Influência do processamento no comportamento mecânico de nanocompósitos de poliamida 6 com nanosílica
Abstract
In this study nanocomposites of polyamide-6 (PA-6) reinforced with silica
nanoparticles (SiO2) were prepared in order to promote improved mechanical
properties for engineering applications. The nanoparticles’ surfaces were
chemically modified with the silane agent 3-aminopropyltrimethoxysilane (3-
APTMS) to improve the chemical and physical interactions between them and
the PA-6 matrix. Nuclear magnetic resonance analysis (NMR) and Fourier
transform infrared absorption spectroscopy (FT-IR) showed that 3-APTMS
grafting on nanoparticles surface was accomplished. The nanocomposites
mixing process was studied in two forms: by torque rheometry, using a torque
rheometer internal mixer; and in a co-rotating and intermeshing twin-screw
extruder. A preliminary study of the influence of processing variables at the
torque rheometer on the degradation of polyamide-6 matrix was performed. The
results showed that the greater the filling volume of the mixture in the chamber
and the rotational speed of the rheometer’s rotors, the lower the degradation of
the polyamide-6. Based on this preliminary study, compositions with 1, 2, and 4
% weight of SiO2 nanoparticles, both unmodified and chemically modified with
3-APTMS were prepared in the torque rheometer. The nanocomposites were
compression molded and it was observed that nanocomposites reinforced with
1 wt.% SiO2, both unmodified and surface-modified, presented the best tensile
properties. For the nanocomposite samples processed in the twin-screw
extruder, the influence of relevant variables – nanoparticle content, chemical
surface modification, physical form of the fed PA-6 (granule and powder),
rotational speed of screws and extruder feed rate – on mechanical, thermal, and
dynamic-mechanical properties were studied. The samples were afterwards
injection molded and it was observed that the samples produced using 1 wt.%
surface-modified and 100% finely ground PA-6 showed the higher tensile
modulus and yield strength values.