Stéphane Grelier

From Lignin‐derived Aromatic Compounds to Novel Biobased Polymers

Nowadays, the synthesis of (semi)aromatic polymers from lignin derivatives is of major interest, as aromatic compounds are key intermediates in the manufacture of polymers and lignin is the main source of aromatic biobased substrates. Phenols with a variety of chemical structures can be obtained from lignin deconstruction; among them, vanillin and ferulic acid are the main ones. Depending on the phenol substrates, different chemical modifications and polymerization pathways are developed, leading to (semi)aromatic polymers covering a wide range of thermomechanical properties. This review discusses the synthesis and properties of thermosets (vinyl ester resins, cyanate ester, epoxy, and benzoxazine resins) and thermoplastic polymers (polyesters, polyanhydrides, Schiff base polymers, polyacetals, polyoxalates, polycarbonates, acrylate polymers) prepared from vanillin, ferulic acid, guaiacol, syringaldehyde, or 4-hydroxybenzoic acid.

Peroxyformic Acid Pulping of Eucalyptus Grandis Wood Chips and Sugar Cane Bagasse in one Stage and Characterization of the Isolated Lignins

Abstract An improvement in the peroxyformic acid process for the production of chemical pulps from Eucalyptus grandis wood chips and sugar cane bagasse is described. The pulping of these lignocellulosics was carried out in a single stage at 75°C (3 h) in order to benefit from the action of the peroxyformic acid and a subsequent formic acid reflux (110°C, 2 h), using the same liquor. Efficient distillation of the spent liquor allowed recovery of a large quantity of formic acid and phenolic lignin, the latter obtained after mild saponification, followed by precipitation in acidic media. The pulping process was completed with a 0.25M NaOH extraction of the pulp at 60°C to dissolve more lignin. Good quality unbleached pulps were obtained. Kappa numbers (KN) of 14 and 13, and intrinsic viscosities [n] of 1130 and 980 dm3. Kg−2 were obtained, respectively, for E. grandis and sugar cane bagasse. The structures of the lignin fractions were studied by size exclusion chromatography; methoxyl content analysis; eleme...

Comparative study of stone-ground wood pulp and native wood 2. Comparison of the fluorescence of stone-ground wood pulp and native wood

Abstract 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.

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.

Renewable (semi)aromatic polyesters from symmetrical vanillin-based dimers

Two symmetrical biphenyl monomers derived from vanillin, a methylated divanillyl diol and a methylated dimethylvanillate dimer, were synthesized and employed as (co)monomers for the design of renewable (semi)aromatic polyesters. The reactivity in polytransesterification of these new monomers was investigated in bulk in the presence of various catalysts. The polytransesterification between methylated divanillyl diol and a series of bio-based diesters having different chemical structures led to amorphous thermoplastic polyesters with glass transition temperatures ranging from −5 to 139 °C and thermal stability up to 350 °C.

Photochemical bleaching of chemical pulps catalyzed by titanium dioxide

A two-stage process for photochemical bleaching of cellulosic pulps is presented. The first, based on the generation of oxygen active species by the photocatalytic action of TiOZ, and the second on the photochemical decomposition of hydrogen peroxide. Both stages are carried out under alkaline pH and at 85°C in aqueous suspension at a consistency of 5% The experiments were performed on kraft (Eucul~prus grandis, firms pinasfer and Pica muuiana), acesolv (E. grandis) and peroxyformic acid (E. grandis) pulps. The presence of TiO, as photocatalyst showed several advantages, such as reduction of reaction time, preservation of the pulp viscosity, increase of the selectivity during the photobleaching and decrease of the consumption of the bleaching chemicals. UV/Vis and FHR spectroscopies indicate a decrease of the coniferaldehyde structures during the TiO, photocatalyzed stage, whereas quinones entities were found to remain in the residual lignin even

Physical properties and termite durability of maritime pine Pinus pinaster Ait., heat-treated under vacuum pressure

An original heat treatment performed under vacuum pressure was investigated. Maritime pine samples were treated at six different temperatures: 140, 160, 180, 200, 230 and 260°C. The physical and mechanical consequences, i.e. bending strength (MOR), modulus of elasticity (MOE), hygroscopic behaviour, equilibrium moisture contents and anti-swelling efficiency (ASE) were studied. A no-choice feeding test according to the NF EN 117 standard was achieved. Temperatures up to 200°C had no significant effect on wood properties. However, at 230 and 260°C, the decrease in MOR was severe, reaching 42.5 and 62.5%, respectively. Whatever the treatment conditions, wood samples were still highly degraded by termites, revealing no increase in their durability.

Modification of Fagus sylvatica L. with 1,3-dimethylol-4,5-dihydroxy ethylene urea (DMDHEU). Part 2: Pore size distribution determined by differential scanning calorimetry

Abstract The enthalpy of melting and the freezing point depression of European beech (Fagus sylvatica L.) wood modified with 0.8, 1.3, and 2.3 M 1,3-dimethylol-4,5-dihydroxy ethylene urea (DMDHEU) were determined at different levels of moisture content above the fibre saturation point by differential scanning calorimetry. The results permitted estimations of the amount of water bound to the cell wall, non-freezing water (NFW), and pore size distribution. The NFW of wood modified with DMDHEU, calculated on a dry wood basis, was not significantly lower than that of the control. The ratio of bound to total water present in the sample was higher in unmodified than in DMDHEU-modified samples. The proportion of pores with a diameter ≤30 nm was 70% of the total cell wall voids for wood modified with 2.3 M DMDHEU and 18% for unmodified wood. These results indicate that DMDHEU reduced the pore size of the samples by occupying the void space present in the cell wall.

Attempt to photostabilize paper made from high-yield pulp by application of UV screens in conjunction with thiols

Abstract The stabilization against photoinduced brightness reversion of peroxide-bleached stoneground wood pulp by two phenolic UV screens (methyl 3-hydroxy-4-benzoylphenoxy acetate (DHBE) and methyl 3-(2″-benzotriazinyl)-4′-hydroxy-5′-terbutylphenyl propanoate HBTE) and two polyethyleneoxythiols (2-(2′-methoxyethoxy)ethanethiol (MSH) and 2,2′-oxydiethanethiol (DSH), individually or in combination (DHBE + MSH and HBTE + DSH), was investigated. A synergistic photostabilization effect was observed between the thiol and the UV absorber, but was not retained during irradiation due to thiol consumption probably by Michael-type addition on the quinones, generated by light. Moreover, during the irradiation, the HBTE derivative was found to be very stable on paper in contrast with the DHBE compound. This effect was related to the presence in HBTE of a bulky substituent (tert-butyl) adjacent to the phenolic group which locks the molecule in a favorable conformation for proton transfer in the ground and excited states.

Comparative study of stone-ground wood pulp and native wood 3. Application of fluorescence spectroscopy to a study of the weathering of stone-ground pulp and native wood

Abstract The fluorescence spectra of chemically treated and weathered paper made from stone-ground wood pulp (SGWP) and thin sections of wood treated in a similar manner have been recorded. Very little difference was found between the paper and wood samples. Chemical treatment included reduction with sodium borohydride and photochemical bleaching with thiourea dioxide. The samples were subjected to photobleaching of the fluorescent chromophores, and the wood samples and paper exhibited a photochromic effect. Of particular significance was the observation that borohydride-reduced and thiourea-dioxide-photobleached wood perform differently in the photobleaching experiments from their paper counterparts. These differences are attributed to the mechanochemistry which occurs during pulping, producing species such as stilbenes which are present in the paper but not in the wood. When borohydride-reduced SGWP and wood are weathered, much of the short-wavelength fluorescence is lost and in increase in longer wavelength emission is observed. Reduction by borohydride of the weathered samples leads to partial recovery of the shorter wavelength fluorescence. These observations are interpreted as being due to photoreactions of 4-hydroxy-3-methoxycinnamyl alcohol residues.