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Open AccessArticle

The Effect of Thermal History on the Fast Crystallization of Poly(l-Lactide) with Soluble-Type Nucleators and Shear Flow

The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, 1800 Lihu Road, Wuxi 214122, China
Author to whom correspondence should be addressed.
Academic Editors: Alexander Böker and Frank Wiesbrock
Polymers 2016, 8(12), 431;
Received: 14 October 2016 / Revised: 24 November 2016 / Accepted: 1 December 2016 / Published: 10 December 2016
(This article belongs to the Special Issue Young Talents in Polymer Science)
The N1,N1ʹ-(ethane-1,2-diyl)bis(N2-phenyloxalamide) (OXA) is a soluble-type nucleator with a dissolving temperature of 230 °C in poly(l-lactic acid) (PLLA) matrix. The effect of thermal history and shear flow on the crystallization behavior of the PLLA/OXA samples was investigated by rheometry, polarized optical microscopy (POM), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and scanning electron microscopy (SEM). The crystallization process of the PLLA/OXA-240 sample (i.e., pre-melted at 240 °C) was significantly promoted by applying a shear flow, e.g., the onset crystallization time (tonset) of the PLLA at 155 °C was reduced from 1600 to 200 s after shearing at 0.4 rad/s for even as short as 1.0 s, while the crystallinity (Xc) was increased to 40%. Moreover, the tonset of the PLLA/OXA-240 sample is 60%–80% lower than that of the PLLA/OXA-200 sample (i.e., pre-melted at 200 °C) with a total shear angle of 2 rad, indicating a much higher crystallization rate of the PLLA/OXA-240 sample. A better organization and uniformity of OXA fibrils can be obtained due to a complete pre-dissolution in the PLLA matrix followed by shear and oscillation treatments. The well dispersed OXA fibrils and flow-induced chain orientation are mainly responsible for the fast crystallization of the PLLA/OXA-240 samples. In addition, the shear flow created some disordered α′-form crystals in the PLLA/OXA samples regardless of the thermal history (200 or 240 °C). View Full-Text
Keywords: poly (l-lactide); crystallization; soluble-type nucleator; shear flow; melting process poly (l-lactide); crystallization; soluble-type nucleator; shear flow; melting process
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Shen, T.; Ma, P.; Yu, Q.; Dong, W.; Chen, M. The Effect of Thermal History on the Fast Crystallization of Poly(l-Lactide) with Soluble-Type Nucleators and Shear Flow. Polymers 2016, 8, 431.

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