Siham Amirou

Effects of corona discharge treatment on the mechanical properties of biocomposites from polylactic acid and Algerian date palm fibres

In this paper, biocomposites materials based on date palm fibres (untreated or treated with corona discharge) as reinforcing elements and polylactic acid matrices were prepared and characterized. The objective of this study was to evaluate the mechanical properties of these biocomposites by modification of date palm fiber by using corona discharge treatment which results in a surface oxidation. The morphology of processed biocomposites was studied by scanning electron microscopy. It was found that treated fibers of the reinforced composite showed superior mechanical properties as compared with untreated fiber reinforced composites due to the enhanced adhesion between the treated date palm fiber and the polylactic acid matrix. Changes in the surface chemistry were investigated with Fourier Transform infrared spectroscopy. Moreover, morphological studies by scanning electron microscopy demonstrated that better adhesion between the treated fiber and the matrix was achieved. Such studies are of great interest in the development of environmentally friendly composites from biodegradable polymers.

Citric acid as waterproofing additive in butt joints linear wood welding

Citric acid was used to improve resistance to water of the welded joint of spruce along the end-grain-to-end-grain faces. The use of 10–20% citric acid as treatment during a very short time has been shown to markedly improve both the mechanical performance and the water resistance of welded spruce. Based on the results of the water resistance tests it appears that the application of citric acid as a natural waterproofing additive in wood welding is possible. The use of citric acid thus allows the preparation of welded wood joints satisfying the requirement of frequent short-term and long-term exposure to water. 13C NMR analysis indicated that lignin modification of the welded material is related to the improvement of water resistance and shear properties of the welded joints.

Melamine–Glyoxal–Glutaraldehyde Wood Panel Adhesives without Formaldehyde

(MGG’) resin adhesives for bonding wood panels were prepared by a single step procedure, namely reacting melamine with glyoxal and simultaneously with a much smaller proportion of glutaraldehyde. No formaldehyde was used. The inherent slow hardening of this resin was overcome by the addition of N-methyl-2-pyrrolidone hydrogen sulphate ionic liquid as the adhesive hardener in the glue mix. The plywood strength results obtained were comparable with those obtained with melamine–formaldehyde resins pressed under the same conditions. Matrix assisted laser desorption ionisation time of flight (MALDI ToF) and Fourier transform Infrared (FTIR) analysis allowed the identification of the main oligomer species obtained and of the different types of linkages formed, as well as to indicate the multifaceted role of the ionic liquid. These resins are proposed as a suitable substitute for equivalent formaldehyde-based resins.

Investigation of Chemical, Physical and Mechanical Properties of Algerian Date Palm Wood

Abstract In Algeria, the aging of palms is a significant constraint, since 30 % of the palms are over the age of production and they will consequently waste planting areas. A series of experiments have been accomplished to observe the possibility of converting the date palm stem into valuable woodworking products. This paper reports the results of an experimental investigation on the physical, chemical and mechanical properties of date palm trunk (Phoenix dactylifera L.) from Biskra oasis in Algeria. First, their chemical composition was studied and showed that they have amounts of holocellulose, lignin and cellulose similar to those encountered in softwood and hardwood. Results of flexural strength showed that the modulus of elasticity (MOE) and modulus of rupture (MOR) were 6647.04 MPa and 35.04 MPa, respectively. The compression modulus and strength were 5.35 MPa and 2.338 MPa in parallel compressive tests, respectively.

Reactions with Wood Carbohydrates and Lignin of Citric Acid as a Bond Promoter of Wood Veneer Panels

The reaction of citric acid with wood veneers was studied by Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP MAS 13C NMR) and matrix assisted laser desorption ionization time of flight (MALDI ToF) mass spectrometry. The analysis showed that reactions of citric acid occurred with both lignin and carbohydrate constituents of wood. The reactions occurring are esterifications between the carboxylic acid functions of citric acid and the numerous aromatic and aliphatic hydroxyl groups of the main wood constituents. Reaction of citric acid with glucose as a simple model compound of carbohydrates hydroxyl groups also yielded reactions leading to linear and branched oligomers by esterification. The result indicate that the reactions of esterification are accompanied in parallel by some internal rearrangements of lignin. The applied results on bonding wide flat wood surfaces such as veneers to obtain LVL panels yielded excellent strength results even if the conditions of pressing were more drastic than what is usual for this application. The applied bonding results have shown that citric acid has great potential to be used as a bio-binder for wood veneers.

Water resistance of natural joint of spruce produced by linear friction welding without any treatment

ABSTRACT This research work showed that spruce wood can be butt welded in a short time end-grain to-end-grain without any treatment. Wood welding has already been shown to be well adapted to the manufacture of wood structures of larger dimensions. When pressure increased, the welded material formed is of higher density and consequently the water resistance improved. The welded spruce samples present a much improved water resistance when the welding pressure was increased from 2.75 MPa to 3.75 MPa for the same welding time of 6 s. The welded interphase in end-grain-to-end-grain butt welding of spruce appears to occur by the formation of an interphase having the appearance of finger-joints. This is due to the different behaviours of the late and early wood rings of spruce during welding. This, by increasing the surface of contact, is shown to improve the water resistance of the original butt joint.