| Shear thickening fluid(STF)is a kind of non-Newtonian fluid,whose viscosity will increase dramatically when the shear rate(or shear stress)is larger than a critical shear rate.This behavior is reversible,the viscosity immediately decreases to the initial state when the shear rate(or shear stress)decreases.STF is composed of micron/nanoparticles uniformly dispersed in polar solvents.The early study about shear thickening(ST)behavior is to eliminate its negative influence in the process of industrial production.Due to the dramatic response to the shear rate,possessing the energy dissipation characteristic of liquid and high strength property of solid,STF has attracted considerable interests in the energy absorption,dampers and vibration control devices.Especially,the STF enhanced body armor prepared by STF combined with bulletproof fiber,which not only retained the soft and comfortable properties of the fiber,but also improved its bulletproof and impact resistance performance.The potential applications of STF are wide,however,there are still many problems to solve in the current research about STF.As for the influencing factors of ST behavior,previous studies mainly focus on the composition of system such as dispersed medium,dispersed phase types,additives and so on.The influence of the structure of dispersed phase particles on ST is rarely studied.Practical STF system is very limited,and it is urgent to develop practical and controllable STF system.Mechanical properties of ST behavior have always been the focus of research,and other characteristics of STF system are yet to be explored.The single impact protection performance of STF/Kevlar composite is far from enough to meet the needs of the next generation of smart wearable materials.STF fiber composites with sensing and other properties need to be developed.Therefore,the influence of the structure of dispersed phase particles on the properties of ST is studied firstly.Then,by studying the influence of different surface modification methods on ST performance,it is of great significance to develop STF with controllable performance.Then,a STF with non-iridescent structure color is developed to regulate the STF color by changing particle size,volume fraction of dispersed phase and temperature.Finally,a new type of CNT/STF/Kevlar wearable electronic textile sensor has been prepared,which has good protection and sensing performance.The specific content includes the following aspects:1.Preparation of SiO2@polydopamine(PDA)STF with core-shell structure and the relationship between ST properties and dispersed phase particle structure.Firstly,a facile method for synthesis of SiO2@polydopamine(PDA)nanoparticles with core-shell structure is developed.In the synthesis reaction,dopamine(DA)spontaneously polymerizes on the surface of SiO2 nanospheres to form a shell.The PDA shell thickness is regulated by changing the concentration of DA.The synthesized core-shell nanospheres are dispersed into polyethylene glycol 200(PEG 200)to obtain Si02@PDA based STF.Compared with pure SiO2 based STF,SiO2@PDA based STF exhibits better ST performance.Based on the experimental results,a mechanism of the relationship between ST properties and the structure of dispersed particles is proposed.2.Study the influence of different surface modification methods on ST performance and enhance the regulation of STF performance.A modified method for improving the performance of SiO2 based STF is developed.First,SiO2 nanospheres are modified with PVP K30 by ethanol reflux method to prepare STF(SiO2(PVP-STF).Compared with the unmodified SiO2-based STF,the ST effect of SiO2@PVP-STF increases significantly,the maximum viscosity increases by 7 times,and the critical shear rate decreases by about 10 times.Combined with the different effects of different modification methods on the rheological properties of STF,the possible mechanism of the relationship between ST performance and modification methods is proposed.It provides a new method to control ST behavior,which is helpful to understand the mechanism of ST effect.3.Develop colorful STF and explore the connection between the optical properties of STF and the properties of ST.A STF with non-iridescent structure color(defined as colorful STF,c-STF)is developed.The color of c-STF can be adjusted by changing particle size,dispersed phase volume fraction and temperature,and its color covers the entire visible spectrum.The color characteristics of c-STF are characterized by reflection spectrum and transmission spectrum.The internal microstructure of c-STF is observed by confocal microscopy.The relationships among structure transformation,color and rheological properties of c-STF are studied systematically.The test results show that the photonic band gap(PBG)is caused by the short-range ordered microstructure of c-STF.The color semi-transparent c-STF creates the possibility to observe the transformation of internal structure in the process of ST phenomenon through optical methods,which will be conducive to the further study of ST mechanism.At the same time,the adjustable color of STF also expands its application prospect.4.Preparation of wearable electronic fabrics and testing of their protective sensing performance.CNT is introduced into Kevlar impregnated with S TF to prepare a kind of wearable electronic textile(ET)composite material with excellent protective and sensing properties.In the puncture resistance experiments under quasi-static and dynamic impact conditions,ET composite can absorb more energy,and its protective performance is greatly improved than that of pure fiber.The maximum impact force of ET composite is up to 1232 N,much higher than that of pure Kevlar(746 N).With the addition of multi-walled carbon nanotubes(MCNT),ET composites have good conductivity.It can be used as a sensor to monitor various human movement signals under different conditions.ET composite has a good application potential in multi-functional wearable electronic textile products that need human protection and movement detection at the same time. |
PDF Full Text Request