Rheological study of mica‐filled polypropylene as influenced by a coupling agent

Abstract The rheological behavior of mica‐filled polypropylene (PP) composites was investigated within the domain of linear viscoelasticity. The effect of mica concentration and of a silane coupling agent on material functions such as the complex viscosity (η*), the storage modulus (G') and the loss modulus (G") was examined. The dimensions of mica flakes were measured before and after coating with silane. The affinity of PP for the treated and non‐treated mica was characterized. It was found that, for low mica concentration (<30% by weight) the composite exhibits the classical viscoelastic behavior of a homogeneous material. For higher mica concentration, the material shows a strong heterogeneity as evidenced by an important drift at low frequencies in a Cole‐Cole representation. It was also found that the presence of a silane coupling agent moves this critical concentration value up to 40% by weight.