Abstract
The dielectric spectroscopy (DS), the differential scanning calorimetry (DSC), the scanning electron microscope (SEM) and the Fourier transform infrared spectroscopy (FTIR) measurements were performed on a poly(lactic acid) matrix reinforced by sisal fibers with different weight fractions (10% and 20%). The obtained dielectric spectra of the neat PLA and the PLA/sisal bio-composites covered a wide frequency range (from 10(-1) to 10(6) Hz) and a temperature domain varying from 20 degrees C to 140 degrees C as it serves to investigate the polymer dynamics and the interfacial properties. The DSC analysis, the SEM micrographs and the FTIR spectra were executed to determine the characteristic temperatures, the degree of crystallinity and the interaction between poly(lactic acid) and sisal fibers. The DS showed different relaxations: the beta relaxation, alpha process and the conduction phenomenon in the PLA matrix. Furthermore, the incorporation of sisal fiber generates additional relaxation processes known as the water polarization and the Maxwell-Wagner-Sillars (MWS) interfacial polarization. The PLA/sisal fiber interface properties were investigated through the calculation of the strength parameters increment epsilon(MWS) as well as the activation energy using the Havriliak-Negami model.