Influence of Dispersion Methods on the Mechanical, Thermal and Rheological Properties of HTPB-based Nanocomposites: Possible Binders for Composite Propellants

Kavita Ghosh, Arvind Kumar, Shaibal Banerjee, Uma Sankar Patro, Manoj Gupta
2019 Central European Journal of Energetic Materials  
The present study reports on the methods of preparation for HTPBclay nanocomposites and their mechanical, thermal and rheological properties for their functional utility as an improved binder system for composite propellants. HTPB-clay nanocomposites were prepared by dispersing organoclay Cloisite 30B (1-3 wt.%) in the polymer matrix by magnetic stirring and high shear mixing. Critical parameters like time, temperature and RPM were optimized. These nanocomposites were cured with toluene
more » ... ith toluene diisocyanate in the presence of the cure catalyst DBTDL. The dispersion of the nanoclay was evaluated by using small angle X-ray scattering (SAXS) and energy dispersive X-ray (EDX) spectroscopy. EDX suggested homogeneous distribution while SAXS revealed partial exfoliation of the clay particles in the polymer matrix. Superior dispersion of the nanoclay was obtained by high shear mixing. The tensile properties of the nanocomposites prepared by high shear mixing showed 10-20% more strength and elastic modulus. The nanocomposites showed thermal stability higher than the pristine HTPB. Swelling behavior revealed increased cross linking, and the rheological behavior exhibited higher viscosity of the nanocomposites. In addition, the clay amount was increased up to 10 wt.% and its effect on the mechanical, thermal and swelling behavior was observed. Theoretical performance predictions of composite propellants with nanocomposites revealed their possible functional utility. Critical parameters like time, temperature and RPM were optimized for both techniques. Initially, in order to establish the method of dispersion, samples were prepared by using only up to 3 wt.% of nanoclay. These samples were characterized by SAXS and EDX analysis, and revealed that high shear mixing is a better technique for uniform dispersion. Hence, this technique was further used to prepare and study the effect of clay content on the mechanical and thermal properties of nanocomposites by using up to 10 wt.% of nanoclay. The swelling and rheological behavior of these composites was also determined and found satisfactory for their functional utility and processing. The tensile properties of these nanocomposites showed a substantial improvement with up to 7 wt.% of nanoclay incorporation, but, beyond this level the tensile strength decreased significantly and the nanocomposites lost their mechanical strength. This demonstrates that, there is an optimum percentage of nanoclay for a particular polymer system, where the improvement in tensile properties will be maximized.
doi:10.22211/cejem/109719 fatcat:75n6yd63a5hwxjj4tggn65jerq