IDENTIFICATION OF KEY PARAMETERS IN DYNAMIC WETTING AND DEWETTING PHENOMENA WITH MOLTEN POLYMERS FOR COMPOSITE PROCESSING

M F Pucci , Benoît Duchemin (1) , M. Gomina (2) , J. Breard (2)

1 CESBIO - Centre d'études spatiales de la biosphère
2 LIMATB - Laboratoire d'Ingénierie des Matériaux de Bretagne

Introduction The main current research interest in the field of composite materials consists in minimizing the environmental impact of both materials and manufacturing. Having a good control of (bio)composite manufacturing implies a good knowledge of wetting phenomena occurring during impregnation of (natural) fibres by thermoset or thermoplastic polymers. It is known that capillary effects, and particularly capillary parameters like molten polymer surface tension and fibre surface energy, play an important role on impregnation. These effects coupled with the viscous ones are dominant during composite manufacturing [1,2]. The visco-capillary balance in dynamic wetting can be described by a hydrodynamic approach. In the literature, the de Gennes and Cox-Voinov theories [3] were used to fit experimental data (obtained mainly by optical methods) of liquid drops spreading on model substrates at standard conditions (room temperature). This procedure is not suitable in the case of fibres wetted by molten polymers for composite applications. Moreover, the influence of temperature and polymer molecular weight still remain unknown. The aim of this study was to set an experimental procedure that can be applied to fibres and polymers to investigate wetting dynamic and identify physical parameters such as a slip length, that can be inserted into numerical models to predict flow process [4]. The experimental procedure was validated on cellulosic films with different liquids. Paraffin oils are totally wetting liquids and they were used in order to evaluate the influence of temperature on wetting dynamics. Polyethylene glycols (PEGs) are partially wetting liquids; they were used to evaluate the effect of molecular weights (Mn) on wetting dynamics of molten polymers. An independent characterisation of the solid and of the liquids was carried out as well as solid/liquid dynamic wetting tests. Hydrodynamic models were used to fit the dynamic contact angle data. The results are meaningful for a better understanding of the influence of temperature, viscosity and liquid molecular weight on the dynamic contact angles and on capillary phenomena existing during the impregnation of fibrous reinforcements in composite processing.

Mots clés: dynamic wetting; capillary effects; molten polymers

Domaines: Matériaux

M F Pucci, Benoît Duchemin, M. Gomina, J. Breard. IDENTIFICATION OF KEY PARAMETERS IN DYNAMIC WETTING AND DEWETTING PHENOMENA WITH MOLTEN POLYMERS FOR COMPOSITE PROCESSING. THE 14TH INTERNATIONAL CONFERENCE ON FLOW PROCESSING IN COMPOSITE MATERIALS, May 2019, Luleå, Kulturens Hus, Sweden. ⟨10.1186/s40192-015-0032-1⟩. ⟨hal-02394157⟩