristic parameter on the calibration curves, for which a sample of cross-linked polycaprolactone in a nanogram amount is placed on a sensor chip of a fast scanning calorimeter, the sample is preheated to a temperature higher than the melting point followed by cooling, wherein the characteristic parameter used is a half-period of crystallization, to determine which after preliminary heating and cooling of the sample, the sample is heated rapidly to a temperature higher than the melting point at a rate of not less than 5,000 K/s; heated sample is cooled to minus 80 °C at a rate of not less than 5,000 K/s and held at minus 80 °C for 1 s; further heating is carried out to 0 °C at a rate of not less than 5,000 K/s; further holding sample at 0 °C for 0.01 s, then heated to temperature higher than melting point at rate of 1,000 K/s; then repeatedly repeating sequence of actions, starting from stage of sample cooling to minus 80 °C at a rate of not less than 5,000 K/s and finishing stage of heating above melting point at rate of 1,000 K/s, wherein at the sample holding step at 0 °C, the hold-up time is varied during each repetition of the sequence of actions – 0.02; 0.05; 0.1 s and further linearly on a logarithmic scale to 500 s; then calculating total latent enthalpy of fusion at all times of aging by integrating obtained calorimetric heating curves; further, calculating a ratio of total latent enthalpy of fusion at given exposure time to maximum possible total latent enthalpy of melting for said sample; further determining the half-period of crystallisation t_1/2, corresponding to the hold-up time required to achieve a degree of crystallinity of polymer of 50 %; then, the degree of cross-linking of the analyzed sample is determined from a calibration curve in coordinates lg(t_1/2) – degree of cross-linking N [mol/cm³], based on analysis of reference samples.

EFFECT: determining cross-linked polycaprolactone cross-linking ratio using a minimum amount of polymer sample, as well as reducing time and achieving high accuracy of determination.

1 cl, 5 dwg