Solid-state 13C NMR investigation of the oxidative degradation of selectively labeled polypropylene by thermal aging and y-irradiation.

Journal Article · Wed Dec 01 04:00:00 EST 2004 · Proposed for publication in Macromolecules.

OSTI ID:952112

Mowery, Daniel Michael; Assink, Roger Alan; Klamo, Sara B ^[1]; Clough, Roger Lee; Bernstein, Robert; Derzon, Dora Kay

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1. California Institute of Technology, Pasadena, CA

Unstabilized polypropylene (PP) films having selective {sup 13}C isotopic labeling were subjected to thermal aging at 50, 80, and 109 C and to {gamma}-irradiation at 24 and 80 C. The oxidized films were examined using solid-state {sup 13}C nuclear magnetic resonance (NMR) spectroscopy. Dramatic differences were found in the type and distribution of oxidation products originating from the three carbon atom sites within the PP macromolecule (tertiary carbon, secondary carbon, and methyl side group). Most of the oxidation products that formed on the polymer chain originated through chemical reactions at the PP tertiary carbons. Under all of the aging conditions examined, tertiary peroxides (from the PP tertiary site) were the most abundant functional group produced. Also originating from the PP tertiary carbon were significant amounts of tertiary alcohols, together with several more minor products that included 'chain-end' methyl ketones. No significant amount of peroxides or alcohols associated with the PP secondary carbon sites was detected. A substantial yield of carboxylate groups was identified (acids, esters, etc.). The majority of these originated from the PP secondary carbon site, from which other minor products also formed, including in-chain ketones. We found no measurable yield of oxidation products originating from reaction at the PP methyl group. Remarkably similar distributions of the major oxidation products were obtained for thermal aging at different temperatures, whereas the product distributions obtained for irradiation at the different temperatures exhibited significant differences. Time-dependent concentration plots have been obtained, which show the amounts of the various oxidation products originating at the different PP sites, as a function of the extent of material oxidation.

• Research Organization: Sandia National Laboratories
• Sponsoring Organization: USDOE
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 952112
• Report Number(s): SAND2004-6663J
• Journal Information: Proposed for publication in Macromolecules., Journal Name: Proposed for publication in Macromolecules.
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
AGING
BY-PRODUCTS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
GAMMA RADIATION
NUCLEAR MAGNETIC RESONANCE
OXIDATION
POLYPROPYLENE