Achieving highly crystalline rate and crystallinity in Poly(l-lactide) via in-situ melting reaction with diisocyanate and benzohydrazine to form nucleating agents. (January 2020)

• Record Type: Journal Article
• Authors: Liu, Ji-Hong; Cai, Jie-Hua; Tang, Xiao-Hong; Weng, Yun-Xuan; Wang, Ming
• Is Part Of: Polymer testing. Volume 81(2020)
• Publication Date: 2020-01
• Subjects: Poly(l-lactide) -- Nucleating agent -- Crystallinity -- Heat resistance; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2019.106216
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: The drawback of the application for poly(l -lactide) (PLLA) is the low crystalline rate and crystallinity obtaining via normal processing methods. Modifying crystallization of PLLA has been found to be an efficient way to improve its mechanical and heat resistance properties. In this wok, 4, 4′-diphenylmethane diisocyanate (M) and benzohydrazine (P) were employed into PLLA melt to in-situ form nucleating agents. The in-situ melting reaction was confirmed by a nuclear magnetic resonance spectroscopy. The crystallization behavior and crystalline morphology were investigated by a differential scanning calorimetry, a polarized optical microscopy and a field emission scanning electron microscope. The crystalline rate of PLLA was abruptly enhanced by adding (M+P) and melting reaction with PLLA. The crystallization half-time of PLLA dramatically decreased from 42.0 to 1.1 min at 130 °C by the in-situ formation of nucleating agents. The crystallinity of PLLA increased from 10.3 to 42.1 by adding 0.25% (M+P) and melting reaction for 8 min. Furthermore, the size of PLLA crystals was dramatically reduced because of the nucleating effect. Accompanied with improvement on crystallinity, the Vicat softening temperature of PLLA shifted from 57.4 °C to 93.7 °C by the in-situ reaction with 6.00% (M+P), and indicating heat resistance enhancement. Highlights: High crystallinity was achieved in PLLA via the in-situ melting reaction. The in-situ modified PLLA exhibited high crystallization rate. Heat resistance performance of PLLA was greatly improved by the modification. High-efficient nucleating agents were formed in PLLA by the in-situ reaction. The in-situ modified PLLA was more toughness than that of neat PLLA.