PAZ, R. A.; http://lattes.cnpq.br/2848266629474356; PAZ, Renê Anísio da.
Résumé:
The effect of polyamide 6 (PA6) molecular weight on the development of
polymer/layered silicates nanocomposites prepared by the melt intercalation
technique was studied in this work. The clay was treated with a quaternary
ammonium salt (Genamin) to obtain the organoclay (OMMT). It was
characterized by X-ray fluorescence (XRF), Fourier Transform infrared
spectroscopy (FTIR), thermogravimetry (TG) and X-ray diffraction (XRD). The
results of these analyses showed the incorporation of the salt in the clay
structure, confirming the organophilization. In order to obtain the polyamide
6/organoclay nanocomposites masters of PA6: organoclay (1:1) were prepared
to facilitate the mixture in the counter-rotational twin screw extruder. The
obtained masters were incorporated in the polymer matrix at a content of 3 wt.%
of clay and then, the pellets were injected using a Fluidmec injection molding
machine. The materials were characterized by torque rheometry, melt flow
index, Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD),
differential scanning calorimetry (DSC), transmission electron microscopy
(TEM), mechanical properties (tensile and Izod impact strength), heat deflection
temperature (HDT) and dynamical-mechanical thermal analysis (DMTA). The
results of torque rheometry and melt flow index showed that the presence of
organoclay in the polyamide 6 increased the torque in relation to the untreated
clay and, the bigger the shear rate the smaller the viscosity of the material,
confirming the pseudoplastic behavior of the system. The patterns of XRD of
the films of PA6/organoclay showed that all systems presented predominance
exfoliated structure which was confirmed by TEM. However, the results of XRD
and TEM of the specimens obtained by injection molding showed exfoliated
and/or partially exfoliated structure. The crystallinity degree of nanocomposite
obtained by DSC, its mechanical properties of tensile and HDT were enhanced
in relation to pure PA6. In general, the polyamide 6 with high molecular weight
nanocomposites presented more significant results of these properties. On the
other hand, its Izod impact strength was reduced. The DMTA analysis showed
that the incorporation of organoclay in the polymer matrices increased the rigidity (E*) of the system and the tanS decreased for all studied temperatures,
confirming the reinforcing effect of the clay in the polymer. Hence, one can say
that the systems with high molecular weight polyamide 6 presented better
properties in relation to the ones with lower molecular weight.