New trends in epr and epr kinetics studies in the stabilization mechanism by N‐oxyl radicals

Faucitano, A.; Buttafava, A.; Mongini, G.; Martinotti, F.; Berzero, A.; Greci, Lucedio; Marin, Alexander; Neri, C.; Farris, R.

doi:10.1002/apmc.1995.052320104

Cited by 4 publications

(13 citation statements)

References 6 publications

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“…45, NO. 2,1998 and mechanism :10,18 initial auto-acceleration followed by auto-deceleration due to gelation, radical trapping, formation of structural heterogeneities and microgels, termination process controlled by reaction di †usion. While cross-linking polymerization proceeds, the physical state of the medium changes from a viscous liquid to a viscoelastic rubber and, in some cases, Ðnally to a glass.…”

Section: Kinetics Of Ultrafast Photopolymerizationmentioning

confidence: 99%

The use of UV irradiation in polymerization

1998

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Section: Kinetics Of Ultrafast Photopolymerizationmentioning

confidence: 99%

The use of UV irradiation in polymerization

1998

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“…All these groups are the products of polypropylene oxidation and, as would be expected from the literature, the concentration of these species increases with irradiation dose. 12,22,23 Figure 3 shows the spectra in the region of 1660 -1800 cm Ϫ1 from nonannealed samples and samples annealed at 147 and 157°C irradiated to doses of 0 and 50 kGy. There is exact superposition of the curves at 0 kGy, indicating that the annealing treatment itself did not introduce any oxidation.…”

Section: Tensile Testingmentioning

confidence: 99%

The morphology of irradiated isotactic polypropylene

Zhang

Cameron

1999

J. Appl. Polym. Sci.

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ABSTRACT:The research in this article explores the response of semicrystalline isotactic polypropylene to gamma radiation in air, and relates the morphological changes of the polymer to corresponding changes in mechanical properties. The effect of the initial morphology of the polymer on its response to irradiation is considered using infrared spectroscopy (FTIR), small-and wide-angle X-ray scattering, dynamic mechanical thermal analysis (DMTA), and mechanical testing. The extent of chain scission and crosslinking is dependent on the dose but not the initial starting morphology. These chemical changes cause the crystallinity to increase slightly, and the glass transition temperature to rise by a few degrees in all samples, but the overall morphology is only subtly changed. In contrast, a major deterioration in mechanical properties is caused. The effects of the irradiation observed under these conditions are similar in each material and the ultimate properties determined by the properties seen in the original material.

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“…The mechanism of photooxidation is crucial for the understanding of natural aging of aliphatic polyamides, and it has been widely studied. − …”

Section: Introductionmentioning

confidence: 99%

“…Remarkable information on the photooxidation of nylon-66 (Ny66) has been provided in the past by investigations that used mainly UV, IR, and wet chemistry methods to follow the process and to identify the products formed. − …”

Section: Introductionmentioning

confidence: 99%

“…The main step in photooxidation of Ny66 is believed to consist in a hydrogen abstraction from the methylene group adjacent to the amide NH, leading then to the formation of a hydroperoxide intermediate, which then decomposes thermally, generating the actual products of Ny66 photooxidation, as shown in Scheme . −

1 Photodecomposition of Nylon-66 Hydroperoxides …”

Section: Introductionmentioning

confidence: 99%

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MALDI Investigation of the Photooxidation of Nylon-66

Carroccio¹,

Puglisi²,

Montaudo

2004

Macromolecules

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Matrix-assisted laser desorption ionization mass spectrometry (MALDI) was used to determine the structure of the molecules produced in the photooxidative degradation of nylon-66 at 60 °C in air. The MALDI spectra of the photooxidized nylon-66 (Ny66) show the presence of nearly 40 compounds, as compared to only four in the original Ny66 sample, and provide information on the structure and end groups of the oligomers produced in the oxidation. The structural analysis of the photooxidized species provided by the MALDI spectra allowed drawing a detailed map of the photodecomposition mechanisms of Ny66. Our results extend the currently accepted picture for the photooxidation mechanisms of Ny66, confirming previous insights into the hydrogen abstraction and subsequent formation of a hydroperoxide intermediate, but also reveal that Norrish I and Norrish II chain cleavage reactions play an important role in the photooxidation process of Ny66. Ny66 films exposed for 12 h show the appearance of only photooxidation products generated by the hydrogen peroxide decomposition, indicating that the chain photocleavage reactions Norrish I and Norrish II type do occur at a later stage of irradiation. An explanation is offered for the appearance of this induction period. It is expected that future MALDI studies may have an impact on the current views on photooxidation processes of other polymer systems.

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New trends in epr and epr kinetics studies in the stabilization mechanism by N‐oxyl radicals

Cited by 4 publications

References 6 publications

The use of UV irradiation in polymerization

The use of UV irradiation in polymerization

The morphology of irradiated isotactic polypropylene

MALDI Investigation of the Photooxidation of Nylon-66

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