Effect of particle size on the surface properties and morphology of ground flax

Flax fibers were ground with a ball-mill and four fractions with different size ranges were collected by sieving. These were tested for water sorption, degree of polymerization (DP), copper number, hydroxyl number and analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and inverse gas chromatography (IGC). Significant differences were found between the properties of the flax fiber and those of the ground versions, including fragmentation of fibers, increase of water sorption, copper number, hydroxyl number and surface O/C ratio, and decrease of DP, crystallite size and dispersive component of surface energy (gammasd). Some parameters depended on the particle size: O/C ratio and hydroxyl number had local maxima at 315-630 μm, while gammasd increased steadily with the decrease of particle size. These relationships were explained by fiber disintegration, destruction of waxy surface layer, exposure of cellulosic components, increase of surface area and crystalline imperfections

Cellulose nanocrystal/amino-aldehyde biocomposite films

From the suspensions of cellulose nanocrystals (CNCs) derived from cotton and flax by acidic hydrolysis, transparent and smooth films were produced with different plasticizers and an amino-aldehyde based cross-linking agent in a wide composition range by a simultaneous casting and wet cross-linking process. The effect of cross-linker concentration on the optical and tensile properties and on the morphology of CNC films was investigated by various measurements. The interaction of films with liquid water and water vapour was also characterized by water sorption and water contact angle as well as performing a sinking test. Cross-linking improved the transparency, reduced the porosity and surface free energy, and prevented the delamination of CNC films in water at a concentration of 10% or higher. The surface of CNC films is basic in character and has an electron donor property. The CNC/amino-aldehyde films had a high tensile strength (45 MPa) and modulus (11 GPa)

Synthesis and applications of cinchona squaramide‐modified poly (glycidyl methacrylate) microspheres as recyclable polymer‐grafted enantioselective organocatalysts

Our work presents the immobilization of cinchona squaramide organocatalyst on poly(glycidyl methacrylate) solid support. Preparation of the well-defined monodisperse polymer microspheres was facilitated by comprehensive parameter optimization. Exploiting the reactive epoxy groups of the polymer support, three amino-functionalized cinchona derivatives were immobilized on this carrier. To explore the effect of the amino-linker, these structurally varied precatalysts were synthesized by modifying the cinchona skeleton at different positions. The catalytic activities of the immobilized organocatalysts were tested in Michael addition reaction of pentane-2,4-dione and trans--nitrostyrene with excellent yields (up to 98%) and enantioselectivities (up to 96% ee).Finally, the catalysts were easily recovered five times by centrifugation without loss of activity

Kiváló minőségű cellulóz alapú textíliák előállítása környezetbarát biotechnológiai eljárással = Creation of high-quality cellulose-based textile materials using environmentally friendly biotechnological process

Kutatócsoportunk több mint tíz éve dolgozik a textil biotechnológia területén. Az elmúlt időszakban - a most záruló OTKA pályázat keretén belül - elsősorban a pamut bioelőkészítésére koncentráltunk. Az enzimes előkészítés környezetbarát alternatívája a hagyományos víz-, vegyszer- és energiaigényes lúgos főzésnek, amellyel a nem cellulóz kísérőanyagokat (viaszok, pektin, fehérjék, lignin-tartalmú és színes anyagok) távolítjuk el a szálasanyagból. Kereskedelmi forgalomban kapható hidrolitikus enzimeket - cellulázok, pektinázok, xilanázok - alkalmaztunk pamut és len, valamint ezek keverékeinek bioelőkészítéséhez. Vizsgáltuk az enzimoldathoz adagolt komplexképzők hatását is a kísérőanyagok - elsősorban a viasz és pamutmaghéj - eltávolítására. Jellemeztük a szövetek fehérségét, fehéríthetőségét és színezhetőségét. A kutatás során nyert új eredmények alapján elkezdtük az oxidatív enzimek alkalmazását és hatásuk vizsgálatát a lignin-tartalmú kísérőanyagok bontásában. A drága oxidatív enzimeket szilárdfázisú fermentációval állítottuk elő. Az OTKA által több év óta támogatott kutatómunka tapasztalatai és eredményei jelentették az alapját annak a kutatás-fejlesztési pályázatnak, amelynek keretén belül 2005-ben és 2006-ban pamut, pamut/len és pamut/kender kötött kelmék bioelőkészítésének és biokikészítésének üzemesítése megvalósult. | Our research group has been working with enzymes in textile processes for more than ten years. In the frame of the present research project our primary research interest was in the area of biopreparation with special emphasis on cotton fabric. Enzymatic biopreparation of cellulosics is an environmentally-friendly alternative to the conventional alkaline scouring for removing the non-cellulosic 'impurities' (i.e. waxes, pectins, proteins, lignin-containing impurities and colouring matters, etc.) from greige fibres. Our research thrusts covered the application of commercial hydrolytic enzymes, such as cellulases, pectinases and xylanases for biopreparation of cotton and linen fabrics and their blends; the intensification of bioscouring with chelating agents; the evaluation of the degradation and removal of non-cellulosic matters, especially waxes and cotton seed-coat fragments; the characterization of the dyeing properties of the biopretreated fabrics, as well as the production of oxidative microbial enzymes by solid-state fermentation for efficient degradation of lignin-containing impurities of cotton and linen substrates. Based on the knowledge and experience came from the research supported by the OTKA for many years, implementation of biopreparation and biofinishing technologies in the finishing process of cotton, cotton/linen and cotton/hemp knitted fabrics was realized in 2005 and 2006, respectively, in the frame of a research & development project

Bioimprinted lipases in PVA nanofibers as efficient immobilized biocatalysts

Immobilization of lipases from Pseudomonas fluorescens (Lipase AK), Burkholderia (Pseudomonas) cepacia (Lipase PS) and lipase B from Pseudozyma (Candida) antarctica (CaLB) was investigated by entrapment in electrospun poly(vinyl alcohol) (PVA) nanofibers. The activity and selectivity of the lipases entrapped in PVA nanofibers were characterized in kinetic resolution of racemic secondary alcohols using acylation in organic media. Potential bioimprinting effect of eight substrate mimicking additives [polyethylene glycols (PEGs), non-ionic detergents (NIDs) and various organosilanes] was tested with the fiber-entrapped lipases. The nanofibrous lipase biocatalyst entrapped in the presence of the additives were also characterized by rheology, differential scanning calorimetry and scanning electron microscopy. In addition to the known lipase-bioimprinting agents (PEGs, NIDs), phenyl- and octyltriethoxysilane also enhanced substantially the biocatalytic properties of lipases in their electrospun PVA fiber-entrapped forms. The reasons of bioimprinting effect of several additives were rationalized by docking studies in the open and closed form of CaLB

Reusable Glucose-Based Crown Ethers Anchored to PVC

The recovery and reuse of the enantioselective catalysts produced by tedious work are important not only from the perspective of green chemistry, but also from the point of view of productivity. Some of the carbohydrate-based crown ethers prepared in our research group were able to generate significant asymmetric induction in certain cases. However, they were not recoverable after the synthesis. Therefore, we modified the most effective structure with a propargyl group so that it can be attached to a polymer with an azide–alkyne reaction. It was investigated whether the position of the bonding affects the activity of the crown ethers, hence, the propargyl group was introduced either to the side chain, to the anomeric center or to the benzylidene protecting group. To anchor the macrocycles, low molecular weight PVC was modified with azide groups in 4% and 10%, respectively. It was found that glucose-based crown ether bearing the propargyl group on the benzylidene unit and grafted to PVC in 4% has the highest activity regarding the enantioselectivity (77% ee). The catalyst was recoverable in the Michael addition of diethyl acetamidomalonate to nitrostyrene and it could be reused five times without the loss of enantioselectivity

Copper-containing resorcinol-formaldehyde networks

International audienceThe effect of copper ions on the polymerization and the structure of resorcinol-formaldehyde (RF) hydrogels, and on the resulting aerogels, is studied by a range of different techniques. Although the activation energy of the RF reaction in the presence of copper acetate is the same as with sodium carbonate, measurements by dynamic light scattering, small angle X-ray scattering, scanning electron microscopy and nitrogen adsorption reveal appreciable differences in the microscale structure and porosity of aerogels that have been synthesized with or without CuAc, before they are dried supercritically. The presence of copper ions produces a much finer mesh size on the submicron scale and increases the BET surface area of the aerogels to 2000 m/g, more than twice as much as those synthesized with sodium carbonate alone. The increase in the volume of wider pores detected by gas adsorption is even more striking. The observed effects can be attributed to the copper acetate

Drying of resorcinol-formaldehyde gels with CO2 medium

International audienceThe effect of using real supercritical conditions in the CO2 drying process on the structure and texture of resorcinol-formaldehyde networks is investigated by low temperature nitrogen adsorption, scanning electron microscopy and by small and wide angle X-ray scattering. If supercritical conditions are maintained throughout the whole extraction process the resulting networks exhibit much more developed porosity. The surface area of the supercritically dried gel, in excess of 500 m2/g, is more than twice that of the sample dried with liquid CO2. Pore volumes are also significantly higher in all pore classes. In the supercritical region the applied pressure strongly affects the porosity, while the effect of temperature is limited. Drying time also influences the total pore volume of the samples, but not the mesopore and micropore volumes. The volume filling character of the molecular adsorption process in this system is illustrated by the difference in surface areas measured by small angle X-ray scattering and that by nitrogen adsorption