Photooxidation mechanism of aliphatic crosslinked polyesters used for flat steel coating

Delorme, Pierre; Lemaire, Jácques; Carrara, Francçoise; Bonnebat, C.

doi:10.1063/1.49436

Cited by 4 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A free-radical chain reaction mechanism has been proposed for photodegradation of polyurethane coatings. 18 A linear correlation between -∆S from DBES and free-radical concentration from ESR for the UVA-340 sample series was reported in our previous paper. 2 ESR signals of the UVB-313 irradiated samples immediately after irradiation durations from 100 to 800 h were also recorded.…”

Section: Esr Resultssupporting

confidence: 57%

“…But an increase of T g and cross-link density of polyurethane after UV irradiation from dynamic mechanical thermal analysis (DMTA) was reported, which suggests a reduction in free volume. 18 The characterization of hole volume from the DBES results provides further evidence. It is believed that the recombination of radicals in the termination steps introduces extensive cross-linking reactions, which becomes the dominant effect leading to structural changes.…”

Section: Dbes Results Of Uvb-313 Irradiationmentioning

confidence: 77%

“…A photooxidation mechanism for polyurethane degradation has been proposed from FTIR studies. 18 Free radicals initiated by the absorption of UV light react with O 2 , forming peroxy radicals (POO • ), which lead to very reactive oxy radicals (PO • ) and then readily undergo chain scission. Chain scission could occur as a main chain scission or a cross-link scission.…”

Section: Dbes Results Of Uvb-313 Irradiationmentioning

confidence: 99%

“…Chain scission could occur as a main chain scission or a cross-link scission. 18 The urethane cross-link (-CH 2 -NH-CO-OR-) reacts with O 2 , losing the hydrogen atom bonded to the carbon atom located in the R-position of the NH group and produces an oxy radical -CHO ˙-NH-COOR-. This alkoxy radical leads to the scission of the cross-link and forms an acid (-COOH) and a primary urethane group (NH 2 COOR-).…”

Section: Dbes Results Of Uvb-313 Irradiationmentioning

confidence: 99%

“…The S parameter decrease after UV irradiation can be interpreted as being due to an overall decrease of free volumes and holes. A photooxidation mechanism for polyurethane degradation has been proposed from FTIR studies . Free radicals initiated by the absorption of UV light react with O 2 , forming peroxy radicals (POO • ), which lead to very reactive oxy radicals (PO • ) and then readily undergo chain scission.…”

Section: Resultsmentioning

confidence: 99%

See 4 more Smart Citations

Degradation of Polymer Coating Systems Studied by Positron Annihilation Spectroscopy. 3. Wavelength Dependence of UV Irradiation Effect

Cao¹,

Yuan²,

Zhang³

et al. 1999

Macromolecules

View full text Add to dashboard Cite

Photodegradation of a polyurethane coating induced by accelerated UV irradiation is studied using three different light sources: 340 nm UVA, 313 nm UVB, and Xe lamps. Doppler-broadened energy spectra (DBES) and positron annihilation lifetime (PAL) are measured as a function of incident positron energy (0-30 keV) and of irradiation time (0-800 h). The photodegradation of the coating is characterized in terms of subnanometer defect changes. Significant variations of S parameter, orthopositronium lifetime, intensity, and lifetime distribution are observed as a function of depth and of exposure time. These results indicate a decrease of free volume and holes at the atomic level during the degradation process. The UV irradiation at 313 nm shows a significant effect compared with that at 340 nm on the photodegradation:(1) the magnitude of S reduction increases a factor of 2 near the surface; (2) the photodegradation rate increases ∼25 times near the surface; (3) the irradiation effect attenuates with depth, and a larger extinction coefficient is observed with shorter wavelength UV irradiation. The observed effect by Xe light irradiation is the strongest among these three light sources. Enhanced degradation at shorter wavelengths is also indicated by increased free radical production, as observed by electron spin resonance spectroscopy.

show abstract

Section: Esr Resultssupporting

confidence: 57%

Section: Dbes Results Of Uvb-313 Irradiationmentioning

confidence: 77%

Section: Dbes Results Of Uvb-313 Irradiationmentioning

confidence: 99%

Section: Dbes Results Of Uvb-313 Irradiationmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 3 more Smart Citations

Degradation of Polymer Coating Systems Studied by Positron Annihilation Spectroscopy. 3. Wavelength Dependence of UV Irradiation Effect

Cao¹,

Yuan²,

Zhang³

et al. 1999

Macromolecules

View full text Add to dashboard Cite

show abstract

A study of the effects of postcure treatments on polyester–melamine coating matrices

Gamage¹,

Hill²,

Pomery³

et al. 2006

Polymer Engineering & Sci

View full text Add to dashboard Cite

The effect of postcure high energy (␥), ultraviolet (UV) and thermal treatment on the properties of polyestermelamine clearcoats of a range of compositions has been investigated. Two initial cure conditions were used, of which one was "optimally" cured and the other undercured. It was found that postcure treatments, particularly ␥ and UV, led to coatings of similar mechanical and thermal properties irrespective of initial cure, although the change in properties on postcure treatment was greater for the under-cured samples. The results were interpreted in terms of the effect of the treatments on the structure of the crosslinked matrices. The study suggests the possibility of the development of a dual-cure process for polyester-melamines, whereby cure optimization and property improvement can be achieved. This could also be used to "correct" for small variations in thermal cure levels brought about by adventitious online fluctuations in cure oven conditions. POLYM. ENG. SCI., 46:532-539, 2006. FIG. 2. Effect of posttreatments (⅐ ⅐ ⅐ ⅐, untreated; ---, 15 kGy ␥; ---8 h UV) on thermal decomposition (DTGA) of thermally undercured samples (cure condition D) with different HMMM concentrations.

show abstract

Going Green: making reality match ambition for sustainable coil coatings

et al. 2016

View full text Add to dashboard Cite

Photooxidation mechanism of aliphatic crosslinked polyesters used for flat steel coating

Cited by 4 publications

References 0 publications

Degradation of Polymer Coating Systems Studied by Positron Annihilation Spectroscopy. 3. Wavelength Dependence of UV Irradiation Effect

Degradation of Polymer Coating Systems Studied by Positron Annihilation Spectroscopy. 3. Wavelength Dependence of UV Irradiation Effect

A study of the effects of postcure treatments on polyester–melamine coating matrices

Going Green: making reality match ambition for sustainable coil coatings

Contact Info

Product

Resources

About