CS265342B1 - A way of evaluating the aging of polyesters, especially overweight - Google Patents

Abstract

The solution concerns a method for assessing the aging of polyesters, mainly undrawn polyester fibers and films, the elongation of which during further processing depends on the degree of aging of the polymer. The solution consists in inducing spherulites in the polymer by treating the polymer with chloroform and in measuring the size of the thus induced spherulites using electron microscopic images. The longer the residence time of undrawn polyester fibers between spinning and drawing, the larger the induced spherulites are and thus the elongation is impaired.

Description

The invention relates to a method for assessing the aging of polyesters, in particular non-elongated polyester fibers and films.

In the process of preparing polyester technical fibers by the classical - discontinuous process between spinning and drawing, the fibers remain in the undrawn state for some time due to the technological process, which may affect changes in some structural parameters and thus affect the process of yielding.

The assessment of the impact of residence time between spinning and drawing of these fibers on changes in structural parameters is made using physical methods.

There is no known work in the literature to assess the aging of polyesters, but especially polyester fibers by induced chloroform crystallization.

The principle of evaluating the aging of the polyesters, in particular the polyester fibers and films of the present invention, consists in inducing spherulites in the polymer by treating the polymer with chloroform for at least 5 minutes and measuring the size of the spherulites thus induced by electronomicroscopic images.

The results of physical methods of assessing the influence of the residence time of undrawn fibers between spinning and drawing show small changes in the values of structural parameters (degree of crystallinity, orientation, structural modification, etc.). The advantage of the proposed method of assessing the aging of undrawn fibers lies in recording a significant change in the size of the morphological formations - spherulites, and in explaining the causes of the deteriorated fiber elongation due to aging.

Example 1

Unstretched polyethylene terephthalate fibers, spun at 295 ° C and wound at a speed of 500 m / min. with a logarithmic viscosity of the polymer of 95 ml / g, were stored in air-conditioned conditions at 22 ° C and 65% relative humidity for 30 days.

At certain time intervals, as shown in the table, fiber samples were taken and the size changes of the spherulites were evaluated due to aging. To induce secondary crystallization, samples of undrawn fibers were immersed in chloroform for 5 minutes. The changes in the size of the spherulites with the length of storage of the undrawn fibers and the influence on the elongation are given in the table:

table

Sample number

Shelf life (h)

Size of spherulites d (^ m)

Increment Diligence d (%)

1 1 2.6 - good 2 96 3.7 42 good 3 720 5.0 92 impaired

Evaluation: The elongation of the polyester fibers during the retention time after spinning to hours proceeded without difficulty. After 30 days between spinning and owing, capillaries ruptured mainly at the beginning of owing, and breaks were also noted. This drawback is related to an increase in crystalline groupings in the polymer system between spinning and drawing, which also has the origin of larger dimensions of secondary crystallized spherulites. By the same procedure, the fibers were treated with chloroform for 15 and 20 minutes and the same values were obtained, indicating that the duration of exposure did not affect the size of the spherulites. Only 3 minutes of spherulites were not well developed when chloroform was applied.

Example 2

Commercially produced polyester films having a thickness of 30 µm, 60 µm and 100 µm were used.

The procedure described in Example 1 was used to induce secondary crystallization except that the films were treated with chloroform for 10 minutes.

The changes in the size of the spherulites depending on the thickness of the foils used are given in the table:

table

sample number Foil thickness (/ im) Size of spherulites d (yim) 1 30 5.1 2 60 4.9 3 100 5.2

Evaluation: The size of the spherulites induced by secondary crystallization with chloroform is not dependent on the film thickness.

Claims (1)

Commercially manufactured polyester films having a thickness of 30 µm, 60 and 100 µm were used. To induce secondary crystallization, the procedure described in Example 1 was used, except that the films were treated with chloroform for 10 minutes. Changes in spherulite size depending on the thickness of the film used are given in the table: Table Example 2 Sample number Film thickness Thickness spherulite 1 (yim) 1 30 5.1 2 60 4.9 3 100 5.2 Evaluation: The size of spherulites induced by secondary crystallization of chloroform is dependent on the film thickness. DISCLOSURE OF THE INVENTION A method for assessing the aging of polyesters, in particular non-long-fiber polyester fibers by induced crystallization, characterized in that spherulites are selected in the polymer by the action of chloroform for more than 3 minutes, and their size determined by electron microscopy.