压力下软段含量对聚氨酯材料动态力学性能的影响

Effects of soft segment content on dynamic mechanical properties of polyurethane materials under pressure

聚氨酯材料内部存在特有的微相分离结构,受到外力作用时其链段及分子之间会发生相对运动,产生内摩擦,消耗能量,为材料提供阻尼特性。而在水下环境中,静水压力会导致材料表现出与常压不同的动态力学特性,从而影响材料的阻尼性能。针对这一问题,通过两步法工艺合成不同软段含量的聚氨酯材料,对其进行了一系列的结构与热性能表征,同时,通过施加0.5 MPa的预应力进行了常规的压缩力学性能测试与压缩模式下的动态热机械分析,表征材料在压力环境下的静态与动态力学性能。结果表明,软段含量的增加会对聚氨酯的玻璃化转变温度和压缩强度产生规律性的下降影响,同时降低了聚氨酯材料在变温模式下的储能模量参数,而损耗因子的峰值呈现规律性增大,证明了软段含量的增加加强了压力下聚氨酯材料对温度的响应;变频模式下软段含量的增加与变温模式下的变化规律相吻合,即软段含量的增加同样加强了压力下聚氨酯材料对频率的响应,这些规律的揭示为探究压力下不同软段含量聚氨酯材料的温度和频率响应特性,以及为水压下高耗能聚氨酯材料设计提供了有效的理论依据。

There is a unique microphase separation structure in polyurethane material,when polyurethane materials are subjected to external forces,relative motion occurs between the chain segments and molecule,producing internal friction and dissi-pating energy,thus providing damping characteristics to the material.In an underwater environment,the hydrostatic pressure alters the material's dynamic mechanical properties compared to those at atmospheric pressure,affecting its damping performance.Addressing this issue,polyurethane materials with varying contents of soft segments were synthesized using a two-step process.A series of structural and thermal characterizations for the materials were done.Additionally,by applying a pre-stress of 0.5 MPa,conventional compressive mechanical tests and dynamic mechanical analysis under compression were conducted to characterize the static and dynamic mechanical properties of the material under pressure.It is found that increasing the content of soft segments systematically lowers the glass transition temperature and compressive strength of the polyurethane materials,and reduces the storage modulus parameters in temperature-sweep mode,with a regular increase in the peak values of the loss factor,proving that a higher content of soft segments enhances the temperature responsiveness of polyurethane under pressure.Similarly,in frequency�sweep mode,the increase of soft segments content corresponds with the changes observed in temperature-sweep mode,indicating that a higher content of soft segments also enhances the frequency responsiveness of polyurethane under pressure.These findings provide insights into the study for temperature and frequency response characteristics of polyurethane materials with different soft segment contents under pressure,serving as a basis for the design of high-energy-dissipating polyurethane materials for use in hydro-static environments.