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Insights into oxidation mechanisms in gamma-irradiated polypropylene, utilizing selective isotopic labeling with analysis by GC/MS, NMR and FTIR

Bernstein, Robert and Thornberg, Steven M. and Assink, Roger A. and Mowery, Daniel M. and Alam, M. Kathleen and Irwin, Adriane N. and Hochrein, James M. and Derzon, Dora K. and Klamo, Sara B. and Clough, Roger L. (2007) Insights into oxidation mechanisms in gamma-irradiated polypropylene, utilizing selective isotopic labeling with analysis by GC/MS, NMR and FTIR. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 265 (1). pp. 8-17. ISSN 0168-583X. https://resolver.caltech.edu/CaltechAUTHORS:20170408-162439445

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Abstract

In an effort to shed additional light on the chemical mechanisms underlying the radiation–oxidation of polypropylene (PP), we are using samples having selective ^(13)C isotopic labeling at the three unique sites within the macromolecular structure. After radiation exposure, we applied GC/MS, solid-state ^(13)C NMR, and FTIR to evaluate the applicability of each technique in identifying the molecular labeling of the oxidation products, with the goal of determining the site of origin of the products with respect to the macromolecule. Using GC/MS, we have identified the position of origin of CO_2 and CO from the polymer. Most of the CO_2 (60%) and CO (>90%) come from the C(1) (methylene) position of PP, with (30%) of the CO_2 originating from the C(3) (methyl) position, and 10% coming from the C(2) (tertiary) position. By GC/MS we have also identified the labeling patterns in four volatile oxidation products (acetone, methylisobutylketone, isobutane, and methyl acetate), and have used this information to map each compound onto the macromolecular framework. Using NMR we have quantified the time-dependent formation of solid-phase degradation products occurring from post-irradiation aging of PP samples held for 28 months at room temperature in air. Most of the solid oxidation products occur at the C(2) (tertiary) site; the predominant species, C(2) peroxides, increase linearly during the first 2 years, after which they plateau at a relatively high concentration.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.nimb.2007.08.100DOIArticle
Additional Information:© 2007 Elsevier. Available online 25 September 2007.
Subject Keywords:Polymer irradiation; Polymer oxidation; Polymer degradation; Polypropylene; Isotopic labeling; Volatile degradation products; C-13 labeling; C-13 NMR
Issue or Number:1
Classification Code:PACS 61.82.Pv
Record Number:CaltechAUTHORS:20170408-162439445
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170408-162439445
Official Citation:Robert Bernstein, Steven M. Thornberg, Roger A. Assink, Daniel M. Mowery, M. Kathleen Alam, Adriane N. Irwin, James M. Hochrein, Dora K. Derzon, Sara B. Klamo, Roger L. Clough, Insights into oxidation mechanisms in gamma-irradiated polypropylene, utilizing selective isotopic labeling with analysis by GC/MS, NMR and FTIR, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 265, Issue 1, 2007, Pages 8-17, ISSN 0168-583X, http://dx.doi.org/10.1016/j.nimb.2007.08.100. (http://www.sciencedirect.com/science/article/pii/S0168583X07013869)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76179
Collection:CaltechAUTHORS
Deposited By: 1Science Import
Deposited On:27 Jul 2017 00:18
Last Modified:03 Oct 2019 16:58

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