Correlação entre morfologia, percolação elétrica e propriedades mecânicas de compósitos da blenda PLA/PBS com grafite expandido
Abstract
In recent years, researchers from industry and universities have focused
their interests in polymer nanocomposites, especially in multifunctional
composites. The composites made from nano expanded graphite ( nGE ) can
provide to the polymer matrix an innovative balance of structural, electrical and
thermal conductivity, electromagnetic shielding and improved barrier and wear
resistance properties. The increasing demand of using biodegradable polymers,
such as poly (lactic acid ) (PLA ) and its blends with poly ( butylene succinate)
(PBS), in packages of short lifespan with low resistivity requirements, motivated
this work. Nanocomposites of nGE with PLA and PLA / PBS blends were
evaluated on the effects of conductive nanofiller content and processing
methods in their rheological, mechanical, and electrical properties, in order to
correlate and possibly control the formation of the percolation network. The
nanographite had a major mechanical reinforcement effect in of the composite
with PLA / PBS, increasing all tensile properties. Through microstructural
analysis, it was was observed the selective localization of graphite particles in
PLA, forming a percolated co-continuous phase with PBS phase. This
phenomenon was identified as double percolation, result of the preferential nGE
gelation in PLA by the processes of coalescence of PBS and possible
crystallization of polymers in the blend. The PLA composites remained resistive,
since the nGE particles homogeneous dispersion was maintained. The lowest
resistivities were found in the samples of the blend processed by compression
moulding, more favorable process for the formation of the electrical percolation
network through the mechanisms mentioned above. The coalescence of PBS
phase proved to be determinant for the electrical percolation.