SU469077A1 - Method for determining the degree of swelling of polymers - Google Patents

Description

one

This invention relates to optical methods for analyzing polymers.

Methods are known for determining the degree of swelling of polymers in plasticizers by measuring the intensity of light reflected or passing through the sample under study.

These methods do not allow achieving high measurement accuracy and automating the recording of experimental data.

The proposed method differs from the known one in that the sample under study is subjected to heating, for example, using a heating table, and the monitoring is carried out using a polarization microscope and an apparatus for automatically recording the change in the intensity of a polarized light.

FIG. 1 is a flow chart illustrating the method described; in fig. 2 and 3 graphs.

The block diagram includes a polarization microscope 1 of the MIN-8 or MBI-6 type, a heating table 2 with a photoelectric sensor 3 of the FEU-19M type 3, electronic components including a stabilizer 4 and a rectifier 5 of the supply voltage, a photocurrent amplifier 6 and a self-recording potentiometer 7 EPP-09 type for automatic recording of the intensity of polarized light passing through the sample and the temperature of the sample.

2

The installation operates as follows. Polarized light passing through the sample is incident on the cathode of the photomultiplier. The emerging photocurrent is enhanced and can be

measured by visual microammeter. The ballast resistance is included in the microammeter circuit. The voltage drop across the ballast resistor, proportional to the photocurrent, is recorded by a multipoint potentiometer 6. The sample temperature is simultaneously recorded on the same potentiometer.

The design of the heating table allows research to be carried out in a wide

temperature range from -150 to 300 ° C.

In combination with the microscope 1, the installation allows simultaneous photographing of the structure of the sample in polarized light, which makes it possible to simplify the decoding of the obtained data.

An automatic installation can also be used to study the patterns of swelling of isotropic polymers that do not possess birefringence. In that

In this case, the device operates in a nephelometer mode, measuring the change in the optical density of the polymer dispersion in the plasticizer.

Using this method allows one to study the interaction of polymers with plasticizers at a constant predetermined temperature in order to determine the speed of the swelling process and its completion; the interaction of polymers with plasticizers when the polymer dispersion is heated at a certain rate in order to determine the gelation temperature; the effect of the composition, the properties of the plasticizer and the polymer, and the modes of their combination on the structural transitions in the plasticized polymer.

To eliminate the effect of the sample amount, its thickness and surface, the brightness of the light source, etc., the magnitude of the intensity change when determining the degree of completion of the swelling process must be expressed as a dimensionless ratio

/ H- / 0

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where / n is the current value at the moment of the beginning of measurements;

/ o is the amount of dark current arising in the system in the absence of the sample in the light flux; / - current value of current. Example 1. FIG. Figure 2 shows the dependences of the intensity of polarized light passing through the dispersion of a copolymer of nitrile acryl with methyl acrylate in a plasticizer on the time of thermostating at a given temperature. Comparison of the curves shows the possibility of determining the end time of the swelling process, the speed of the process and the degree of its completion, characterized by the intensity value at the end of the swelling process.

Example 2. FIG. 3 shows the change in the intensity of polarized light,

passing through the dispersion of a copolymer of nitril acryl with methyl acrylate when the sample is heated at a certain rate.

A sharp decrease in the intensity of polarized light indicates rapid gelation at temperatures above 45 ° C. The curves show a region of some increase in intensity, preceding the onset of the rapid swelling of the polymer. This effect, as well as the bend on the curve in the temperature range 55-65 ° C, due to the structuring of a part of the polymer, is usually not detected by other methods for studying the process of swelling.

Subject invention

A method for determining the degree of swelling of polymers in plasticizers, by measuring the intensity of light reflected or passing through the sample under investigation, characterized in that, in order to automate and improve the determination accuracy, the test sample is subjected to heating, for example using a heating table, and

The monitoring is carried out using a polarization microscope and a setup for automatically recording the change in the intensity of polarized light.

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