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