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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1. Introduction The global production and consumption of polymers is constantly growing. Reliability and durability of plastic products are determined by many factors, the combination of which is determined by the features of their application conditions. The most common climatic factors causing the destruction of materials are intense solar radiation, effect of high and low temperatures, as well as temperature drop both during a year and during a day, etc. The studies by Abdelhafidi et al. (2015), Yousif and Haddad (2013) and Andrady et al. (1998) show that one of the most aggressive climatic factors is solar radiation, especially the ultraviolet part of the spectrum. UV radiation destroys interatomic bonds, leads to formation of free radicals, which accelerate the processes of oxidative degradation and reduce all the mechanical characteristics of the polymer material until product failure. One of the most effective ways to protect polymers from UV radiation as shown by Kucuk et al. (2018), Gray (1998), Huang et al. (2016) and Liu C et al. (2018) is to add ultraviolet adsorbents or stabilizers into the material composition. Radiation adsorbents usually include various pigments and some types of technical carbon, which absorb the energy of ultraviolet and visible light in almost the entire frequency range and convert it into relatively harmless radiation. Stabilizers, unlike ultraviolet radiation adsorbents, prevent the destruction of chemical bonds due to the interruption of radical chain reactions that occur under radiation, as well as various oxidants, for example, oxygen as shown by Grassy and Scott (1988). At present, N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS (NIOCH SB RAS) is developing new high-performance stabilizing additives for a wide range of applications. Due to the unique climatic conditions of the territory of the Sakha Republic (Yakutia), characterized by both large temperatures drop and high levels of solar radiation, as pointed for example by Borisov and Gnatiuk (2018), it was proposed to conduct tests of polyethylene composite materials containing different stabilizers under these conditions. 2. Objects and research methods Unpainted polyethylene of grade 273-83 (PJSC Kazanorgsintez) was chosen as the polymer matrix. This grade of polyethylene (PE) is used for the production of molding products, pressure pipes, fittings, and containers with the volume of 10 dm 3 or more. Table 1 presents some PE properties of grade 273-83.

Table 1. Polyethylene properties of grade 273-83 (http://prioritet-kzn.ru/pnd273-83). Characteristics

Value

0.950-0.955 g/cm 3

Density

Yield strength not less than

22.6 MPa 29.4 MPa

Breaking strength (Strength at rupture) Relative elongation at rupture not less than

700 %

From the wide range of various additives produced by NIOCH SB RAS, we chose stabilizers of grades СО 3, СО 4 and Stafen. Figure 1 shows the chemical and structural formulas of these compounds. In contrast to many additives used for polymers, stabilizers developed by NIOCH SB RAS have a unique combination of working properties ( http://web.nioch.nsc.ru/prikladnye-razrabotki-instituta-2/kommercheskie predlozheniya/263-stabilizatory-polimernykh-materialov): • non -toxic (refer to III-IV hazard classes according to GOST 12.1007.76 (State Standard)); • do not change color of polymeric materials; • multifunctional; • almost non - volatile and thermostable at temperatures above 250° С ; • in mixtures with am ino- and sulfur-containing stabilizers, they show synergism, i.e. a significant increase in stabilizing efficiency; • improve strength, bending resistance and durability, resistance of products to mechanical load.