Leader : Sbirrazzuoli Nicolas
External Collaborators : Société SICOMIN (France) ; Société DragonKraft (France) ; Région PACA ; Avantium Inc. (projet BIOFUR, The Netherlands) ; Kebony Inc. (projet Polywood, Danemark) ; SP Technical Research Institute (Sweden) ; Sao Paulo University (Brasil) ; Centre de Recherche sur les Macromolécules Végétales à Grenoble (CERMAV UPR CNRS 6301), University of Messina (Italy) ; CEMEF Mines-ParisTech (Sophia Antipolis)
Financial supports : Project and Région PACA PhD grants APO – BIOECOMAT, Région PhD grant ECOMOBIL ; 2 PhD thesis grants MESR ; 2 European projects : project "Polywood" ; The Research Council of Norway RCN (équivalent ANR Norvégienne ; European project "BIOpolymers and BIOfuels from FURan based building blocks" (BIOFUR), FP7-PEOPLE-2012-IAPP.
The materials based on biopolymers made from renewable resources are emerging, most with less advanced stages of development field. Plant biomass is an endless and diverse source of raw material. This project is to develop and characterize new bio-based thermoset composites. This theme revolves around three axes. The first relates to high performance composites for naval and aviation applications, electronics and the sports industry. Indeed , 95% of epoxy resins are produced from the diglycidyl ether of bisphenol A (DGEBA). This resin provides adhesives and composites with excellent properties. The objective of this work is to find alternatives to DGEBA but also for some polyurethanes used for applications that require more flexible materials. Resins are uncrosslinked prepolymers. In the presence of certain molecules called hardeners and under the action of heat or a catalyst, strong covalent bonds develop between the prepolymer chains, to form a crosslinked three-dimensional polymeric material, amorphous and disordered, but resistant, hard and infusible. We are working on finding new biobased resins and hardeners nontoxic capable of crosslinking in mild conditions in an eco-friendly chemistry. The main difficulty is to obtain high performance resins. Vegetable oils are among the most abundant renewable resources and therefore have a high potential value as a raw material for the manufacture of thermosetting polymers. Many studies exist on the synthesis and characterization of bioplastics from starch or corn, but few studies have been conducted on the thermoplastic from non-food plant parts and very little on the thermosets. Its high linolenic acid content makes linseed oil one of the most reactive vegetable oils. These oils are chemically modified to introduce specific functional groups to a specific type of polymerization. The presence of double bonds in the triglycerides opens the possibility for different functionalization. Epoxidation is one of the most interesting chemical modification and leads to epoxidized vegetable oils that result in thermosets by crosslinking using a "hardener" (reactive monomer). We study the complex reaction mechanisms involved in these reactions (i.e. successive copolymerizations or competitive homopolymerizations ) to vary the conditions for fostering the desired mechanism. The study of the rheological behavior during cure is very important because the physico-chemical phenomena of gelation / vitrification occurring during crosslinking interfere with chemical reactions, sometimes blocking reactions between reactive groups. This leads to incomplete polymerization, to the presence of residual monomers and lower end properties. Reinforcements based nanosilica or microfibrils are dispersed in the viscous matrices by chemical modifications of the surface of nanofillers to create covalent bonds nanofiller-matrix. Thus, these bio-based nanocomposites have near or higher performances compared to their petrosourced analogues. This improves the properties of bio-based composites to achieve performance closer to their petroleum analogues. It turns out that the organization of nanofillers should be perfectly controlled to achieve an improvement in macroscopic properties. Otherwise, these properties are not improved and may even be lower. Our studies therefore focus on understanding the nanofiller / matrix interactions. Sepiolite fibers have been chemically modified and grafted with magnetite. This allows orientation of these charges under a magnetic field and crosslink the system to freeze permanently the organization in order to increase the final properties through the induced orientation under field (coll. G. Bossis). A second class of materials is made from furfuryl alcohol (FA) and its derivatives - furfuryl alcohol from waste sugarcane, hardwood, corn or beet. The FA is one of 12 chemicals known to be capable of replacing some compounds derived from petrochemicals. In the presence of an acid initiator, the FA polymerize in polyfurfurylic alcohol (PFA). The FA may be impregnated in softwoods and after polymerization at the cell wall, it results in a composite "polymer timber". The modified wood also called " furfuryl wood " has a very good dimensional stability, increased resistance to external aggressions (insects, fungi, moisture, salinity) and improved mechanical properties. However, these improvements are highly dependent on cross-linking process of FA in the cell wall of wood. This crosslinking should be perfectly mastered and controlled. Within a European consortium of five partners (funded by the Norwegian Research Council Polywood Project), we focus on the thermal, kinetic and rheological aspects governing this crosslinking. Therefore, we study the cross-linking of the resin alone in the absence of wood. Then we will focus in a second time on the influence of the constituents of wood crosslinking. In addition, the PFA can be used as binder and wood glue or in the preparation of corrosion and fire resistant materials. PFA is also used as a binder for forming foundry molds and as a precursor of carbon materials and nanocomposites. It is obtained from furfural itself derived from the degradation of hemicellulose, i.e. from lignocellulosic residues (parts of the plant that cannot be used in the food industry). It combines the properties and reactivity of the heteroaromatic compounds with primary alcohols, due to the presence of a hydroxymethyl group. Thermosetting resins derived from polyfurfurylic alcohol (PFA) are a rare class of thermosetting fully biobased. However, crosslinked materials obtained from PFA have low elongation and high brittleness, which limits their applications. The first part of this work is to strengthen the matrix by introducing various natural fibers. These charges are fibers of flax or hemp, microfibrils or nanocrystals of cellulose, lignin. The second approach explored is the development of hybrid organic-inorganic nanocomposites.
An important part of this work concerns the structural and mechanical characterization to make the link between structure of nanoparticles and macroscopic properties. For improved properties, it is essential to fully control the organization of the nanofillers within the organic matrix. For nanosilica prepared by sol-gel process the dispersion obtained within the matrix is remarkable. Our efforts are focused on the study and implementation of two novel synthetic strategies to prevent particle agglomeration. The first is to achieve surface modifications nanofillers. The second is based on a "smart" functionalization to promote the creation of weak interactions during the phase dispersion of nanoparticles in the matrix and then create strong chemical bonds during curing to prevent nanocharges to re-aggregate. The role of connectivity of nanoparticles, which is related to the final properties of the material is related to the viscoelastic behavior of the composite characterized by mechanical measurements (coll. J. Persello). Finally, the last part of this project is to explore a new path of developing nanocomposites in which filler and matrix come from the same source. The new bio-inspired thermoset nanocomposites are obtained from cellulose. Cellulose is the most abundant natural polymer because it is the primary cell wall of higher plants and of certain animal species. In solid state cellulose, highly ordered crystalline structures alternate with zones of lower degree of organization. With a view to reducing environmental impacts, it is appropriate to take advantage of the natural macromolecular assembly of cellulose to avoid polymerization process often expensive in energy and in recycling of by-products. The objective is to develop a new bio-inspired nanocomposite thermosetting matrix in which filler and matrix will be both derived from cellulose without the need to introduce external fillers.
Fluides & Matériaux Complexes, Magnétorhéologie - Nanomatériaux, Matériaux Éco-compatibles
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