Morphological and Rheological Study of Polypropylene/Clay Nanocomposites

C.O. ROHLMANN; L. M. QUINZANI; M. D. FAILLA

Buenos Aires

Congreso; XX IIInteramerican Congress of Chemical Engineering and V Argentinian Congress of Chemical Engineering; 2006

In the present study, a commercial organophilic montmorillonite was used to prepare polymeric nanocomposites based on polypropylene (PP) and maleic-grafted polypropylene (PPg) by melt compounding the three materials simultaneously.  The characterization of the clay and the composites was done using X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM, SEM) and rotational rheometry.  The purpose of the study is to analyze the relationship between the morphology of the composites and their linear viscoelastic properties.  The results from XRD and TEM characterization confirm that the mixing technique used to prepare the composites produces partial exfoliation of the clay platelets and that the presence of PPg as a coupling agent is important to achieve that exfoliation.  For clay concentration above a critical one, the nanocomposites show a solid-like behavior at low frequencies in small amplitude oscillatory shear flow.   The dynamic data show that, at a given temperature, the elastic and viscous moduli of the composites increase when the concentration of clay increases both, for a constant PP/PPg ratio and a constant PPg/clay ratio.  Moreover, the elastic modulus of the composites was observed to gradually increase as the temperature augments from one frequency sweep to the following. This effect of annealing is more noticeable at low frequencies. The increment in the modulus increases as the clay concentration increases and as the PPg concentration increases.  Evidence of phase segregation and of new chemical groups has been found in the annealed samples by TEM and SEM and by IR spectroscopy respectively.