Dispersion improvement of carbon nanotubes in epoxy resin using amphiphilic block copolymers

International audienceInterface between Carbon NanoTubes (CNT) and epoxy matrix is admitted to play an important role in the dispersion quality and in the mechanical stress transfer. To improve the interfacial adhesion, we propose to chemically graft molecules onto CNT surface. To achieve this chemical modification, a controlled radical polymerization, named Nitroxide Mediated Polymerization NMP, is used to synthesize a diblock copolymer based on Acrylic Acid (PAA block) and Methyl MethAcrylate (PMMA block). In the present paper, this polymerization is performed "in situ ". The PAA block presents a good affinity with the CNT which enable grafting. The PMMA miscibility with epoxy is expected to give a good adhesion-between the CNT and the matrix-and to bring a better dispersion. In order to compare the chemical modification and the physical adsorption of the copolymers onto CNT dispersion, the same block copolymer was synthesized with and without CNT. The copolymer synthesis was controlled and characterized by different methods as NMR 1H (conversion and composition), SEC (molecular weight) and TGA (grafting density). We show that the better dispersion quality and better physical properties have been obtained with grafted CNT

VISCOPLASTICITÉ DYNAMIQUE DE POLYCARBONATES AUX GRANDES VITESSES DE DÉFORMATION, RELATIONS STRUCTURE-PROPRIÉTÉS

Les comportements rhéologiques de polycarbonates techniques sont étudiés à grande vitesse de distorsion et à grande vitesse de compression (102 s-1 - 5 103 s-1) en fonction de la température (10°C - 150°C) par des dispositifs à barres de Hopkinson. Pour le mode de compression, les résultats sont comparés avec ceux obtenus à très faible vitesse de déformation (10-3 s-1 - 10-1 s-1). On met en évidence dans ce dernier cas l'existence d'une vitesse de déformation critique correspondant à une transition de relaxation ; en outre l'influence d'un prétraitement thermique est aussi abordée.Rheological behaviours of engineering polycarbonates are investigated at high shear strain rates and at high compressive strain rate (102 s-1 - 5 103 s-1) for temperatures ranging from 10°C to 150°C, by means of Hopkinson pressure bar apparati. For the compressive mode, the results are compared to those ones obtained at low strain rates (10-3 s-1 - 10-1 s-1). A critical loading strain rate is pointed out, which is related to a relaxation transition. Moreover the influence of a prethermal treatment is studied

Amphiphilic diblock copolymers with adhesive properties: I. Structure and swelling with water

We study asymmetric block copolymers with the simple diblock AB architecture, in the case where the longer block A is both hydrophobic and "soft", whereas the shorter block B is hydrophilic and "hard". Materials with such a particular combination of physico-chemical and mechanical properties have distinctive advantages, in particular for designing water-compatible adhesive materials. The phase diagram is established, combining NMR and SAXS characterisations of the materials. The swelling with water is monitored through gravimetry and "time-resolved" SAXS. Indications of maintained adhesive properties in a wet environment are given