Stereocomplexation in the solution spun PLLA / PDLA blend fibers

Abstract

Solution-spun PLLA/PDLA blend fibers were obtained by the laboratory size spinning machine. The fibers obtained were drawn to various ratios at temperatures ranging from 80 to 140°C and subsequently annealed at 200°C under tension. Solution-spun fibers were highly crystallized during the coagulation process in the solution spinning and only the a-form homo-crystal of PLLA and PDLA were detected. Drawing of the fiber at temperatures between 80°C and 160°C did not promote the stereocomplexation between PLLA and PDLA. The drawn fiber seems to have two homo-crystal phases, one easily transformed to the streocomplex upon annealing at an elevated temperature and the other stayed either homo-crystal or melted during annealing and froze into the amorphous phase. The fibers drawn to higher ratios at higher temperatures, which showed a large melting peak of the homo-crystal at higher temperature region, kept homo-crystal phase even upon annealing at 200°C. On the other hand, the fibers drawn to lower ratios at lower temperatures, which show the single melting peak of homo-crystal at a lower temperature region, changed the structure from oriented homo-crystal to the oriented stereocomplex upon annealing. Due to the small content of oriented stereocomplex crystal and larger content of unoriented amorphous phase, the fibers annealed at an elevated temperature have fairly poor mechanical property.