Assessment of destruction of polyethylene modified with pro-oxidants in the context of environmental safety

Abstract

The paper presents the results of the evaluation of the destruction of polyethylene LDPE (hereinafter-PE), modified by prooxidants based on iron, copper and cobalt carboxylates (in the amount of 1.5 mass. % ) with accelerated thermal and ultraviolet aging for 192 hours. The assessment of degradation in the context of environmental safety included the determination of the degree of compliance of the materials with the requirements of state standard 33747-2016 "Oxo-biodegradable packaging", according to which the criterion of the efficiency of oxobiodestructionpolyolefins may be a decrease in strength and elongation at break of the sample at accelerated aging, as well as the quantitative determination of the release of formaldehyde during thermal degradation modified with prooxidants PE for comparison with the maximum permissible concentration. The rheological parameters of the materials were studied and a comparative assessment of the melt viscosity reduction and reduction with respect to elongation at break in the dynamics of accelerated thermal and UV aging of the PE modified with prooxidants in the selected time interval of 192 hours of exposure was carried out. A decrease in the relative elongation at rupture of PE containing cobalt - based prooxidant by 94% at thermal aging for 192 hours, and by 46% at ultraviolet was established. For PE modified with copper carboxylate, these values were 64 and 33 %, respectively, for PE modified with iron carboxylate – 35% and 40%, respectively. The reduction of strength by 95% of the initial value for 192 hours of temperature exposure was achieved in a sample modified with cobalt, which confirms its compliance with state standard 33747-2016. For other samples, the degree of strength reduction in the selected time interval does not allow to assess compliance with the specified standard. The release of formaldehyde during thermal aging for 192 hours per 1 g of the PE sample modified with cobalt carboxylate was 0.051 mg/m3, for PE modified with copper carboxylate – 0.032 mg/m3, for PE modified with iron carboxylate – 0.034 mg/m3. Installed excessive concentrations of formaldehyde in air hood PH with the carboxylate of cobalt 1.2 times under thermal aging 96 hours and 1.5 times the thermal ageing of a maximum of 192 hours. The reduction of the viscosity of PE containing cobalt – based prooxidant by 90% at thermal aging for 192 hours and by 10% at ultraviolet was recorded. For PE modified with copper carboxylate, these values were 9 and 2 %, respectively, for PE modified with iron carboxylate – 8 and 5%, respectively.