pps proceeding - Abstract Preview
pps proceeding
Symposium: S02 - Films and Fibers
Oral Presentation
 
 

In-situ Nanofibrillation of Stereocomplexed Polylactides: Processing condition, Rheology, crystallization, morphology development and Foamability

Jalali Amirjalal (1), Park Chul B (1)*

(1) University of Toronto - Ontario - Canada

This study presents the melt-spinning of a series of asymmetric stereocomplex polylactides (sc-PLA) blends. The compounds of linear PLLA and low and high-molecular weight as well as branched PDLAs were used to prepare sc-PLAs. DSC heating thermograms of the samples showed two melting temperatures around 170 and 210 °C which were, respectively, ascribed to homo and stereocomplex crystals. Accordingly, the racemic blends of poly (l-lactide) and poly (D-lactide) (PLLA 95 wt%/PDLA 5 wt%) were subjected to a high speed single-step spunbond process. The samples were drawn at 190 °C, between the homo and stereocomplex crystals melting temperature, and 230 °C, above the stereocomplex crystals melting temperature. Scanning electron microscopy images showed that the fibers in the range of 10-50 μm were generated. Oscillatory shear rheological measurements revealed that the drawn stereocomplex PLA (sc-PLA) samples had a substantially higher viscosity and storage modulus at low frequency region and shear-thinning behavior compared to the undrawn samples. Additionally, the stretched samples demonstrated strain-hardening behavior at earlier times, at a given extensional rate, compared to the unstretched counterparts. Improvement of rheological properties was more pronounced for the drawn sc-PLA samples containing the branched and high-molecular weight PDLA. The drawn samples at 190 °C exhibited tiny spherical crystals in the range of 100-200 nm, whereas the relatively thin fibers in the size range of 60-70 nm were detected for the drawn blends at 230 °C. Finally, the batch foaming of the drawn samples at different processing temperature was conducted.