RESUMEN
The study focuses on the effect of thermal deformation degree of polyacrylonitrile (PAN) particles on the electrorheological (ER) properties of their suspensions. The heat-treated PAN particles are manufactured as ER materials using a thermocatalytic processes. The molecular structures of ER materials are analyzed to confirm a stabilization or a carbonization degree. We categorized the prepared ER particles into three basic types according to their deformation degree: Thermal dried PAN, stabilized PAN, and pre-carbonized PAN. The raw, stabilized, and pre-carbonized PAN particle-dispersed suspensions showed positive ER properties. The ER properties are enhanced as the heat-treatment temperature increases due to improved dielectric property. However, the thermal dried PAN particle ER suspensions showed negative ER behavior though the particles have higher conductivity and dielectric constants than those of the host fluid, which is contrary to the conduction model. XRD results indicate that the ER materials could show contradictory ER behavior even if they have the same molecular structures due to their crystallinity. This discovery is expected to boost the development of both positive ER and negative ER suspensions based on carbonaceous ER materials.
RESUMEN
Herein, the mixing effect of amine and carboxyl groups on electrorheological (ER) properties has been presented with the chitosan and alginic acid dispersed suspensions. Chitosan (for the amine group) and alginic acid (for the carboxyl group) are used to investigate the mixing effect of the amine and carboxyl groups on ER properties with the control of their mixing ratio in the silicone oil. The surface-chemical structure of the mixture of the chitosan and alginic acid particles in the silicone oil is demonstrated by in situ Fourier transform infrared (FT-IR) spectroscopy at various electric fields for the first time. This study focuses on whether the mixture of chemical groups in the ER fluid can promote ER properties or not, and in situ FT-IR analysis of the interface between ER particles in the silicone oil at various DC electric fields. The ER fluids exhibited the increase of the yield stress values with the increase of the counter group addition up to the weight ratio of 50 : 50 (chitosan : alginic acid). A noteworthy result is that the mixing effect of the amine and carboxyl groups resulting in enhanced ER properties is clearly proved. In the in situ FT-IR study, the complex form of amine and carboxyl groups of particles in the ER fluid was confirmed under the electric field.
RESUMEN
Herein, the effect of the degree of deacetylation (DD) on the gelation of the chitosan dispersed suspension as an electrorheological (ER) fluid under an electric field is presented. The fluids were prepared by dispersing the chitin and the chitosan particles having various DDs into silicone oil, and they were evaluated under various electric fields. The alignment of chitosan particles in the fluid was also observed using an optical microscope under the electric field. The formed fibrous structure between electrodes are though to continue to the viscosity increase, because an attempt to move one electrode relative to the order would be hindered by the drag of the dangling fibrils. A noteworthy result is that the region of the frequency for gel state of the ER fluids increased in the order of chitosan DD 99.3, 93.4, 73.2, 83.8, and 87.3% under electric fields while the modulus of the fluids increased in the reverse order. This order was well-matched with the result of dielectric constants and yield stresses of ER fluids. The study of influence of DD on the gelation of the chitosan dispersed suspension under an electric field shows the relevance of the chemical composition of the heteropolysaccharide (chitin-chitosan copolymer) to the rheological and electric properties of ER suspensions.