Processing of nanocomposites PLA/graphite using a novel elongational mixing device

01/01/2015

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.

Lien

doi: 10.1002/pen.23869

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