Thixotropic gels of unsymmetrical dimethyl hydrazine (UDMH) have been prepared using methyl cellulose (4.48 wt%) and agar‐agar (0.64 wt%) chemical gelling agents. Red fuming nitric acid has been gelled by using sodium silicate (4.25 wt%).
The effect of various parameters like size of container, particle size of gellants and temperature on gellation time of UDMH gelled system has been investigated. The gellation time of UDMH gel is found to increase with the increase in the internal diameter of the container. Gellation time is found to show direct proportionality with the particle size when methyl cellulose is used as gellant. In case of methyl cellulose, the gellation occurs quickly at higher temperature whereas the reverse trend is observed when agar‐agar gellant is used.
In order to boost the performance of liquid propellants, the metallized gels of UDMH containing Al (10‐40 wt%) and Mg (10‐25 wt%) metal powders have been prepared. The density measurements of virgin and metallized gels reveal that there is a maximum gain of 46.72% and 19.3% over virgin gels on incorporation of Al and Mg powders respectively.
Efforts have been made to understand the process of gellation using optical and photomicrographic techniques.
Rheological studies on unsymmetrical dimethyl hydrazine‐methyl cellulose gelled system have been conducted under varying shear rates in order to establish its flow characteristics. The gel is found to behave as a pseudoplastic thixotrop. The viscosity build‐up with respect to time has been traced till apparently a firm gel is set. The viscosity is found to increase with time rapidly in the beginning and minor changes are observed thereafter. The effect of temperature and extent of metal (Al and Mg) loading on apparent viscosity of the gelled system has also been investigated. Both the apparent viscosity and thixotropic character of the virgin gel are found to decrease with increase in temperature. An increase in rate of shear decreases the apparent viscosity significantly. The thixotropic character of the metallized gelled systems is observed to increase with metal content and that they exhibit a shearthinning behaviour too. Power law has been applied to assess the variation of pseudoplastic index n and consistency index K with temperature and metallization. The results reveal that n increases with temperature and decreases with metal loading whereas K shows an opposite trend. The yield value of gelled systems is noted to show decrease with temperature and increase with metal incorporation.
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