调控聚氨酯聚集态结构制备高性能介电弹性体

Preparation of High Performance Dielectric Elastomers by Tailoring the Aggregation Structure of Polyurethane

通过退火保温调控聚氨酯(TPU)的相结构、结晶结构和氢键结构,进而调控其模量和介电常数(ε'),提高TPU的电驱动性能.使用扫描电子显微镜(SEM)和小角X射线(SAXS)研究TPU的结晶结构,基于红外光谱对TPU的氢键变化进行半定量分析,使用原子力显微镜(AFM)研究TPU的微相分离结构.结果显示,退火温度和时间不同导致TPU的聚集态结构各异,对模量、ε'和电驱动性能产生了较为复杂的影响.低温(80℃)退火处理后,硬相分布于连续的软段相,且形成了较多软段结晶,相分离程度和氢键破坏程度提高.相比于高温(150℃)退火处理,低温退火后获得较高ε'的同时保持了较低的模量,从而产生较大电致形变.值得注意的是,低温退火条件下产生大范围的软段结晶,使得软段分子链之间排布紧密,导致TPU电击穿强度大幅度提升,得到具有高击穿强度、高电致形变的TPU介电弹性体材料.80℃退火处理6 h后,TPU的电击穿强度从退火处理前的25 kV/mm提高至32 kV/mm,最大电致形变从0.77%提高至3.3%,提高4.3倍.

The phase structure,crystallization and hydrogen bonding of thermal polyurethane(TPU)were controlled by annealing process.And the modulus and dielectric constant(ε')of TPU were tailored to improve the electromechanical properties of TPU.Scanning electron microscopy(SEM)and small angle X-ray(SAXS)were used to study the crystalline structure of TPU.The changes of hydrogen bonding of TPU were semi-quantitatively analyzed by infrared spectroscopy.The microphase separation structure of TPU was studied by atomic force microscope(AFM).The results show that changing annealing temperature and time results in complex aggregation structures,thus leading to very different electromechanical properties.After annealing at 80℃,large numbers of soft segment crystals were formed with the hard phase distributing in the continuous soft phase.Both phase separation and the destruction of hydrogen bonding were improved compared with those of 150℃annealing treatment.Therefore,higherε'and lower modulus were obtained,resulting in larger actuated strain.Besides,under the condition of low temperature annealing,a wide range of soft segment crystals were produced,which makes the molecular chains of soft segments closely arranged,resulting in a significant increase in the breakdown strength of TPU.The results show that after annealing at 80℃for 6 h,the electrical breakdown strength of TPU increases from 25 kV/mm to 32 kV/mm,and the maximum actuated strain increases from 0.77%to 3.3%,increased by 4.3 times.