Bernard De Jeso

Penetration of amino-silicone micro- and macro-emulsions into Scots pine sapwood and the effect on water-related properties

Abstract An amino-silicone in the form of a micro- and a macro-emulsion (average particle size 40 and 120 nm, respectively) was tested in impregnation of solid wood. During vacuum-pressure impregnation, the uptake of 5% emulsions was only slightly reduced compared to water up-take. At 15% concentration, a significant reduction in emulsion uptake was observed, particularly in the radial and tangential directions of the wood. The penetration of silicone into the cell wall was dependent on the particle size of the emulsion. Applied as a macro-emulsion, a maximum of only 14% of the total silicone penetrated the cell wall, whereas 25–35% of the silicone was found in the cell wall when applied as a micro-emulsion. The degree of cell wall penetration of silicone for the micro-emulsion was confirmed by X-ray micro-analysis (SEM-EDX). The penetrated silicone caused bulking and dimensional stability. 1H NMR relaxometry T 2 distributions were determined for dried and moisture-conditioned wood samples. The silicone-treated specimens displayed spin-spin interactions of protons from water and silicones (or their emulsifiers). Conditioning of samples at 25°C and 65% relative humidity appeared to cause a decrease in the mobility of the non-water protons of the silicone and/or emulsifier. Freezing to -5°C caused separation of protons from bound water and from the silicone at low relaxation times. It is assumed that treatment with the micro-emulsion reduced water sorption due to micro-pore blocking in the cell wall. The formation of a sandwich complex is postulated, which comprises cell wall polymers, water molecules and a layer of silicone.

Moisture content and extractive materials in maritime pine wood by low field 1H NMR

Summary The low field 1H NMR relaxometry technique has been shown to be effective in determining the qualitative and quantitative moisture content and the water state distribution in maritime pine wood (Pinus pinaster Ait). Further investigations on extractive materials in resin-rich samples evinced the presence of oleoresin components, which may disturb adhesion on pine wood boards.

Chemical reaction of maritime pine sapwood (Pinus pinaster Soland) with alkoxysilane molecules: A study of chemical pathways

Abstract The chemical modification of maritime pine sapwood (Pinus pinaster) with alkoxysilanes was studied according to three different pathways: carbamoylation with 3-isocyanatopropyltriethoxysilane, etherification with 3-glycidoxypropyltrimethoxysilane and alcoholysis of n-propyltrimethoxysilane. Grafting was confirmed by weight percent gain calculations (WPG), infrared spectroscopy (FTIR) as well as 13C and 29Si NMR CP MAS analysis. Signals of the grafted groups in the different spectra were assigned and the reactivity of the trialkoxysilane moieties towards wood was discussed. Experiments with model wood blocks showed that the reactions investigated occurred within the wood cell walls. Grafted chemicals were found to be relatively stable with regard to water leaching but only slight dimensional stabilisation was noted after treatment.

Enzymes in organic synthesis VII: enzymatic acylation of amines

Abstract Lipases and esterases catalyze amide synthesis from primary amines in the presence of various esters. Lipase SP 382 exhibited a very high activity and specificity.

The dimensional stabilisation of Maritime pine sapwood (Pinus pinaster) by chemical reaction with organosilicon compounds

Summary The dimensional stabilisation imparted to Maritime pine sapwood by chemical modification with hydrophobic organosilicon compounds was investigated. Modification was performed via esterification, using different chemically synthesised models bearing trimethylsilyl groups: 3-trimethylsilylpropanoic anhydride (I), 2-trimethylsilylmethylglutaric anhydride (II) and trimethylsilylethenone (III). Grafting was confirmed by infrared spectroscopy as well as 13C and 29Si NMR CP MAS analysis and was located into the wood cell walls. The dimensional stabilisation induced by I and II appeared to be stable during three oven-dry/water-soak cycles and, for a given number of hydroxyl blocked, to be superior to that imparted by acetylation. The graft from III, however, was found to hydrolyse progressively into an acetyl group via a metallotropic rearrangement. Further investigation on the hygroscopicity and swelling behaviour of modified wood from I and II indicated that dimensional stabilisation was attributable to a bulking effect rather than a change in substrate hygroscopicity. The bulky grafts from I and II were, in particular, thought to locally over-swell the wood cell wall, revealing regions with new water-accessible hydroxyl groups.

Enzymes in organic synthesis. VI: Scope and enantioselectivity of enzymatic hydrolyses of organosilyl-substituted esters

Abstract Enzymatic hydrolysis of the title esters by esterase or lipase gave the corresponding acid or alcohol. In some cases, a high enantioselectivity was observed.

Imines et enamines stanniques: preparation et caracterisation

Abstract The organotin derivatives corresponding to the equilibrium imine—enamine have been obtained by two different routes: ( 1 ) reaction of organotin enolates with stannazane; ( 2 ) reaction of tributyltin chloride with a magnesium derivative of imine. The first method allows the preparation of the less hindered compounds, the reverse being true for the latter. Their characterisation by various physical methods (IR, 1 H and 119 Sn NMR) shows the existence of two metallotropic forms ( N - and C -derivatives).

Functionalisation of wood by reaction with 3-isocyanatopropyltriethoxysilane: Grafting and hydrolysis of the triethoxysilane end groups

Abstract The chemical modification of maritime pine sapwood (Pinus pinaster Soland) with 3-isocyanatopropyltriethoxysilane (IPTES) and its subsequent hydrolysis were investigated. The formation of urethane linkages after the carbamoylation reaction was confirmed by Fourier-transform infrared (FTIR) spectroscopy. The weight percent gain (WPG) obtained was found to be commensurate with the quantity of IPTES in the reagent solution. Swelling measurements combined with scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis showed that the reaction occurred within the wood cell walls. Hydrolysis of the grafted triethoxysilane ends in highly carbamoylated wood was also envisaged: the modifications generated after prolonged contact with water were studied by FTIR spectroscopy and 13C and 29Si nuclear magnetic resonance cross-polarisation with magic-angle spinning (NMR CP MAS) analysis. The chemical environments found for silicon (Si–OH, Si–OEt or Si–OSi) before and after hydrolysis were thus identified and a schematic representation of the silicon structures most often encountered in modified wood was proposed.

Time-domain 1H NMR characterization of the liquid phase in greenwood

Abstract The time domain of 1H NMR spectroscopy allows straightforward editing of the T 2 relaxation profiles in maritime pine wood. A new method from the Carr-Purcell-Meiboom-Gill sequence is proposed to measure the amount and distribution of water in wood, as well as the location of major dissolved organic materials. A general calibration model giving reliable and precise identification of these parameters is described. The method presented for editing T 2 relaxation profiles (obtained by the Contin program) may be helpful in solving practical drying and gluing problems in the wood industry. It can be used for monitoring chemical modifications of wood fibers involved in the design of wood composite materials.

Imines et enamines stanniques : IV. Protolyse: synthese d'enamines secondaires; structure, isomerisation, reactivite vis a vis de l'acrylonitrile☆

Abstract The partial protolysis of organotin imines—enamines leads to organic secondary enamines, which we found to be stable in completely aprotic media. Their structure was determined by IR and NMR methods, and their reactivity towards acrylonitrile studied. The results show a much greater reactivity for enamines, as compared to that of the corresponding imine tautomers.