Thermo-Hydro-Mechanical Wood Behaviour and Processing” Selected Papers

Abstract: Thermo-hydro-mechanical (THM) treatment is a combined action of temperature, moisture, and mechanical force, which leads to modified wood (THMW). Various types of eco-friendly THM processes have been developed to enhance wood properties and generate new materials, such as welding, densification, molding, bending, profiling, artificial aging, panel manufacture, and surface densification. The various transformation processes in the course of THM bring about positive effects in terms of the mechanical and physical properties as well as the biological durability. To the negative effects belong the loss in strength and fracture toughness, and one of the challenges is to minimize these negative aspects. The present paper reviews the chemical transformations processes during THM treatment in a closed processing system and presents the relationship between processing parameters and THMW properties. The discussion includes the problems associated with eliminating the set recovery of densified wood by THM posttreatments and the chemical origin of the relaxation of internal stresses induced by densification. Keywords: chemical-mechanical, chemistry, densification, fixation of compression set, moisture content (MC), temperature, woo

PERFORMANCE OF MUF RESINS FOR PARTICLEBOARDS BEFORE AND AFTER SPRAY-DRYING

Melamine-urea-formaldehyde (MUF) resins can be spray dried to obtain resins in powder form and indefinite shelf-life. Application as particleboard adhesives of such resins after redissolving them in water does yield resins of excellent performance as particleboard adhesives if the natural advancement caused by the heat in the spray-drier chamber is taken into account. CP MAS 13C NMR analysis of the spray-dried resin in powder form and thermomechanical analysis has shown some difference in behaviour in relation to MUF resins of the same level of water tolerance which have not been spray-dried. These small but significant differences can be ascribed to differences in resin structure

Structure and Oligomers Distribution of Commercial Tara (Caesalpina spinosa) Hydrolysable Tannin

Solvent extracted commercial Tara tanninextract have been examined by Matrix Assisted LaserDesorption/Ionisation Time-of-Flight (MALDI-TOF)mass spectrometry and by High Pressure LiquidChromatography (HPLC). The Tara extract has beenfound to be composed of a series of oligomers ofpolygallic acid attached by an ester link to one quinicacid. They constitute the oligomers in higherproportion in the extract. Other polygallic chains linkedto one only or two repeating units such as caffeic acidand methylated quinic, methylated gallic andmethylated caffeic acids are also present. Negativeion mode MALDI-TOF showed that somecarbohydrate residues appear to still be present,linked to the polyphenolic material of the extract buttheir proportion is very low as would be expected of asolvent extracted tannin

Resistance to decay fungi of ammonium borate oleate treated wood

Ammonium borate oleate molecule (ABO) produced from reaction between boric acid, ammonia and oleic acid was tested as wood preservative treatment against brown and white rot fungi according to European standards. This compound was prepared according to a previous study which has proved existence of synthesis reaction and effectiveness against termites (Lyon et al. 2007b). Four solutions of ABO in ethanol were then produced and impregnated sapwood specimens of Beech and Pine exposed to fungi Coniophora puteana and Coriolus versicolor. Efficiency thresholds were found in each case except for Pine samples exposed to Coniophora puteana. Combination of the biocide effect of boron, and the water repellence of fatty acids allowed to provide resistance of leached wood specimens against fungi

Furanic Rigid Foams, Furanic-Based Bioplastics and Furanic-Derived Wood Adhesives and Bioadhesives

In this chapter, we discuss pure furanic foams and tannin-furanic foams as fire-resistant, environmentally friendly, rigid biofoams. We also examine furanic wood adhesives in which a major furan portion is coupled with either synthetics or bioadhesives. In the case of furanic wood bioadhesives, the formulations developed were 90–100% biosourced. Equally, furanic rigid plastics of considerable mechanical resistance have also been developed and applied to angle-grinder discs and automotive brakes with very encouraging results

A novel fiber-veneer laminated composite based on tannin resin

Natural non-woven fiber was impregnated with a tannin resin and laminated with wood veneer for preparation of laminated composites. The tannin resin used showed a good compatibility with the natural fiber, and easy to assemble with the wood veneers. The tannin resin penetration into the wood veneer was observed by light microscopy. The laminated composite shows very good mechanical properties and water resistance. Shear force-displacement testing demonstrates that the laminated composite had a ductile behaviour under wet testing conditions. The laminated composite was prepared using 100% natural bio-renewable raw materials and had good properties compared to conventional plywood bonded with synthetic resin

A multistep bioinformatic approach detects putative regulatory elements in gene promoters

BACKGROUND: Searching for approximate patterns in large promoter sequences frequently produces an exceedingly high numbers of results. Our aim was to exploit biological knowledge for definition of a sheltered search space and of appropriate search parameters, in order to develop a method for identification of a tractable number of sequence motifs. RESULTS: Novel software (COOP) was developed for extraction of sequence motifs, based on clustering of exact or approximate patterns according to the frequency of their overlapping occurrences. Genomic sequences of 1 Kb upstream of 91 genes differentially expressed and/or encoding proteins with relevant function in adult human retina were analyzed. Methodology and results were tested by analysing 1,000 groups of putatively unrelated sequences, randomly selected among 17,156 human gene promoters. When applied to a sample of human promoters, the method identified 279 putative motifs frequently occurring in retina promoters sequences. Most of them are localized in the proximal portion of promoters, less variable in central region than in lateral regions and similar to known regulatory sequences. COOP software and reference manual are freely available upon request to the Authors. CONCLUSION: The approach described in this paper seems effective for identifying a tractable number of sequence motifs with putative regulatory role

Polypropylene Blend with Polyphenols through Dynamic Vulcanization: Mechanical, Rheological, Crystalline, Thermal, and UV Protective Property

International audienceTannin and lignin were blended with polypropylene (PP) through dynamic vulcanization technique. Their influence of mechanical property, crystallinity, thermal stability, as well as ultraviolet (UV) protection property on the PP matrix was investigated and compared with native tannin and lignin. According to our experimental results, tannin and lignin undergo dynamic vulcanization and were more compatible with the PP matrix. Besides, tannin and vulcanized tannin can perform as nucleating agents of PP because of their relatively small particle size. Moreover, vulcanized tannin/lignin have a better performance on the thermal stability of PP compared with native tannin/lignin, especially PP/vulcanized lignin blend. Furthermore, vulcanized tannin/lignin present better UV protective performance, concluded from fewer changes on surface morphology, carbonyl index, crystallinity, viscosity, and tensile property