Polymorphic microstructure of MDI/BD-block polyurethane as determined by temperature-sensitive conformation variation
Polymorphic microstructure of MDI/BD-block polyurethane as determined by temperature-sensitive conformation variation
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由温度敏感构象变化确定的 MDI/BD 嵌段聚氨酯的多晶型微观结构
DOI：
10.1039/d1sm01283e
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发表时间：
2021
期刊：
影响因子：
3.4
通讯作者：
Wang Zongbao
中科院分区：
文献类型：
--
作者：
Wang Zeyu;Li Xuke;Poeselt Elmar;Eling Berend;Liao Tao;Wang Zongbao
采用多种技术研究了MDI/ bd嵌段热塑性聚氨酯（tpu）在不同等温温度和不同冷却速率下的结晶。当等温温度等于或高于150℃时，MDI/BD块体以II型结晶，在较低的等温温度下以I型结晶。晶型II的晶体弹性模量为6.75 GPa，高于晶型I的1.31 GPa。从结晶状态下的c轴长度来看，形式I表现为收缩构象，而形式II表现为扩展构象。基于红外光谱的二阶导数分析和简单的建模，认为构象差异源于氨基甲酸乙酯基团在苯基环上的内键旋转和苯基- ch2 -苯基的开键角。在150℃以上生成形式II可能是由于氨基甲酸乙酯和柔性亚甲基在高温下的活化。综上所述，MDI/BD区块的结晶过程涉及到物理化学变化。
MDI/BD-block thermoplastic polyurethanes (TPUs) crystallized at different isothermal temperatures and different cooling rates were investigated using multiple techniques. The MDI/BD blocks crystallized in form II when the isothermal temperature was equal to or higher than 150 °C, and in form I at lower isothermal temperatures. Form II had a higher crystal elastic modulus of 6.75 GPa than form I of 1.31 GPa. Form I exhibited contracted conformation, while form II exhibited an extended conformation when viewed from the length of the c-axis in the crystalline state. Based on an analysis of the second derivative in FTIR spectroscopy and simple modeling, the conformation differences were considered to stem from the urethane group's internal bond rotation concerning the phenyl ring and the opening bond angle of phenyl-CH2-phenyl. The generation of form II above 150 °C may be due to the activation of urethane and the flexible methylene elevated by the high temperature. Overall, it was seen that the crystallization of MDI/BD blocks involved a physicochemical change.