Rheological behavior of short Alfa fibers reinforced Mater-Bi® biocomposites

Abstract

This paper investigates the viscoelastic behavior in the melt of biocomposites of Alfa fibers dispersed in a polyester-starch bioplastic of the Mater-Bi® type. Biocomposites with three kinds of short Alfa fibers (untreated or treated with alkali solutions at 1% or 5%) and at various filler contents were prepared by means of twin screw extrusion. The rheological properties of such biocomposites have been studied in oscillatory shear at 140, 160 and 180 °C at frequencies varying from 100 to 0.01 rad/s in the viscoelastic linear domain. The influence of fiber loading, alkali treatment of fibers, and temperature on the viscoelasticity of biocomposites was examined. Dynamic moduli increase with increasing fibers content. In addition, biocomposites exhibit a plateau of the storage moduli at low frequencies, indicating a percolated fibers network. This low frequency elastic behavior is enhanced by the treatment of the fibers.The ratio of storage modulus of biocomposites to that of the neat matrix at low and high frequency is used to characterize the influence of the fiber content and of the concentration of alkali treatment of Alfa fibers on both percolation and hydrodynamic effects. This made it possible to sense the effect of these parameters on the dispersion process of Alfa fibers in the biopolymer matrix.