Processing of nanocomposites PLA/graphite using a novel elongational mixing device
Auteurs
R. Ibarra-Gómez, R. Muller, M. Bouquey, J. Rondin, C.A. Serra, F. Hassouna, Y. El Mouedden, V. Toniazzo, and D. Ruch
Référence
Polymer Engineering and Science, vol. 55, no. 1, pp. 214-222
Description
Expanded
graphite (EG) was added to polylactic acid (PLA) and then fully mixed in
a novel elongational mixing device (RMX) to obtain PLA/EG
nanocomposites. The operation of the new mixer device is based on the
induced multiple passages of material (by means of reciprocating
pistons) at different flow speeds through a short capillary die, thus
creating convergent/divergent elongational flows. Highly homogeneous
materials were obtained at all mixing conditions and particle size
ranged from hundred to several hundreds of nanometers. Also, X-ray
diffractograms showed different intensity of the characteristic peak of
EG (3% wt/wt EG was kept constant), suggesting partial exfoliation.
Furthermore, the molecular weight of processed neat PLA samples was
assessed in order to correlate the PLA degradation to morphology and
reinforcement mechanisms in the nanocomposites, as a function of the RMX
parameters. As well, final flow properties of neat PLA and EG compounds
were obtained by dynamic rheology. Thermomechanical degradation of PLA
was found to play a major role in the rheology of mixing. On the other
hand, PLA nanocomposites presented a storage modulus between 20 and 40%
higher than neat PLA. Finally, morphology comparison between the RMX and
an internal mixer, at the same mixing energy input, demonstrated a
higher dispersive mixing efficiency for the RMX.
