Polymer Aging, Stabilizers and Amphiphilic Block Copolymers

0435836 - ÚMCH 2015 RIV US eng M - Monography Chapter
Pilař, Jan - Pospíšil, Jan
Hindered amine stabilizers as sources of markers of the heterogeneous photooxidation/photostabilization of carbon chain polymers.
Polymer Aging, Stabilizers and Amphiphilic Block Copolymers. Hauppauge: Nova Science Publishers, 2011 - (Segewicz, L.; Petrowsky, M.), s. 343-357. ISBN 978-1-60692-928-5
Institutional research plan: CEZ:AV0Z40500505
Keywords : polymer photodegradation * polymer photostabilization * hindered amine stabilizers
Subject RIV: CD - Macromolecular Chemistry

Application of Hindered Amine Stabilizers (HAS) is the state-of-the-art approach to protection of carbon-chain polymers such as polyolefins and polystyrene or blends containing these against weathering. During outdoor exposure, the polymers loose their material properties due to solar radiation-triggered photooxidation. The complex mechanism of the stabilization involving cyclic oxidation-triggered transformation of HAS is outlined. Monitoring of the formation of the HAS-developed key transformation products, HAS-related nitroxides, responsible within the regenerative mechanism for the effective stabilization was used to confirm the heterogeneous character of photooxidation of two carbon-chain polymers, polypropylene and a specific polyethylene copolymer. Depth profiles of nitroxides were monitored in a long-term photooxidation regime using Electron Spin Resonance Imaging (ESRI) technique. The shape of concentration profiles of the nitroxides accumulated in the equilibrium state upon filtered Xenon lamp-equipped Weather-Ometer exposure was interpreted in terms of the oxygen diffusion limited oxidation and radiation penetration in oxidation-stressed polymer surfaces. The data indicate differences in the character of the heterogeneous process in dependence on the polymer matrix and on the used stabilizer system based on secondary HAS and O-alkylhydroxylamine HAS and/or HAS combination with UV absorbers. Imaging of nitroxides is a precise tool for marking heterogeneous oxidation of polyolefins.
Permanent Link: http://hdl.handle.net/11104/0240167