SU928207A1 - Method of measuring temperatures and energies of molecular transition in polymers - Google Patents

Description

(54) METHOD FOR MEASURING TEMPERATURES AND ENERGIES

ACTIVATION OF MOLECULAR TRANSITIONS IN POLYMERAS2

The invention relates to an experimental technique and can be used to study the structure of ultrathin (100 Au less) polymer layers located on various substrates (including metal x), which allows to study the phenomenon of adhesion, the nature of the destruction of adhesive compounds, the effect of the force field of the substrate on the structure of polymers.

A known method for measuring the temperatures and activation energies of molecular transitions in polymers involves measuring the amplitude of oscillations of the free end of a polymer sample made in the form of a rod, when the frequency of the forcing force applied to the other fixed end of the polymer rod changes. The resonance frequency and width of the resonance curve allows us to determine the tangent of the angle of mechanical loss (tgtP). Measuring tg 8 at various temperatures, we obtain the dependence tgiPoT of temperature, according to which the temperatures and activation energies of molecular transitions 1 are determined.

A measurement method is also known. temperatures and energies of activation of molecular transitions, based on the pulsed method of measuring the absorption coefficient of ultrasound, the essence of which is comparing the amplitudes of the pulses that have passed a different acoustic path in the polymer sample and determining the absorption coefficient depending on the temperature. The resulting spectrum is determined, "g

10 temperature and activation energy of a molecular transition 2.

Closest to the present invention is a method for measuring the temperatures and energies of activations of molecular

15 transitions of polymers, including the cooling of the sample to, the region of learning with ionizing radiation — at this temperature, smooth heating — simultaneous registration

20 of the spectrum of radio thermoluminescence (RTL) 3.

The disadvantage of this method is that the limiting thickness of the samples for which registration of the RTL output is possible is 100,000 A. Therefore, this method is unsuitable for studying polymers with a thickness of around 100 A.

The purpose of the invention is to reduce 30 the thickness of the object under study AND;

caMiiiM extension of the circle of objects under study.

The goal is achieved by agreeing ({on the method of measuring the temperatures and activation energies of molecular transitions of polymers, including cooling the sample to -19 bC, irradiating with ionizing radiation at this temperature, smooth heating with simultaneous recording of the radio thermoluminescence spectrum before cooling them to vacuum to a pressure not lower than above mm PI. from., irradiated in vacuum, and the subsequent heating is carried out with a speed of 1.5 - 18 s / min.

The essence of the method is as follows.

Samples are prepared in the form of various effective thicknesses of layers of polyethylene on a substrate by mechanical destruction of adhesive joints obtained in the same contact mode.

Different thickness of the layer is achieved by delamination of these adhesive joints at different temperatures, which ensures the localization of the fracture front at different distances from the interface due to the change in the nature of the distribution of stresses in the adhesive joint.

Samples of metal foil with a layer of polymer in the form of discs are vacuumed at a pressure not exceeding 10 mm Hg Art., cooled to the temperature of liquid nitrogen and irradiated under vacuum in y-quanta of the Co source (dose of 1 .GLrad). Then the samples are placed with a thermal illuminator and, heating at a rate of 1.5 to 18 s / min, the radio thermoluminescence spectrum (RTL) is recorded, noting the temperature position of the relaxation maxima (Tt).

Figure 1 shows the radio thermoluminescence spectra of an ultrathin layer of polyethylene (f 400 A thick) on steel, taken at a heating rate of 10 K / min, subjected to a vacuum before irradiation at a pressure of 10 mm Hg. St,, (curve 1); 10 mmHg Art. (curve 2); 10 mmHg Art. (curve 3); Fig. 2 shows the radiothermoluminescence spectra of a superfine polyethylene layer (400 A thick) on steel, obtained at heating rates: 20 deg / min (curve 4); 18 deg / min (curve 5); 10 deg / min (curve 6); 1.5 degrees / min (curve 7); 1 deg / min (curve 8), vacuuming before irradiation is performed in all cases with P 10

mm Hg Art.

The activation energy of the relaxation transition (Ep) is found in the form of the maximum PTL from the ratio

  CTDD.

gp - -;

t f gpa

where R is a gas constant;

T is the temperature of the high-temperature side of the maximum, where the luminescence intensity falls by half.

The technical and economic effect of the method is to expand. the limits of measurement of the relaxation characteristics of samples with a thickness of 3 °, on the order of magnitude smaller (up to 100 A) than by a known method.

This makes it possible to study the relaxation properties of adhesive compounds in the immediate vicinity of the metal substrate, as well as to more subtly differentiate the measurement of properties in the adhesive layer.

The invention makes it possible to obtain quantitative information on the relaxation and structural characteristics of ultrathin polymer layers on a metal substrate, which, in turn, makes it possible to purposefully influence the process of obtaining adhesive compounds in metal plastics.

Claims (3)

1. Authors certificate of the USSR 282724, cl. C- 01 N 23/00, 1970. 2. Perepechko I., Acoustic Polymer Research Methods. Ni , 5 Himi, 1973, p. 70 3. N. Ya. Buben et al. Investigation of combined systems on the basis of elas, tomers by the method of radio thermoluminescence. - High molecular weight compounds, 1967, t, (A) IX, No. 10, p. 2275.