STUDY OF BLENDS OF POLY (LACTI ACID) WITH POLYPROPYLENE AND NANOCOMPOSITES WITH MONTMORILLONITE

Abstract

In  the  present  work,  the  influence  of  degradation  during  the  processing  in  the  tensile  properties  of  blends  of  poly  (lactic  acid), montmorillonite and two types of polyolefins as dispersed phases was studied. Polymers grafted with maleic anhydride were employed as the compatibilizing agents. The nanocomposites and their blends were prepared in an internal mixer at 200°C and characterized using solution  viscometry  of  the  PLA  phase,  infrared  spectroscopy  (FTIR)  and  transmission  and  scanning  electron  microscopy  (TEM  and SEM). The melt processing of the PLA produced its thermo-mechanical degradation and a steep decrease in its molecular weight. The large size of the dispersed phases in the PLA and the poor tensile properties of the blends without clay were attributed to the thermal degradation of the PLA matrix during their processing. Changes in the molecular weight of the PLA in blends without montmorillonite depend  on  the  type  of  disperse  phase  and  on  the  efficiency  as  emulsifier  of  the  compatibilizing  agent  employed.  The  presence  of montmorillonite slightly increased the Young’s modulus values of the blends. Smaller particle sizes of the dispersed phase were found in blends with the clay; however, optimal tensile properties were not found.