Extraction de nanofibrilles de cellulose à structure et propriétés contrôlées : caractérisation, propriétés rhéologiques et application nanocomposites

The cellulose nanofibrils (CNF), obtained by TEMPO oxidation of native cellulose microfibrils as colloidal aqueous suspensions, are biosourced nanoparticles having rheological and optical properties well adapted for the conception of new nanomaterials with high performance.The main purpose of this study was to control and optimize the conditions for preparing these NFCs extracted from date palm tree by examining the oxidation time and the number of passes through the homogenizer..The success of the reaction was demonstrated by FT-IR spectroscopy. The rate of the carboxylic groups has been calculated by conductometric titration and ranged between 221 and 772 mol / g of anhydroglucose. Morphological studies show that oxidized CNFs are very individualized by introducing negative charges on their surfaces that induce electrostatic repulsion forces between the fibrils. Particular attention has been given to the viscoelasticity of oxidized-TEMPO CNF suspensions whose monitoring was carried out by a rheometer ARES-G2TA. These nanocharges were incorporated in a thermoplastic (PVAc) and nanocomposite materials obtained were characterized by SEM, TGA, DSC, DMA and mechanical testing.Les nanofibrilles de cellulose (NFC), obtenus par oxydation TEMPO des microfibrilles de cellulose native sous forme de suspensions colloïdales aqueuses, sont des nanoparticules biosourcées ayant des propriétés rhéologiques et optiques particulièrement séduisantes pour la conception de nanomatériaux à haute performance. Le but principal de cette étude était de contrôler et optimiser les conditions de préparation de ces NFCs extraites du rachis de palmier dattier en examinant le temps d'oxydation et le nombre de passe à travers l'homogéinsateur.La réussite de la réaction a été démontrée par spectroscopies FT-IR. Le taux de groupements carboxyliques a été calculé par dosage conductimétrique et était compris entre 221 et 772 µmol/g d'anhydroglucose. Les études morphologiques montrent que NFCs oxydées sont assez bien individualisés grâce à l'introduction des charges négatives à leur surface qui induisent des forces de répulsion électrostatique entre les fibrilles. Une attention particulière a été accordée à la viscoélasticité des suspensions NFC oxydées TEMPO dont le suivi a été réalisé par un rhéomètre ARES-G2TA. Ces nanocharges ont ensuite été incorporées au sein d'un thermoplastique (PVAc), puis les matériaux nanocomposites obtenus ont été caractérisés par MEB, ATG, DSC, DMA et par des tests mécaniques

Extraction of cellulose nanofibrils with structure and controlled properties : characterization, rheologic properties and nanocomposites application

Les nanofibrilles de cellulose (NFC), obtenus par oxydation TEMPO des microfibrilles de cellulose native sous forme de suspensions colloïdales aqueuses, sont des nanoparticules biosourcées ayant des propriétés rhéologiques et optiques particulièrement séduisantes pour la conception de nanomatériaux à haute performance. Le but principal de cette étude était de contrôler et optimiser les conditions de préparation de ces NFCs extraites du rachis de palmier dattier en examinant le temps d'oxydation et le nombre de passe à travers l'homogéinsateur.La réussite de la réaction a été démontrée par spectroscopies FT-IR. Le taux de groupements carboxyliques a été calculé par dosage conductimétrique et était compris entre 221 et 772 µmol/g d'anhydroglucose. Les études morphologiques montrent que NFCs oxydées sont assez bien individualisés grâce à l'introduction des charges négatives à leur surface qui induisent des forces de répulsion électrostatique entre les fibrilles. Une attention particulière a été accordée à la viscoélasticité des suspensions NFC oxydées TEMPO dont le suivi a été réalisé par un rhéomètre ARES-G2TA. Ces nanocharges ont ensuite été incorporées au sein d'un thermoplastique (PVAc), puis les matériaux nanocomposites obtenus ont été caractérisés par MEB, ATG, DSC, DMA et par des tests mécaniques.The cellulose nanofibrils (CNF), obtained by TEMPO oxidation of native cellulose microfibrils as colloidal aqueous suspensions, are biosourced nanoparticles having rheological and optical properties well adapted for the conception of new nanomaterials with high performance.The main purpose of this study was to control and optimize the conditions for preparing these NFCs extracted from date palm tree by examining the oxidation time and the number of passes through the homogenizer..The success of the reaction was demonstrated by FT-IR spectroscopy. The rate of the carboxylic groups has been calculated by conductometric titration and ranged between 221 and 772 mol / g of anhydroglucose. Morphological studies show that oxidized CNFs are very individualized by introducing negative charges on their surfaces that induce electrostatic repulsion forces between the fibrils. Particular attention has been given to the viscoelasticity of oxidized-TEMPO CNF suspensions whose monitoring was carried out by a rheometer ARES-G2TA. These nanocharges were incorporated in a thermoplastic (PVAc) and nanocomposite materials obtained were characterized by SEM, TGA, DSC, DMA and mechanical testing

Impact of TEMPO-oxidization strength on the properties of cellulose nanofibril reinforced polyvinyl acetate nanocomposites

International audienceNanocomposites of polyvinyl acetate (PVAc) reinforced with two different TEMPO-oxidized cellulose nanofibrils (CNF) were prepared by casting/evaporation method. These two sets of CNF, designed as CNF-O-5 min (5 min of oxidation) and CNF-O-120 min (120 min of oxidation), are different by their surface charge, geometrical characteristics and crystallinity index. The weight fraction of CNF was changed from 1 to 10 wt%. The mechanical and thermal properties of the nanocomposite films were studied by dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and tensile tests, and their morphology was investigated by scanning electron microscopy (SEM). For all nanocomposites, increasing amounts of CNF led to a significant increase in the mechanical properties (increase in Young’s modulus and tensile strength) and in the water uptake. On the other hand, the lost of transparency became very significant when the weight fraction of CNF exceeded 3 wt%. The comparison between the two sets of CNF showed that PVAc/CNF-O-5 min nanocomposite films had a tendency to display higher tensile strength and elastic modulus than those of PVAc/CNF-O-120 min films. In addition, the water uptake is higher for PVAc/CNF-O-120 min. Finally, the thermal stability analyses for PVAc/CNF films show that shorter and more charged fibrils (CNF-O-120 min) appear to slightly increase the thermal stability compared to other larger and less charged fibrils (CNF-O-5 min). All these results are discussed in connection with the CNFs characteristics

Investigation on the Thermoforming of Pmsq-Hdpe for the Manufacture of a NACA Profile of Small Dimensions

Unmanned aerial vehicles (UAVs) or drones are attracting increasing interest in the aviation industry, both for military and civilian applications. The materials used so far in the manufacture of UAVs are wood, plastic, aluminum and carbon fiber. In this regard, a new family of high-density polyethylene (HDPE) nanocomposites reinforced with polymethylsilsesquioxane nanoparticles (PMSQ), with mechanical performances significantly superior to those of pure HPDE, has been prepared by a fusion-combination process. Their viscoelastic properties were determined by oscillatory shear tests and their viscoelastic behavior characterized by the Lodge integral model. Then, the Lagrangian formulation and the membrane theory assumption were used in the explicit implementation of the dynamic finite element formulation. For the forming phase, we considered the thermodynamic approach to express the external work in terms of closed volume. In terms of von Mises stress distribution and thickness in the blade, the results indicate that HDPE-PMSQ behaves like virgin HDPE. Furthermore, its materials, for all intents and purposes, require the same amount of energy to form as HDPE