Search results for " photooxidation"
showing 10 items of 11 documents
Home-prepared anatase, rutile, and brookite TiO2 for selective photocatalytic oxidation of 4-methoxybenzyl alcohol in water: reactivity and ATR-FTIR …
2009
5th European Meeting on Solar Chemistry and Photocatalysis -- OCT 04-08, 2008 -- Palermo, ITALY
Selective photooxidation of ortho-substituted benzyl alcohols and the catalytic role of ortho-methoxybenzaldehyde
2016
It has been recently reported by Palmisano et al. (2015) [1] that the oxidation of 2-methoxybenzyl alcohol (2-MBA) to 2-methoxybenzaldehyde (2-MBAD) proceeds in water under near-UV light with an unexpected catalytic effect of 2-MBAD. In order to investigate the catalytic role of aldehyde in photolytic oxidation of ortho-substituted benzyl alcohols (OSBAs), reactivity runs were carried out with 2-methylbenzyl alcohol (2-MeBA), 2-nitrobenzyl alcohol (2-NBA), 2-hydroxybenzyl alcohol (2-HBA) and 2-chlorobenzyl alcohol (2-CIBA) in the absence and in the presence of their corresponding aldehyde. None of those alcohols showed a measurable oxidation rate even in the presence of their aldehydes but …
Photooxidation Behavior of a LDPE/Clay Nanocomposite Monitored through Creep Measurements
2017
Creep behavior of polymer nanocomposites has not been extensively investigated so far, especially when its effects are combined with those due to photooxidation, which are usually studied in completely independent ways. In this work, the photooxidation behavior of a low density polyethylene/organomodified clay nanocomposite system was monitored by measuring the creep curves obtained while subjecting the sample to the combined action of temperature, tensile stress, and UV radiation. The creep curves of the irradiated samples were found to be lower than those of the non-irradiated ones and progressively diverging, because of the formation of branching and cross-linking due to photooxidation. …
Low-density polyethylene/polyamide/clay blend nanocomposites: Effect of morphology of clay on their photooxidation resistance
2017
The photooxidation behaviour of low-density polyethylene (LDPE)/polyamide (PA) blends, containing polyamide 11 (PA11) or polyamide 6 (PA6), has been investigated in the absence and presence of a small amount of commercial organomodified clay (OMMT). The polymer blends LDPE/PA11 and LDPE/PA6 at 75/25 wt./wt.%, with and without OMMT, have been prepared by a two-step procedure: extrusion and sheet formulation. The formulated complex systems have been subjected to accurate morphological analysis in order to evaluate the effect of the OMMT presence on the refinement of the blend morphology. Furthermore, the produced sheets have been subjected to arterial UVB exposure and the variations of the me…
Effect of the orientation on the photooxidation behaviour of polymer films
2016
Abstract The effect of the orientation on the photooxidation of polymers is quite controversial. Both improvement of the photo-resistance along the oriented direction and worsening of the photooxidation kinetic have been reported. In this work the effect of the orientation has been investigated on films of PE, PP and PET with different degree of orientation and crystallinity. The results show that the photo-stability, measured from the decay of the elongation at break curve as a function of the irradiation time, improves in the more oriented direction, but this is more and more relevant with increasing the crystallinity degree. It has been hypothesized that the reinforcing action of the ori…
Photooxidations of Alkenes in Fluorinated Constrained Media: Fluoro-organically Modified NaY as Improved Reactors for Singlet Oxygen “Ene” Reactions
2007
Creating a stationary fluorinated environment inside the zeolite cavity can increase the reactivity observed for intrazeolite photooxidation of alkenes. Exchanging the zeolite with fluorinated organic cations is a much more effective strategy than simply using a fluorinated solvent for slurry irradiations. Use of cations containing C-F bonds is also more efficient than use of deuterated cations for creation of a singlet oxygen friendly environment where the quenching processes are slowed down. Doping the zeolite with fluoro-organic cation 4 resulted in an increase in the singlet oxygen lifetime to 12 micros.
Unexpectedly ambivalent O-2 role in the autocatalytic photooxidation of 2-methoxybenzyl alcohol in water
2015
An unusual autocatalytic photooxidation of 2-methoxybenzyl alcohol has been observed under UV irradiation in aqueous medium. The homogeneous oxidation is catalyzed by the corresponding aldehyde that is also the main oxidation product. The trend of alcohol disappearance rate matches the typical shape of an autocatalytic process, where a crucial and ambivalent role is played by the presence of molecular oxygen. Low oxygen concentrations give rise to a zero-order reaction since the beginning of irradiation, while higher amounts of oxygen reduce the alcohol oxidation rate until the aldehyde reaches a concentration high enough to speed up the alcohol's conversion. Experiments performed by varyin…
Kinetics of 4-Methoxybenzyl Alcohol Oxidation in Aqueous Solution in a Fixed Bed Photocatalytic Reactor
2010
WOS: 000280384800004
IN-LINE MONITORING OF THE PHOTOOXIDATION BEHAVIOUR OF PP/CLAY NANOCOMPOSITES THROUGH CREEP MEASUREMENTS
2016
The photooxidation of polymer systems is usually investigated by monitoring the change of chemical and molecular structure, morphology and macroscopic after a given period of UV exposition. In a previous paper, La Mantia et al. [1] presented a new apparatus that is able to monitor during the accelerated weathering the effect of the photooxidation on a polymer sample subjected not only to temperature, humidity and UV irradiation, but also to a mechanical stress, fully simulating real working conditions for plastic products. In this work, a polypropylene/organomodified clay nanocomposite has been subjects to the same test and the results compared with those obtained for the pure matrix.
Photooxidation behaviour of LDPE/Clay nanocomposite measured through creep curves
2016
The creep response of Polymer systems is typically investigated upon applying different loads, or under different temperature. However, no evidence exist of creep studies under different loads and temperatures and the simultaneos actionof accelerated weathering. In a previous paper La Mantia et al. [1] presented a new equipment that is able to subject polymer samples to creep under different loads, but also monitor the effect of photooxidation due to the temperature, humidity and UV irradiation, thus fully simulating the real operating conditions for polymer-based items. In tihs work a polyethylene/organomodified caly nanocompositehas been subjectedto combined creep-accelerated weathering c…