Photoprotection of Copper-Amine-Treated Pine

Phenolic UV absorbers containing 2-[(2"-benzotriazinyl)-4'-hydroxy-5'-tert-butylphenyl]ethyliso-cyanate (HBTNCO) and isocyanates of monosubstituted polyethylene glycol (350) as PEGNCO, and commercial Tinuvin 1130 (T1130) and Tinuvin precursor (PT1130) were evaluated for protection of copper-amine treated maritime pine against photodiscoloration. Treated wood was irradiated with UV (ultraviolet) light from a pressure mercury lamp of 400 watts for various periods of time. The color change after irradiation was estimated by using the CIELAB system. Grafting of HBTNCO+PEGNCO to wood surfaces using microwaves provided relatively good protection against discoloration

Steady-State and Dynamic Fluorescence Emission from Abies Wood

Steady-state and single-photon timing fluorescence experiments performed on thin sections of Abies wood which have been reduced and non-reduced by sodium borohydride show that wood luminescence is fluorescence and is mainly due to lignin

Valorisation de la bagasse de canne à sucre (chimie, photochimie et élaboration de panneaux et composites)

Une méthode originale de la modification des fibres de bagasse de canne à sucre est présentée. Elle consiste en l'oxydation au periodate de sodium ou au bioxyde de chlore des groupes hydroxyle phénoliques de la lignine pour l'obtention de quinones suivie du greffage en surface de l'alcool furfurylique. Des matériaux originaux, composites (18 % de fibres et 82 % de résine) et panneaux (90 % de fibres et 10 % de résine) avec une résine phénolique ou lignophénolique ont été élaborés. Parallèlement, une étude photochimique sur des fibres de bagasse a éte entreprise. Cette étude s'est poursuivie à un niveau moléculaire sur de la lignine extraite de bagasse ainsi que sur un modèle dibenzodioxocine de lignine, groupement récemment identifié dans les lignines.An original method of modification of sugar cane bagasse fibres is presented. It consists in the oxidation with sodium periodate or with chlore dioxyde of the phenolic hydroxyl groups of the lignin so as to obtain quinones before the grafting of furfuryl alcohol at the surface. Original materials, composites (18 % fibres and 82 % resin) and panels (90 % fibres and 10 % resin) with a phenolic or lignophenolic resin were realized. At the same time, a photochemical study was undertaken on bagasse fibres. This photochemical study was carried out at a molecular level on lignin extracted from some bagasse and on a dibenzodioxocine model of lignin, a group recently identified in lignins.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSAINT DENIS/REUNION-Droit Lettre (974112101) / SudocSudocFranceReunionFRR

The use of alkyl cinnamates as UV screens for preventing the photo-yellowing of lignin-rich pulps

A number of alkyl cinnamates and related compounds have been synthesized. Upon irradiation in solution, some of the materials undergo cis-trans isomerization and a cycloaddition reaction. Application of these compounds to lignin-free paper does not suppress these reactions. The cinnamates were evaluated as UV screens for preventing the photo-yellowing of the lignin-rich paper. None of the compounds proved to be highly effective, and this result is important for a deeper understanding of the role of UV screens for preventing the light brightness reversion of high-yield pulps

Attempts to Photostabilize Paper Made from High-Yield Pulp by Application of UV Screens Containing Groups to Aid their Compatibility with Cellulose and Lignin

2,4-dihydroxybenzophenone (DHB) is known to be a reasonably efficient UV screen for preventing the colour reversion of papers made from high-yield pulps. Attempts have been made to improve the performance of this material by increasing its compatibility with cellulose and by the introduction of cationic groups which will help it to locate in lignin-rich areas. The latter has proved successful and the results show that, on a molar basis for the 2,4-dihydroxybenzophenone nucleus, the efficiency is increased by the introduction of ammonium and thiouronium groups. An interesting finding was that a 2,4-dialkyloxyderivative of benzophenone showed similar protective power to that observed for DHB

Environmentally friendly films based on chitosan and tetrahydrocurcuminoid derivatives exhibiting antibacterial and antioxidative properties

Environmentally friendly films exhibiting both antibacterial and antioxidative properties were elaborated from chitosan and tetrahydrocurcuminoids (THCs). Two tetrahydrocurcuminoids, THC1 (5-hydroxy-1,7-bis(4- hydroxy-3-methoxyphenyl)hept-4-en-3-one) and THC2 (5-hydroxy-1,7-bis(4-hydroxy-3,5-dimethoxyphenyl)hept-4-en-3-one), were incorporated into a chitosan film. THC1 could be prepared from natural curcumin extracted from turmeric roots (Curcuma longa L.). The resulting tetrahydrocurcuminoid-chitosan films exhibited a high free-radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) in methanol, which was due to a progressive release of the THCs into the solvent. The release kinetics was governed both by molecular interactions between chitosan and THCs and probably by electrostatic forces between the ammonium units in chitosan and the aromatic rings in THCs. These interactions were clearly evidenced by the presence of new absorption bands in the visible regions of the electronic absorption spectra of the THCs. The molecular nature of these interactions was shown using glucosamine, the main monomer of chitosan. When associated with THCs, chitosan retained its bioactivity against Listeria innocua; THCs alone were not bioactive enough against listerial strains

Attempts to Photostabilize Paper Made from High-Yield Pulp by Application of UV Screens and Control of PH

Paper made from bleached chemithermomechanical pulp (CTMP) was treated with UV absorbers, e.g. 2,4-dihydroxybenzophenone and a 2-(2-hydroxyphenyl)benzotriazole derivative (Tinuvin 1130) to reduce the tendency of the paper to undergo photoyellowing. Whilst some of the UV absorbers offer some protection, their effect can be enhanced by use in conjunction with a reducing agent (sodium hypophosphite) and by lowering the pH of the paper by application of potassium dihydrogen phosphate. The best effect was obtained by using Tinuvin 1130 in combination with both a reducing agent and potassium dihydrogen phosphate. The use of hindered phenols in both the presence and absence of thiols offered little protection to the paper

Comparative-Study of Stone-Ground Wood Pulp and Native Wood .2.Comparison of the Fluoresence of Stone-Ground Wood Pulp and Native Wood

The fluorescence spectra of paper made from high yield pulp (stone-ground wood pulp (SGWP)) and of thin sections of a softwood (Abies) were recorded and shown to be very similar. The fluorescence from a wood sample, previously reduced with sodium borohydride, shows a biexponential decay, with the magnitude and contribution of the components being dependent on wavelength. From the bleaching kinetics of the chromophores producing the fluorescence, it is concluded that the emission observed for paper made from high yield pulp and for wood originates mainly from lignin and not as previously suggested from cellulose. The steady state and dynamic fluorescence of some lignin model molecules adsorbed on cellulose indicates that the fluorescence of wood, which has been reduced by sodium borohydride, might -originate to some extent from coniferyl alcohol and biphenyl-type structures