Nathalie Leblanc

Structural investigation and thermal stability of new extruded wheat flour based polymeric materials.

In this study, we compare physical properties of wheat starch and wheat-flour based materials. The comparison has been done using thermogravimetric, calorimetric, X-ray diffraction, mechanic and morphologic experiments conducted on a series of wheat-flour extruded materials. The wheat flour used here can be understood as a by-product of the farm-produce wheat flour. All data obtained by means of these experimental methods allow us to conclude that, basically no significant difference exists between our wheat-flour based and wheat-starch based materials. Only one clear difference occurs for the strain to break value which decreases by about 30% for wheat-flour based materials.

Thermal behavior of chemically treated and untreated sisal fiber reinforced composites fabricated by resin transfer molding

Using thermogravimetric analysis (TGA), the thermal behavior of sisal fibers and sisal/polyester composites, fabricated by resin transfer molding (RTM), has been followed. Chemical treatments have been found to increase the thermal stability, which has been attributed to the resultant physical and chemical changes. Scanning electron microscopy (SEM) and infrared (FT-IR) studies were also performed to study the structural changes and morphology in the sisal fiber during the treatment. The kinetic studies of thermal degradation of untreated and treated sisal fibers have been performed using Broido method. In the composites, as the fiber content increases, the thermal stability of the matrix decreases. The treated fiber reinforced composites have been found to be thermally more stable than the untreated derivatives. The increased thermal stability and reduced moisture behavior of treated composites have been correlated with fiber/matrix adhesion.

Are 100% Green Composites and Green Thermoplastics the New Materials for the Future?

A review of the history of the evolution of material science and material technology shows us that one tendency for the future could be the use of agriculture resources. In this work, we review the performances of one of these resources, that is, wheat flour. We show that it is possible to get thermoplastic films with properties quasiequivalent to what is obtained for expensive pure starch. By adding natural fibres, composites are also obtained. These composites exhibit performances which allow their use only for short duration.

Research Article. Role of ascorbic acid and iron in mechanical and oxygen absorption properties of starch and polycaprolactone multilayer film

Abstract A trilayer film based on thermoplastic starch (TPS) for the core layer and poly(ε-caprolactone) (PCL) for the skin layers was obtained by coextrusion. Ascorbic acid and iron powder were added at respectively 15% and 1.5% w/w in the TPS layer for their capacity to act as oxygen scavenger, making the film usable as active food packaging. This study demonstrates that these compounds also play a role in the interactions between the different layers. FTIR measurements show that ascorbic acid migrates at the interface between TPS and PCL, where it acts as a compatibiliser between both polymers, probably by creating new interactions between polar functions of both polymers. This leads to a better adhesion of the different layers, demonstrated by the increase of the adhesion energy from 4.10−3 N·mm−1 for the multilayer film TPS-PCL to 12.10−3 N·mm−1 for the multilayer film containing the active components. Thanks to this compatibilising effect, the mechanical properties of the multilayer film containing ascorbic acid and iron are widely improved with an average maximal tensile strength of 7 MPa, against 3.7 MPa for the multilayer film without the active components and with an elongation at break of respectively 1450% against 290%. However, despite the hydrophobicity of PCL, the water sorption of the TPS-based layer is only slightly reduced. The multilayer film shows active oxygen scavenging properties but the rate of this reaction is divided by two compared to the active film without PCL layers (15 days to reach less than 1% oxygen for the active film without PCL layers and approximately 30 days to reach the same oxygen level with the multilayer active film).

Hydrophobic surface treatments of sunflower pith using eco-friendly processes

The aim of the present paper is to report the reduction of the water uptake of sunflower pith, sustainable raw by-product without current added-value in oilseed crops production. The water-sensitivity is ascribed to its structure, because mainly constituted of carbohydrates, due to the formation of additional hydrogen bondings with water molecules. Two environmentally-friendly approaches were applied to provide a modified layer presenting water resistance in surface of sunflower pith in order to keep its low-density property. The first approach based on vegetable oil corresponds to thermal and photochemical treatments. A thin layer of virgin or acrylated epoxidized soybean oil was sprayed on the pith surface, and thereafter was thermally cured or photocured, respectively. The second approach consisted in a solventless chemical modification of the pith surface by a cold plasma treatment. Both approaches were successfully performed: water resistance of sunflower pith was clearly enhanced, especially with oil-based treatments; while maintaining its integrity. Developing new and promising ecological water-resistant products of low density from sunflower pith is thought of increasing interest with potential practical applications.

Morphologie et rhéologie de biocomposites à base d’amidon plastifié en écoulement élongationnel RMX

RÉSUMÉ. Cette étude porte sur l’étude du comportement thermomécanique et rhéologique des biocomposites d’amidon formulés par un mélangeur à écoulement élongationnel (RMX). Ce dispositif est basé sur un concept original qui consiste à mélanger de la matière de manière continue dans un système très étanche. Par rapport aux mélangeurs de laboratoires existants, l’écoulement dans le mélangeur est caractérisé par une forte contribution des flux d’écoulements élongationnels ce qui permettra d’augmenter la dispersion des constituants du mélange multiphasique et la capacité de mesurer directement l’évolution des propriétés rhéologiques des mélanges. Tout d’abord, l’impact des paramètres du procédé (température, vitesse de la vis) sur la qualité et les propriétés structurales de l’amidon plastifié (TPS) ont été examinés par DRX. Ensuite, nous avons élaboré diverses formulations à base d’amidon plastifié et d’anas de lin à différentes teneurs, et examiné l’évolution la viscosité du mélange in situ en fonction de la vitesse de cisaillement et le nombre de cycle de mélange. L’évolution des propriétés microstructurales des biocomposites à base d’amidon est également analysée par diffraction des rayons X (DRX), thermomécanique (DMA) et dégradation thermique (TGA).

Valorisation de coproduits agricoles dans des panneaux composites biosourcés

In the aim of agricultural byproduct valorization and wood resource preservation, composites particleboards have been elaborated from two agricultural residues: flax shives and sunflower bark. The particleboards have been processed by two different ways: with addition of classical synthetic glue (urea-formaldehyde) or without any extern binder. The boards show variable mechanical responses to the process (with or without glue) depending on their flax shives or sunflower bark proportions. The process and the binder used must be adapted to the type of agroresource used to perform these particleboards. All the studied composite materials show good thermal insulation properties. A 100 % biobased particleboard with good cohesion has been obtained from flax shives. MOTS-CLÉS : valorisation d’agroressources renouvelables, anas de lin, panneaux composites thermopressés, écorce de tournesol, propriétés mécaniques et thermiques, résistance à l’eau.