Preparaiton And Properties Research Of Shear Thickening Fluid

With the intensification of global terrorism and the improvement of protective safetyconsciousness, personal safety has become an important problem for all mankind. In manycountries such as China, most of personal injuries are caused by daggers, knives and otherstabs as a result of strict control of guns. Therefore, the research on stab-resistant materialswith excellent performance is becoming a focus work. This paper mainly aims at thecontradictions of traditional stab-resistant materials between performance and flexibility, thecomplex of shear thickening fluid (STF) and traditional materials (Kevlar) is proposed toprepare the new type of flexible protective materials. In order to prepare the compositematerials with outstanding stab-resistant performance, this article focuses on rheologicalproperties and mechanisms of different STFs.This research aimed at the influence of molecular weight of dispersing medium, the typeof dispersed phase and the change of temperature for the shear thickening fluids. In this paper,STFs were prepared by different proportions of PEG200, PEG400and silica. The impact ofdifferent molecular weights of dispersing media for rheological properties of STF systemswas analyzed which picked out the basic STF system. On this basis, the morphology structureand density of the three kinds of dispersed phase, silica, graphenes (GNs) and carbonnanotube (CNTs), had been characterized and analyzed, as well as the rheological propertiesof STFs with these different dispersed phases. The mechanisms of STFs with multi-dispersedphase were firstly put forward in our research, and the rheological properties of the basic STFsystem and multi-dispersed phase STF system under different temperatures were studied.Finally, STF-Kevlar fabrics were prepared by impregnating different STFs, the quality,thickness and flexibility of the composites were analyzed. Quasi-static puncture-proofexperiment was carried out for pure fabric and STF-Kevlar to investigate the stab-resistantperformances and mechanisms.This paper firstly introduced the concept―complex‖to STF systems, which involvedmulti-dispersed phases and dispersing mediums in the preparation of STFs. The rheologicalexperiment results showed that, the overall viscosity of STFs with different molecular weightdispersing medium increased with the improvement of molecular weight, and the shearthickening behavior could take place earlier under the lower shear rate. Otherwise, GNs andCNTs played different roles in the STF system with multi-dispersed phases. It was shownthat adding suitable amount of GNs in the STFs with CNTs could decrease the viscosity andoptimize the rheological properties of system, which helped achieving the ideal shearthickening behavior. The models of STFs with dispersed phases were built for the first time inthis paper, and the mechanism had been explored preliminarily. In addition, the environmenttemperature also had influence on STF systems. With the increasing temperature, the overallviscosities of basic STF and multi-dispersed phases systems decreased and shear thickeningeffect got indistinctive.STFs with multi-dispersed phases and dispersing mediums were composited with theKevlar fabrics, the composites proved that the rheological properties of STFs had correlationwith the stab-resistant performance. At the same time, the experimental results also showed the load bearing of composite fabrics were improved by STFs, however, the additions of STFsalso resulted in the increasing weights of fabrics. After calculation on the promise without anyincrease in fabric weight, the stab-resistant performance of composites with two special STFsystems (basic STF system;1%GNs+2%GNTs system) could be enhanced.