Study On Dynamic Mechanical Properties Of Polyborosiloxane Modified Silica Gel And Foamed Polyurethane

Polyborosiloxane(PBDMS)is a polymeric smart material with shear thickening properties This material exhibits flow dynamics properties at low strain rates and solid properties when th material is under impact of force.By absorbing impact energy,PBDMS performs impact resistance and buffer energy absorption properties.In this paper,PBDMS was prepared by using boric acid and hydroxy silicone oil.We analyzed the rheological properties of PBDMS and the relationship between the density of boride crosslinking and the hydroxyl content of hvdroxv si icone oil.At the same time,this research uses PBDMS modified two-component liquid silica gel to analyze th mechanics,buffer energy absorption effect,impact resistance of modified silica gel,also relationship between modified gel and the boronization crosslink density,hydorxyl silicone oil content,and silica particle filling amount respectively.The foamed polyurethane was modified by PBDMS to analyze the dynamic mechanical properties and buffer energy absorption effect of the modified foamed polyurethane.Research results indicate that:(1)The viscosity of PBDMS increases with the increase of shear rate,and PBDMS has a shear thickening effect.At the same time,with the increase of hydroxyl content of PDMS and the increase of boronization crosslink density,the critical viscosity value of shear thickening will increase,and the shear thickeninrg effect will be more significant.The boronization crosslink density has a certain saturation value.When the boronation crosslink density of PBDMS reaches saturation state,the shear thickening effect of PBDMS also tends to be saturated.Only when the ratio of hydroxyl silicone oil(8.5%)to boric aci reaches 1:3,can PBDMS owns the strongest shear thickening effect.(2)With increasing hydroxyl content and density of crosslinking of raw PBDMS modified silica gel will show larger loss modulus and storage modulus.Meanwhile,the ability to consume energy increases while the ability to rebound after deformation becomes stronger.The better the dynamic mechanical properties of PBDMS is,the higher resilience performance and damping capacity will be.Buffer energy absorption effect of silica gel can be improved the modification of PBDMS and the improvement is consistent with dynamic mechanical properties.Which is that more hydroxyl content is,higher the boronization crosslink density,and the more buffer energy absorption of the material will be.According to our results,the buffered energy absorption effect of PBDMS modified liquid silica prepared by the ratio of PDMS to boric acid of 1:8.5 with hydroxyl content of 8.5%was the best.(3)For PBDMS modified silica gel,higher filling amount of silica particles would increase the loss modulus as well as storage modulus of the material,also this will improve the dynamic mechanical properties of the material with a certain saturation value.When the filling amount of silica particles go beyond the saturation value,the filler will affect the cross-linking of the silica gel reaction.When the silica particle content increases to 8%,the filling amount of the material is basically saturated,and the dynamic mechanical properties under this circumstance are optimal.The silica gel after PBDMS modification has better impact resistance and higher strength than pure silica gel.Within a certain range,the higher strain rate of impact is,the more obvious the impact resistance of PBDMS on silica gel will be,also,the PBDMS silica gel will show strain rate sensitivity effect.As the content of silica particles increase,the impact resistance of PBDMS modified silica gel will also increase until the filling amount is saturated,and the optimum filling amount is 8%.(4)The PBDMS modified foamed polyurethane will show a decrease in hardness while the buffer energy absorption effect of PBDMS modified foamed polyurethane is stronger than that of pure foamed polyurethane.PBDMS modification can improve the dynamic mechanical properties of foamed polyurethane,so that the material can obtain better elasticity under stress and has better ability to consume deformation energy,so to say higher storage modulus and loss mode.The dynamic mechanical properties of the material are more significant improved under high frequencies.