Photooxidative Degradation of Polypropylene

Balaban, L.; Majer, J.; Veselý, Karel

doi:10.1002/polc.5070220242

Cited by 13 publications

(6 citation statements)

References 4 publications

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“…It was found that the steady oxidation rate is proportional to spectral overlap integral (i.e. UV-light intensity) at a power close to 1/2, in close agreement with the usual analytical solution determined from the basic auto-oxidation scheme in the literature [67,69,71]. It can be thus written:…”

supporting

confidence: 61%

A general kinetic model for the photothermal oxidation of polypropylene

François-Heude

Richaud

Desnoux

et al. 2015

Journal of Photochemistry and Photobiology A: Chemistry

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. A B S T R A C TA general kinetic model for the photothermal oxidation of polypropylene has been derived from the basic auto-oxidation mechanistic scheme in which the main sources of radicals are the thermolysis and photolysis of the most unstable species, i.e hydroperoxides. Thermolysis is a uni-or bi-molecular reaction whose rate constant obeys an Arrhenius law. In contrast, photolysis is exclusively a unimolecular reaction and its rate constant is independent of temperature. According to the quantum theory, this latter is proportional to the energy absorbed by photosensitive species and thus, accounts for the impact of UVlight intensity and wavelength on the global oxidation kinetics.The validity of this model has been checked on iPP films homogeneously oxidized in air over a wide range of temperatures and UV-light sources. It gives access to the concentration changes of: (i) primary (hydroperoxides) and secondary (carbonyls) oxidation products, (ii) double bonds, (iii) chain scissions and crosslinking nodes, but also to the subsequent changes in molecular masses. These calculations are in full agreement with the photolysis results reported by Carlsson and Wiles in the 70s [1][2][3]. However, the model seems to be only valid for UV-light energies equivalent to about 10 suns as upper boundary, presumably because of multiphotonic excitations or chromophores photosensitization (i.e. termolecular photo-physical reactions), both enhanced at high irradiances.

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supporting

confidence: 61%

A general kinetic model for the photothermal oxidation of polypropylene

François-Heude

Richaud

Desnoux

et al. 2015

Journal of Photochemistry and Photobiology A: Chemistry

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“…Using a mean squares minimization criterion, the activation energy Ea ind is found to be equal to 27 kJ mol À1 . This activation energy is higher than the value of 15 kJ mol À1 found by Balaban for aPP [9], but in agreement with an estimation of 25e 50 kJ mol À1 [1] made from the data of Mayo [51]. By using equation (6) with the determined activation energy, a kind of master curve can be defined at a given temperature from data obtained at various temperatures.…”

Section: Interpretation According To An Empirical Schwarzschild's Lawmentioning

confidence: 54%

“…However, Philippart [11] also found a dependence of the induction time with the inverse of irradiance for only weakly stabilized PP using filtered medium pressure mercury lamps. The steady-state oxidation rate was found to vary with the square root of the irradiance in agreement with the analytical solution of the basic auto-oxidation scheme [9,12,16] Cumulated exposure energy is usually chosen as the key variable to follow the polymer degradation because it is very convenient for natural weathering where the exposure parameters undergo temporary fluctuations such as daily/seasonal temperature or UV light variations.…”

Section: Introductionmentioning

confidence: 82%

Influence of temperature, UV-light wavelength and intensity on polypropylene photothermal oxidation

François-Heude¹,

Richaud²,

Desnoux³

et al. 2014

Polymer Degradation and Stability

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. a b s t r a c tA criterion based on the energy absorbed by photosensitive species was proposed to describe the contribution of UV-light to the initiation of the polypropylene photothermal oxidation whatever the light source. The calculation of this energy was performed using the widely accepted quantum theory. The criterion was then introduced in two different types of analytical models commonly used to describe the combined effects of UV light and temperature on induction time, namely: the reciprocity law and kinetic model. The limitations of both types of analytical models were then investigated: the latter, derived from a realistic mechanistic scheme, was found to be much more relevant than the former, which is presumably valid in a restricted range of light intensities, essentially due to its empirical origin. Ó

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“…Most of the photoproducts which appear during irradiation, as a consequence of the presence of chromophoric impurities and/or catalytic residues [26], consisting in the formation of hydroperoxy/hydroxyl species and various carbonyl species (carboxylic acid, esters, peresters, lactones in the region 1800-1600 cm -1 ) were identified [1,4,9].…”

Section: Resultsmentioning

confidence: 99%

“…For instance, the photo-oxidative degradation of polyolefin homopolymers has been extensively studied and reported in numerous publications [1][2][3][4][5][6][7][8][9]. In order to extend their lifetime against photo-oxidative degradation, among sterically hindered amine light stabilizers (abbrev.…”

Section: Introductionmentioning

confidence: 99%

Effects of sterically hindered N-alkoxyamines on photooxidative stability of reinforced polypropylene

Enescu

Frache

2012

E-Polymers

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Abstract:In the present paper the influence of Flamestab ® NOR TM 116 (abbrev. FNOR), a sterically hindered N-alkoxyamine stabilizer, on the photo-oxidative stability of calcium carbonate reinforced polypropylene (abbrev. CCPP) used for production of plastic collars has been investigated. The samples, prepared by melt compounding, were exposed to artificial accelerated photo-ageing carried out at λ>300 nm and 45 o C in air. FT-IR and UV-VIS analysis revealed that the deterioration of neat CCPP takes place very rapidly in comparison with the composites containing FNOR. Hydroperoxides and various carbonyl species are formed as the main degradation products during the photo-oxidation process. Moreover, the intensity of the absorption bands grows with increasing of UV exposure time indicating that the material suffers a photo-oxidative degradation process. Indeed, addition of only 0.1 wt.-% FNOR did not significantly modify the length of the induction period of neat CCPP, but a strong efficiency was obtained by increasing the amount of FNOR (0.5 wt.-%) which shows an increase of eight times more as compared with neat CCPP. Therefore, it may be supposed that OIT is linked to the level of concentration of the stabilizer. This remarkable increase in composite stability demonstrated by a lengthening of OIT is typical for sterically hindered N-alkoxyamine stabilizers since they are very efficient at scavenging freeradicals formed as the polymer degrades. In other words, these UV stabilizers are converted to nitroxide radicals (see Scheme 1) which readily trap the polymer degradation species to produce alkoxyamines. Then, the formed alkoxyamines do subsequently react with peroxy radicals to regenerate the active nitroxide radical, thereby this process (called Denisov cycle) proceed in a regenerative cycle, thus retarding oxidative polymer degradation. The increase of absorbance in the carbonyl region as a function of irradiation time was used to determinate the photooxidation rate. It was found out that the photooxidation rate measured from the slope of linear part of the curves is significantly decreased for the CCPP/FNOR0.5 composite compared to neat CCPP. In the light of the above mentioned findings, FNOR could be taken into consideration as an UV stabilizer for CCPP.

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Photooxidative Degradation of Polypropylene

Cited by 13 publications

References 4 publications

A general kinetic model for the photothermal oxidation of polypropylene

A general kinetic model for the photothermal oxidation of polypropylene

Influence of temperature, UV-light wavelength and intensity on polypropylene photothermal oxidation

Effects of sterically hindered N-alkoxyamines on photooxidative stability of reinforced polypropylene

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