Bio-Composites Based on Poly(lactic acid) Containing Mallow and Eucalyptus Surface Modified Natural Fibers

In this work poly(lactic acid) (PLA) composites containing modified natural fillers obtained from physically and chemically treated mallow and eucalyptus fibers were prepared and characterized. The fibers were submitted to different alkaline and acid hydrolysis methods. The results showed that chemical treatment improved the thermal stability of the mallow fibers and reduced that of the eucalyptus fibers; however, there was a significant increase in the degree of crystallinity in both fibers. After the thermal and morphological analysis, the treated fibers were added to a commercial PLA matrix at 5 wt% content in a twin-screw Haake Minilab mini-extruder. First, the neat PLA was processed at 180 A degrees C at 60, 120 and 180 rpm for 5 min to adapt the parameters to the material's rheological characteristics. According to the results, the best conditions were obtained when processing at 120 rpm; subsequently, all of the composites were prepared using this speed. Then, the composites were characterized showing that the addition of fibers to the polymer matrix improved stiffness, which was more significant in the case of the PLA/eucalyptus fiber composites, where the treatment applied to the fibers decreased the fiber diameter and improved the surface adhesion.