Prooxidant activity of phenolic stabilizers in polyolefins during accelerated photooxidation

Publication date: Available online 18 June 2019Source: Polymer Degradation and StabilityAuthor(s): Miroslav Šlouf, Danuše Michálková, Veronika Gajdošová, Jiří Dybal, Jan PilařAbstractPolymer plaques made of high density polyethylene (HDPE) and of two types of cycloolefin copolymer (COC) differing in glass transition temperature, were stabilized with 0.2 or 1.0 wt % of natural (α-tocopherol) or synthetic (Irganox®1010) phenolic stabilizer or hindered amine stabilizer (Tinuvin®770) and aged using accelerated weathering technique (WOM). The efficiency of the phenolic stabilizers was compared among themselves and with well-established Tinuvin®770. Concentration profiles of radicals generated inside polymer plaques during WOM exposure were determined by ESRI, profiles of oxidation products and crystallinity inside the HDPE plaques were determined by IR microspectroscopy, oxidation products in COC copolymers were identified using ATR, the changes of local mechanical properties of the polymer plaques were characterized using microindentation hardness testing, and their morphology was studied by light and/or scanning electron microscopy. All the techniques evidenced high stability of neat COC against photooxidation processes, whereas neat HDPE exhibited fast photooxidation of the surface layers. Tinuvin®770 was found to provide long term protection to both HDPE and COC against photodegradation. In contrast, the same polymers stabilized with the natural phenolic antiox...
Source: Polymer Degradation and Stability - Category: Chemistry Source Type: research