STABILIZATION OF POLYETHYLENE AND OTHER POLYOLEFINS BY PHENOTHIAZINE DERIVATIVES

This paper presents the results of the synthesis and study of the thermostabilizing properties of a number of new derivatives, as well as previously known derivatives of Phenothiazine (PT). The objects of the study were: cis-10-propenylphenothiazine (cis-10-PPT), 1-ethyl-2-methyl-3-(10H-phenothiazin-10-yl)-2,3-dihydro-1H-pyrido[3,2,1-kl]phenothiazine. Propenylphenothiazine dimer (DPРT),1-ethyl-2-methyl-3-(5-oxido-10H-phenothiazin-10-yl)-2,3-dihydro-1H-pyrido[3,2,1-kl]phenothiazine 7-oxide. S-oxide (DPРTО),1-ethyl-2-methyl-1H-pyrido-[3,2,1-k,l]phenothiazine. Pyridophenothiazine (PyrPT) and a mixture of two fractions of 10-propenylphenothiazine oligomers: 1-ethyl-2-methyl-3-(10H-phenothiazin-3-yl)-2,3-dihydro-1H-pyrido[3,2,1-kl]phenothiazine (ОPРT 1) and 3,7-bis(1-ethyl-2-methyl-2,3-dihydro-1H-pyrido[3,2,1-kl]phenothiazin-3-yl)-10H-phenothiazine (ОPРT 2).  A well-known industrial stabilizer, Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1010), was used as a comparison sample. Irganox 1010 is an antioxidant based on spatially hindered phenol with a high molecular weight, has very low volatility, is used as an antioxidant and heat stabilizer for polypropylene, polyethylene, impact-resistant polystyrene, poly-4-methyl-pentene. To evaluate the stabilizing effect of PT derivatives, a powder of unstabilized templene (a copolymer of poly-4-methylpentene-1 and n-hexene) was used. Thermogravimetric (TGA) and differential thermal analysis (DTA) methods were used to study the thermal oxidative degradation of polymer compositions based on templene in open and closed crucibles. For each tested stabilizer sample, the following were determined: the temperature of the beginning of decomposition of the polymer composition (Tb.d., °C), the decomposition temperature of 1% of the mass of the tested polymer composition (T1%, °C). Based on the experimental data obtained, the following were calculated: the thermal stability of the tested compositions, the effective activation energy (Ea). The thermostabilizing effect of additives in compositions based on ethylene copolymer with vinyl acetate (savylene), high-pressure polyethylene (HDPE) was evaluated according to TU 301-05-91, according to the accumulation time of acidic polymer degradation products in them during aging at 180 °C and 160 °C in oxygen current (pH), as well as by the change in the melt flow index in the process of holding the polymer in air at 200 °C for two hours (for savylene and HDPE). In addition, the effectiveness of the additives was evaluated by changing the mechanical properties of the compositions: tensile yield strength (σt), elongation (ε, %). It was found that mixture of two fractions oligomers (OPPT 1) and (OPPT 2) products synthesized from cis-10-PPT have a sufficiently high stabilizing effect. For citation: Zhuravkov S.P., Boytsova E.L., Slavinskaya A.V. Stabilization of polyethylene and other polyolefins by phenothiazine derivatives. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 12. P. 96-101. DOI: 10.6060/ivkkt.20246712.6941.