Tensile properties of reactive poly(lactic acid) and thermoplastic cassava starch blends functionalized with graphene sheets

RUBINO, MARIA; BHER, ANIBAL; AURAS, RAFAEL; SCHVEZOV, CARLOS E.; UNALAN, ILKE UYSAL

Anaheim, California

Congreso; ANTEC 2017 Society of Plastics Engineers Annual Technical Conference; 2017

Society of Plastics Engineers

Polylactic acid (PLA) was reactively blended with thermoplastic cassava starch (TPCS) and functionalized with Graphene Nano Platelets M-25 (XG Sciences, Inc., Lansing, Michigan) (GRH25). Reactive blend of PLA with TPCS (PLA-g-TPCS) was obtained by incorporating maleic anhydride (MA) with dicumyl peroxide (DCP) or 2,5-Bis (tert-butylperoxy)-2,5-dimethylhexane (Luperox® 101 or L101) as initiators. Master batch of the physical blend (PLA-TPCS), reactive blends, and functionalized blends were produced in a twin-screw extruder. The master batch was used to produce cast films of PLA, PLA-TPCS, PLA-g-TPCS and PLA-g-TPCS-GRH25. Tensile properties of the cast films were assessed using a universal testing machine. PLA films showed a typical brittle behavior with poor elongation at break (9%). PLA-TPCS films did not show improvement in tensile strength or elongation at break being very brittle when compared to PLA films. Reactive blends films showed a significant improvement of elongation at break (50%) with an improve film performance for films produced with DCP than films produced with L101. PLA-g-TPCS and PLA-g-TPCS-GRH25 with 0.1 wt.% graphene showed higher elongation at break with values of 30% and 100%, respectively; however, no improvements on tensile strength were observed. SEM image of PLA-g-TPCS-GRH25 clearly showed that GRH25 sheets were pulled out completely and left emptied spaces in the polymer matrix due to their weak interfacial adhesion to the PLA matrix. This led to a significant elongation improvement of the films due to formation of cavities around weakly attached GRH sheets to the PLA matrix.