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

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

Anaheim

Conferencia; ANTEC® Anaheim 2017; 2017

SPE (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 any improvement in tensile strength and elongation at break and were very brittle compared with PLA films. Reactive blends films showed a significant improvement of elongation at break (50%) with a better performance of films produced with DCP than films produced with L101. PLA-g-TPCS and PLA-g-TPCS-GRH25 ? load of graphene (0.1 wt.%) - showed higher elongation at break with values of 30% and 100%, respectively than PLA films. However, improvements in tensile strength were not observed. SEM image of PLA-g-TPCS-GRH25 clearly showed that GRH25 sheets were pulled out completely and left some emptied spaces in the polymer matrix due to their weak interfacial adhesion to the PLA matrix, leading a significant elongation improvement thanks to formation of cavities around weakly attached GRH sheets to the PLA matrix under elongational stress.