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Communication Dans Un Congrès Année : 2017

Self-reinforcement process of 100% thermoplastic composites by in-situ fibrillation

Résumé

This report deals with processes suitable for the preparation and forming methods of 100% polymer/polymer thermoplastic composites by the in situ fibrillation technique. The structured immiscible thermoplastic polymer blends obtained are a specific class of composites where the minor phase is in the form of filaments dispersed through the major phase and acts as “meltable solid fillers”. Because they are exclusively based on thermoplastic polymers, these structured materials can provide an interesting solution to the problems of lightening to equivalent mechanical performances due to the low density of the polymer fiber while preserving the recyclability potential of the thermoplastic polymer blends. Conventionally, the manufacture of thus structured products is decomposed in two stages. The first step is the compounding of a blend of two immiscible polymers followed by drawing (hot or cold, i.e. above or below the glass transition temperature of the dispersed phase), cooling and quenching of the fibrillar morphology. The possibility of obtaining this morphology is directly related to the viscosity and elasticity ratios of the two materials, under the conditions induced by their flow in the extrusion and drawing processes. The second step, of forming process (by extrusion or injection) shall be carried out under conditions of temperature, strain rate deformation and residence time which make it possible not to alter, or to minimize the alteration, of the fibrillar structure previously obtained. For this purpose, the forming temperature of the dispersed phase must be 30 ° C higher than that of the matrix. Thus, taking into account the constraints imposed on the one hand for obtaining the fibrillation of the dispersed phase during compounding and stretching and on the other hand for preserving the fibrillar structure during forming process, the number of pairs of polymers adapted to these processes with an industrial interest is generally relatively limited. Another approach is proposed here with the aim of extending the spectrum of the couple of polymers that can be used. The goal is to circumvent the constraints associated with the forming process stage by promoting fibrillation during this step and not only during the first compounding stage. This can be achieved, for example, by imposing a high stretching in the feed system of an injection mold. This strategy has been successfully implemented for several pairs of polymers, including PLA / PA11 blends. In this particular case, the resulting structure from the extrusion and injection steps is nanofibrillar (diameter of the PA11 fibers of the order of 500 nm) and allows correcting the fragility of the PLA matrix without significant degradation of neither its resistance nor its rigidity in tensile. The achievement of this result requires a thorough knowledge of the shear and elongation behavior of each of the materials under the temperature and strain rate conditions induced in each of the steps of the compounding and forming processes.
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Dates et versions

hal-01528799 , version 1 (29-05-2017)

Identifiants

  • HAL Id : hal-01528799 , version 1

Citer

Mohamed Yousfi, Jeremie Soulestin, Marie-France Lacrampe, Patricia Krawczak. Self-reinforcement process of 100% thermoplastic composites by in-situ fibrillation. POLYMERIC MATERIALS AND THE TRANSPORT INDUSTRY A Key contribution to mobility and weight saving, SFIP-IMT Lille Douai-GPA, May 2017, DOUAI, France. ⟨hal-01528799⟩
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