Étude du comportement mécaniques et rhéologique des polymères

Abstract

In this work, we studied the mechanical and rheological behavior of two widely used semi-crystalline thermoplastic polymers: polypropylene (PP) and high-density polyethylene (HDPE). The main objective is to understand how molecular structure, crystallinity, morphology, and usage conditions influence the mechanical and viscoelastic properties of these materials. The mechanical behavior was analyzed through modeling and experimental tests (tensile, creep, and relaxation). Polypropylene is characterized by its stiffness and good tensile performance but becomes brittle at low temperatures, whereas high-density polyethylene offers excellent impact resistance. The deformation mechanisms are closely related to the microstructure of the materials (spherulites). The rheological study also highlighted the complex viscoelastic behavior of both polymers, with relaxation phenomena dependent on temperature, time, and frequency. This work sheds light on the key factors influencing their performance, providing a scientific basis for optimizing their industrial use and opening new perspectives for the development of advanced composites.