Polylactic Acid/Impact Modifier Blends

The effects of four impact modifiers: natural rubber (NR), poly(cis-1,4-isoprene) (IR), poly(acrylonitrile-co-butadiene) (NBR) and poly(ethylene-co-vinyl acetate) (PEVA), on the morphology, thermal and tensile properties by solution blending of poly(lactic acid) and 5 and 10 wt% impact modifier were investigated. Results showed that Young's modulus and T.S. at break decreased in all PLA/impact modifier blends. In addition, Young's modulus in all blends and T.S. at break in PLA/NR, PLA/IR and PLA/NBR blends was not significantly affected by the type and content of impact modifiers in the blends, but T.S. at break in PLA/PEVA blends was decreased by increasing the PVEA content from 5 wt% to 10 wt%. By contrast, the elongation at break significantly increased in all PLA/impact modifier blends and only PLA/NBR blends was affected by the content of impact modifier. Finally, the increase in ductility of all PLA/impact modifier blends confirmed the toughening capability of all impact modifiers. Thus, it is evident from tensile properties obtained indicated that PLA/impact modifier blends exhibit greater flexibility with all impact modifiers. Phase separation morphology of dispersion of impact modifier in PLA matrix indicating poor interfacial adhesion was observed. T-g and T-m of PLA/impact modifier blends exhibited almost the same as pure PLA, this suggested that there was no molecular interaction between PLA and impact modifiers, therefore, the PLA/impact modifier blends were immiscible.