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## Thermoreological properties of shear thickening fluids

### Monika Michalska

#### Abstract

Ceramic pose an integral part of the modern technology. It is applied in catalytic converters, solar cells or lasers industry [1]. New solutions provides innovational materials, such as shear thickening fluids (STF). These are the composite material based on ceramic powder and polymer agent, which exhibits higher viscosity during increasing shear rate, because of internal friction shear forces [2]. It is well known, that there are many parameters depend on rheological properties. It can be listed solid loading, shear stress, strain and temperature [3]. Shear thickening fluids are able to absorb impact energy This feature is used to designing protectors for the human body – in production of liquid armour for military and in impregnation of the sports guard [4]. However, impact energy absorbing by this material, is partially distracting. as a heat. It caused local raise of temperature, what is not favorable for protective properties The purpose of this work was investigate thermoreological properties of shear thickening fluids modified by solid particles characterized by different thermal conductivity: graphite and microspheres. Results and discussion Shear thickening fluids, were obtained by homogenization of submicron silica (KE-P10 and KE-P50) in poly(propylene glycol) of a molecular weight of 2000 g/mol (PPG 2000) and with the suitable amount of copolymer microspheres (DE20) or expanded graphite. The solid loading was in the range 50 or 52% by volume. In the preparation the dopants were used in range 0,1; 0,25 or 0,5%vol in relative to solid phase or whole STF. The rheological measurements were performed in 25; 36,6 and 50˚C. Cooling rate was also examined. Finally, thermal conductivity of selected samples was investigated. Conclusion Based on the results the impact of various factors on cooling rate can be determined. The solution of using dopants in order to acceleration heat dissipation was very effective. Expanded graphite advanced cooling process, and increased the thermal conductivity of samples relative to a reference sample. What is more, addition of the dopants improved shear thickening properties by increasing of dilatant effect. It was shown also, the dependence of the particle size of the solid phase on the cooling rate – smaller particles caused more efficient heat dissipation Furthermore, increase of dilatant effect was noticed by increasing solid loading. Copolymer microspheres did not change parameters of cooling process, because of insulating properties of gas inside them. It was also found, that the higher temperature negatively affected on shear thickening properties. However, it is possible to overcome the negative effect of weakening protective function during multiple hits by more efficient heat transfer obtained by addition of suitable dopants. The studies give an opportunity to further more comprehensive develop of the composition and preparation of the STF, in order to improve their thermorological properties, and increase their implementation
Diploma type
Engineer's / Bachelor of Science
Diploma type
Engineer's thesis
Author
Monika Michalska Monika Michalska,, Undefined Affiliation
Title in Polish
Właściwości termoreologiczne cieczy zagęszczanych ścinaniem
Supervisor
Mikołaj Szafran (FC/CChT) Mikołaj Szafran,, Chair of Chemical Technology (FC/CChT)Faculty of Chemistry (FC)
Certifying unit
Faculty of Chemistry (FC)
Affiliation unit
Chair of Chemical Technology (FC/CChT)
Study subject / specialization
, Technologia Chemiczna
Language
(pl) Polish
Status
Finished
Defense Date
04-02-2016
Issue date (year)
2016
Keywords in Polish
ciecz zagęszczana ścinaniem, przewodność cieplna, reologia, szybkość chłodzenia
Keywords in English
shear thickening fluids, viscosity, thermal conductivity,
Abstract in Polish
urn:pw-repo:WUT5ec744ad88034b4f9419578e14ac42b8