کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5184056 | 1381037 | 2011 | 10 صفحه PDF | دانلود رایگان |
Crystallization of nonequimolar compositions of poly(d-lactic acid) with low-molecular-weight poly(l-lactic acid) (PDLA/LMw-PLLA) blends leads to formation of various fractions of stereocomplexed PLA (sc-crystallites) and homocrystallites (PDLA or PLLA). For the PDLA/LMw-PLLA blends within the composition window of LMw-PLLA content between 30 and 50Â wt%, only sc-crystal exists and no homocrystal is present. On the other hand, for PDLA/LMw-PLLA blends with excess PDLA, e.g. PDLA/LMw-PLLAÂ =Â 90/10, atomic-force microscopy (AFM) characterization on various stages of crystallization of sc-PLA crystal with PDLA homocrystal shows a repetitive stacking of excess PDLA on pre-formed sc-PLA crystal serving as crystallizing templates. The crystallization initially begins with string-like (fibril-like) PDLA lamellae, followed with PDLA aggregating on sc-PLA crystal into a bead-on-string crystal, then growing to thicker irregularly-shaped dough-like lamellae. Repetitive growth cycle from strings to bead-on-string lamellae continues on top of the dough-like lamellae as new substrates, until ending impingement of the PDLA spherulites.
Journal: Polymer - Volume 52, Issue 26, 13 December 2011, Pages 6080-6089