Thèse de doctorat en Sciences des matériaux
Sous la direction de Gilbert Villoutreix.
Study on recycling of propylene and preparation of composite materials base on recycled polypropylene
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Due to the important number of highly appreciated properties such as high impact strength, high tensile strength, good chemical resistance, low density, and also rather low cost, polypropylene is among the most widely used thermoplastics in many industrial fields. However, like other recycled polymers, its properties usually decrease after the recycling process and sometimes are degraded to a poor levels of properties in order to direct re-employment. The recycled products need to be reinforced to take a good competition. In this field, the objective of the thesis initially was studied the influence of processing conditions and recycling parameters in twin screw extruder on structure of virgin initial polypropylene and on it’s properties. Then, from recycled and characterized products, we carried out the reinforced formulations having the equivalent or improved properties compared to initial properties. We studied the role of incidence of the introduced additives, in particular that of nanoclays and vegetables fibers on obtained composites. In parallel, we studied the concentration of chemical modified nanoclay and compatibilizer contents in the composite according to the traditional thermodynamic rules. The nanodispersion and the interaction matrix/clay were also investigated by using the Dynamic mechanical thermal analysis (DMTA), the X-rays diffraction (XRD), the Differential scanning calorimetry, the Scanning electron microscope (SEM) and the Rheological measurements). In the following step, we studied the process of introduction of bamboo fibers into to recycled polypropylene matrix by using a modular twin screw extruder to produce the composites in the form of transformable pellets. The objective here is to obtain “green” composite materials to substitution in keeping the mechanical properties required by the traditional specification conditions.