The origins of volatile oxidation products in the thermal degradation of polypropylene, identified by selective isotopic labeling

Real-time quantitative analysis of volatile products generated during solid-state polypropylene thermal oxidation

“…It is thus possible to differentiate two compounds of the same nominal molecular mass, but with different exact masses (Table 1). For instance, the peak here observed at 72 g/mol must be assigned to acrylic acid instead of butanone [4,7] or 2methyl-2-propen-1-ol [6,8] as previously reported in the literature. For sake of simplicity, six main VOCs, each representing more than 5 mol% of the total amount of VOCs, are considered in this study (Table 1).…”

“…Identification and quantification of VOCs brought valuable information about the prevailing mechanisms of polypropylene oxidation, consistent with their precursory macromolecular oxidation products [1,[3][4][5]7,16,17]. VOCs analysis was particularly applied to the determination of the relative sensitivities to oxidation of methyne and methylene -besides methyl-units to oxidation [8]. It was confirmed that methyne units are about 10 times more reactive than the methylene ones, as in previous results obtained on macromolecular oxidation products by derivatization methods [18] or isotope labeling [17].…”

“…The "zip" mechanism proposed by Delprat [2] allows explanation of the high amounts of acetone rather than further reactions undergone by methyl ketones. However, according to Bernstein et al [8], the radical attack in g position of a methyl ketone would explain the generation of 2,4 pentanedione. Formaldehyde generation is reported according to the mechanism of Hoff and Jacobsson, which consists of the oxidation of primary alkyl radicals [11,12].…”

“…Analysis of Volatile Organic Compounds (VOCs) emitted during degradation of polypropylene (PP) has been widely studied during the last three decades under various exposure conditions such as photo-oxidation [1][2][3], radiooxidation [4][5][6] and thermal oxidation in both solid and molten states [7][8][9][10][11][12][13][14]. Many VOCs were identified, particularly in thermal oxidation by Hoff et al [15] or more recently by Bernstein et al [8]. Moreover, except for a recurrent group of VOCs, multiple products were identified by the different authors even for similar ageing conditions, possibly due to:…”

Identification of volatile butyl rubber thermal-oxidative degradation products by cryofocusing gas chromatography/mass spectrometry (cryo-GC/MS).

“…In the future, the headspace above these materials will be sampled; the degradation species will be characterized; and comparisons will be drawn to samples presented in this manuscript. In addition, these results and those for other polymers can be compared to compounds of interest to the DOE complex that have already been studied by this group: polyethylene [18,19], polypropylene [20][21][22], nylon 6.6 [23][24][25][26], and poly(ethylene-co-vinyl acetate). This information may identify common degradation products and therefore degradation pathways amongst WR materials.…”