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Étude des interfaces thermoplastique-thermodurcissable obtenues par co-cuisson pour la réalisation de pièces composites hybrides de haute performance pour l’aviation

Demanet, Arnaud
(2019)

Files

Demanet_21751100_2019.pdf
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Details

Supervisors
Bailly, Christian
Faculty
Ecole polytechnique de Louvain
Degree label
Master [120] : ingénieur civil en chimie et science des matériaux
Abstract
enThis work studies the effects of surface treatments on high performance polymers, polyphenylene sulfide (PPS) and polyetheretherketone (PEEK), to enhance surface properties to get better adhesion with a thermoset material, the 8552 epoxy resin. Two treatments are specially analysed, chemical etching by acid solution and oxygen plasma treatment. Thermoplastics are thermally analysed by differential scanning calorimetry (DSC) to define crystallinity of each polymer. Surface before and after treatment is characterized by contact angle measurement, attenuated total reflectance (ATR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscope (AFM). The experimental results show that surface energy is increased by surface treatments resulting from functional groups formation at surface. Surface roughness is increased as confirmed by AFM observation. Adhesion is consequently widely enhanced and proved by lap shear test. These results can be explained by the fact that surface treatments oxidize the hydrophobic surface of thermoplastic. This oxidation increases polarity, wettability and adhesion characteristics of the thermoplastic/epoxy resin. The interface is also characterized by SEM and shows some cracks between the two materials due to polymers shrinkage during the cooling. These cracks are less coarse when treament is applied on thermoplastic surface. To show the effect of cristallinity, experiments are made on amorphous PEEK and semicrystalline PEEK. Results show that adhesion is weaker by using an untreatd semicrystalline polymer than an untreated amorphous polymer due to decreased interdiffusion by cristalline phases. After the application of a treatment, this difference disappeared and interface presents a better strength. This work studies also the hydrophobic recovery of thermoplastic by ageing. Surface energy decreases widely with time due to diffusion of functional groups in the bulk material and thermoplastics are no longer suitable to get a good adhesion with thermoset resin.