화학공학소재연구정보센터
Polymer, Vol.46, No.16, 6009-6015, 2005
Time resolved study of oriented crystallisation of poly(lactic acid) during rapid tensile deformation
Poly(L-lactic acid) with 4% D-lactic acid comonomer has been drawn in the amorphous state at 80, 90, 100, 110 and 120 C at an extension rate of 4 s(-1) while simultaneously recording WAXS and SAXS patterns at intervals of 0.12 s. At 80, 90 and 100 C, crystallisation is very rapid (1-4 s(-1)) and follows a first order transformation process to give highly oriented crystals. SAXS patterns were barely detectable at these temperatures despite fractional crystallinity of similar to 0.2. At 110 and 120 degrees C, crystallisation was very slow (similar to 0.01 s(-1)) and gave rise to crystals with a lower degree of orientation. After eventual crystallisation at 120 degrees C, a two-point SAXS pattern develops with narrow lateral spread, suggesting `shish kebab' morphology. When the 80 degrees C drawn sample was annealed at 120 degrees C, a strong four point SAXS pattern develops. The change in drawing and crystallisation behaviour at higher draw temperature is attributed to the onset of chain retraction relaxation processes. The WAXS fibre pattern after annealing shows sampling on intermediate layer lines that is consistent with the a crystal form with a 10(3) helix. However, prior to annealing, sampling indicates a different, less defined helical configuration. (c) 2005 Elsevier Ltd. All rights reserved.