Poly(L-lactic acid) (PLLA) was selected to blend with poly(ethylene oxide) (PEO) in overcoming its intrinsically brittleness. The addition of PEO can dramatically accelerate the crystallization rate of PLLA. The morphology of unannealed and annealed PLLA/PEO (80/20) and (50/50) blends were studied using polarized optical microscopy (POM), scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Samples were annealed at temperatures from 90 to 125℃. The size of PLLA spherulites increased dramatically with the annealing temperature. SEM analyses of the water-etched PLLA/PEO blend samples and ToF-SIMS analyses of the blend thin films indicated that the PEO content was higher in the inter-spherulitic region then in the PLLA spherulites. The d...[ Read more ]

Poly(L-lactic acid) (PLLA) was selected to blend with poly(ethylene oxide) (PEO) in overcoming its intrinsically brittleness. The addition of PEO can dramatically accelerate the crystallization rate of PLLA. The morphology of unannealed and annealed PLLA/PEO (80/20) and (50/50) blends were studied using polarized optical microscopy (POM), scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Samples were annealed at temperatures from 90 to 125℃. The size of PLLA spherulites increased dramatically with the annealing temperature. SEM analyses of the water-etched PLLA/PEO blend samples and ToF-SIMS analyses of the blend thin films indicated that the PEO content was higher in the inter-spherulitic region then in the PLLA spherulites. The distribution of PEO between the two regions (i.e. the inter-spherulitic region and the region of PLLA spherulites) was found to be the key factor that determined the impact toughness of the unannealed and annealed PLLA/PEO blends. The unannealed PLLA/PEO (80/20) blend had the highest impact strength and very small spherulites compared to those of the samples annealed at 125℃. For the (50/50) blends, the sample annealed at 125℃ was the strongest one because it could undergo the plastic deformation within PLLA spherulites and sustain a higher level of stress in the inter-spherulitic regions.

Key words: poly(lactic acid); poly(ethylene oxide); spherulite size; interspherulitic boundary width, Izod impact toughness.