Fizika Nizkikh Temperatur: Volume 45, Number 12 (December 2019), p. 1538-1548    ( to contents , go back )

Low-temperature features of micromechanical properties of polystyrene

H.V. Rusakova1, L.S. Fomenko1, S.V. Lubenets1, and V.D. Natsik1,2

1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauki Ave., Kharkiv 61103, Ukraine
E-mail: rusakova@ilt.kharkov.ua

2V.N. Karazin Kharkiv National University, 4 Svobody Sq., Kharkiv 61022, Ukraine

Received May 21, 2019, published online October 25, 2019

Abstract

The microindentation of thin plates of polystyrene which is an amorphous linear thermoplastic polymer with the glass transition temperature Тg ≈ 373 K was carried out in the temperature range 77–295 К. As the temperature decreased from 295 K to 140 K the microhardness linearly increased approximately by 2 times. The dependence well correlates with the temperature dependence of forced elasticity limit of polystyrene measured by other authors in the uniaxial compression experiments. At the temperatures of T = 77–140 K the local deformation of polystyrene was reversible: during heating to the room temperature the impressions on the sample surface disappeared completely. The partial deformation reversibility was observed at the indentation in the tem-perature range of 140–190 K, but at the indentation temperatures T > 190 К the impressions remained. The effect of reversibility of polystyrene microdeformation in nitrogen at the temperature of 77 K and close to it is connected with the influence of the adsorption-active medium on the forming of crazes (fibrillar-porous nanostructures); their glass transition temperature is tens of degrees below that of bulk polymer.

Key words: microindentation, low temperatures, polystyrene, glassy state, deformation reversibility, crazes.

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