Research On The Fabrication And Performance Of Bacterial Cellulose-Based Flexible Protective Material

Shear Thickening Fluid is a kind of flexible protective material with high fluidity at low shear rate and hardening characteristics at high shear rate,which has advantages in the field of impact protection.According to the two current shear thickening systems（Colloidal particle system Shear Thickening Fluid（STF）and non-brownian particle system Shear Thickening Fluid（DSTF））,In this article,we prepared STF with SiO₂ as the dispersed phase,PEG as the dispersed medium and prepared DSTF with starch particles as the dispersed phase and pure water or cesium chloride solution as the dispersed medium.Combined with the relevant advantages of our research group on BC materials,we prepared STF-BC and BC-DSTF composites respectively.The dispersed phase particles were characterized by SEM,TEM,XRD and DLS.The rheological properties of shear thickening system were characterized by rheometer.The STF-BC composite’s anti-prick ability was tested by self-made drop hammer.A self-designed ballistic launch system was used to characterize the macroscopic protection performance of BC-DSTF.The specific work includes the following aspects:（1）The STF Shear Thickening Fluid was prepared by combination of mechanical agitation and ultrasonic,the preparation process was optimized combining the analysis results of DLS.The rheological properties of STF were characterized by MCR302 rheometer:the larger the mass fraction of the dispersed phase,the stronger the shear thickening effect;the longer the molecular chain of the dispersed medium,and the stronger the shear thickening effect（PEG600>PEG400>PEG200）.On this basis,combined with the actual temperature,the preparation parameters of STF shear thickening solution（dispersion medium:PEG400,mass fraction of dispersed phase:28wt%）were determined.The rheological results showed that STF prepared on this parameters not only had excellent shear thickening performance,but also had excellent stability and invertibility,and the shear thickening viscosity was up to 50Pa·s.（2）We developed an in situ regulation method to prepare BC films with average pore diameter of 30 microns by adding Ca-alginate template as porogens,and porous BC films were impregnated to STF to obtain STF-BC composites.STF-BC was characterized by anti-stinging performance by drop hammer machine.The results showed that,compared with STF-Kelvar materials,STF-BC possessed 69%of STF,much higher than 11%of STF-Kelvar;STF-BC is much more flexible,bending Angle is 85°much higher than STF-Kelvar 45°;STF-BC has excellent anti-stinging performance,when the drop hammer kinetic energy is 8J,6.11mm STF-BC has better anti-stinging ability than 5.76mm STF-Kelvar.（3）Based on the study of mechanism of"Jamming",DSTF Shear Thickening Fluid may happen"Jamming"behavior under the action of shear,and the friction between the dispersed phase particles directly affect the"Jamming"behavior and strength.On this basis,in the idea of enhance the friction between the dispersed phase particles,we added BC/SiO₂ coarse fibers to DSTF to prepare BC-DSTF composite material,using MCR302 rheometer to test DSTF and BC-DSTF shear thickening fluid rheological properties,the results showed that:because of the addition of coarse fiber,relative to the DSTF,BC-DSTF’s critical shear rate?_c sharp decline,and the shear thickening viscosityη_jamam greatly increased.The ballistic launch system with a kinetic energy of 90J was designed and customized,and the macro-protection performance tests of DSTF and BC-DSTF were carried out by this system.The results showed that:forΦ=43%DSTF and BC-DSTF,5cm thick BC-DSTF can reach 9cm thick DSTF protective effect,when dealing with the impact energy of 90J,and 5cm thick BC-DSTF Shear Thickening Fluid can reduce the pressure to the safety range of the human body,the ballistic test results showed that the BC-DSTF composite material has great potential applications in the field of individual protection.