Synthesis of Novel Organic Urea Compounds and Their Roles as Crystallization Nucleating Agents of Poly (L-lactic acid)
writer：Yutao Xu, Linbo Wu*
keywords：Poly(L-lactic acid), Biodegradable polymers, Crystallization, Nucleating agents, Bisurea compounds
source：期刊
specific source：European Polymer Journal , 49(4): 865-872, (2013)
Issue time：2013年
A series of novel organic bisurea (BUr) compounds were facilely synthesized from phenyl
isocyanate and a variety of diamines, and their roles as crystallization nucleating agents of
commercial poly(L-lactic acid) (PLLA) were investigated through differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction
(WAXD). Their crystallization accelerating efficiency depends on the methylene numbers
in molecular structure: the less the CH2 number, the faster the crystallization rate. Among
them, 1,10-(ethane-1,2-diyl)bis(3-phenylurea) (BUr1) acts as the most effective crystallization accelerating agent. In the presence of ca. 2 wt% BUr1, the melt crystallization enthalpy of PLLA increases from almost 0 to 31.2 J/g under cooling rate of 10 C/min, and the isothermal
melt crystallization rate increased by 10.5 times at 140 C. Much higher nucleation density and smaller spherulite size of PLLA were observed by POM, indicating obvious heterogeneous nucleation effect. And the crystal structure of PLLA remains unchanged after incorporation of the nucleator.