PSI - Issue 20

Petukhova E. S. et al. / Procedia Structural Integrity 20 (2019) 75–80 Petukhova E. S. and Fedorov A. L./ Structural Integrity Procedia 00 (2019) 000 – 000

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Table 2. The research results of mechanical characteristics of stabilized PE 273-83. № Sample σ r , MPa σ y , MPa ε r , %

3

Е, MPa 1108.8

ρ, g/cm 0.9479 0.9456 0.9449 0.9462 0.9470 0.9460 0.9464 0.9462

1 2

273-83

27.1

22.3 22.1

948.5

23.7 * 13.7-27.9

853.8 * 775-984

931.6 * 790-1051

273-83+0.1 wt% CO3

3 4 5 6 7 8

273-83+0.3 wt% CO3 273-83+0.5 wt % СО3 273-83+0.1 wt% CO4 273-83+0.3 wt% CO4 273-83+0.5 wt% CO4 273-83+0.1 wt% Stafen

24.7 28.3 19.4 29.6 27.0

21.9 22.2 21.9 22.0 22.1 22.6

898.7

1016.2 1122.5

1079.8

719.1

796.6 995.4

1001.5

937.2 748.8

1041.4 1110.8

19.6 * 15.1-25.0

9

273-83+0.3 wt% Stafen 273-83+0.5 wt% Stafen

28.4

22.2 22.9

972.8

1057.0

0.9461 0.9466

27.5 * 17.2-28.2

938.8 * 718-974

1118.9 * 729-1128

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σ r – strength at rupture; σ y – yield strength; ε y – elongation at rupture; Е – elastic modulus; ρ – density. * The first row shows the average value of the studied characteristics. The second row shows the interval, in which the characteristics change, if it is significant.

Fig. 2. Samples of the original and stabilized PE 273-83 storing at the open-air testing area for 1 and 3 months.

It is found that the elongation at rupture for the control samples almost does not change over time. However, there is some tendency to a slight decrease of the studied characteristic. The study of the samples exposed to the climatic factors shows a significant decrease of elongation at rupture for the samples containing the stabilizer Stafen after 9 months. After 12 months of exposure, the samples stabilized with CO3 and CO4 retain their properties, composites stabilized with Stafen approach a brittle state. After 18 months, all materials become brittle. It the work of Smirnova and Zhuk (2016) shown that during operation, stabilizing additives are consumed in chemical reactions with free radicals released under the influence of UV radiation. Hence, the working resource of the stabilizers used in this work is sufficient for 1 year of stable work of the products under the given climatic conditions. It should also be taken into account that the industrial grade of polyethylene was used as the polymer matrix. This grade of polyethylene contains a full range of technological additives, the working resource of which is also exhausted after 12 months of exposure. Aging of polymeric materials is accompanied by restructuring of their submolecular structure caused both by the influence of temperature factors and by the destruction processes accompanied by shortening of macromolecular chains. Such processes are described in works of Martínez -Romo et al. (2015) and Tidjani (2000). Figure 4 shows the results of electron microscopic examination of the control samples and the samples exposed to climatic factors for 18 months.