Enhancing combustion performance of aluminum-water gelled propellants via polyvinylidene fluoride

Aluminum–water (Al-H₂O) propellants represent an innovative class of solid propellants characterized by low cost and minimal signal signature. However, conventional formulations are hindered by significant aluminum (Al) agglomeration, leading to reduced combustion efficiency and substantial residues. This study introduces a method for modifying Al powder with Polyvinylidene Fluoride (PVDF) to enhance the performance of Al-H₂O propellants by mitigating agglomeration during combustion. Experimental methodologies, including thermogravimetric analysis under ambient-pressure nitrogen atmosphere and laser ignition tests, were employed to investigate the influence of varying PVDF content on the combustion characteristics of the propellants. Furthermore, the effect of PVDF on motor performance was systematically evaluated through laboratory-scale Solid Rocket Motor (SRM) tests. The results demonstrate that the addition of 7.5 % PVDF significantly enhances the burning rate from 1.12 mm/s to 3.78 mm/s and reduces the mean particle size of condensed combustion products from 699 μm to 527 μm. Combustion efficiency rises from 88.57 % to 94.51 %, while injection efficiency improves significantly from 30.45 % to 70.45 %. SRM tests further demonstrate an increase in combustion chamber pressure from 0.17 MPa to 0.58 MPa. A dynamic agglomeration model explains these improvements, attributing reduced agglomeration to enhanced aerodynamic forces and a thinner melting layer, while increased gas yield improves injection performance. This study highlights PVDF's potential in advancing Al-H₂O propellants by improving combustion and injection efficiency.