Research on rheological properties of two types of nitromethane gelled propellants

The nitromethane(NM) gels were prepared by using fumed silica(SiO₂) and carboxymethyl cellulose nitrate(CMCN) as gelled propellant, respectively. The formation mechanism of two types of gels and the difference of rheological properties between NM/SiO₂ and NM/CMCN gels caused by the gel type were investigated. The yield stress, thixotropy, creep and thermosensitivity of two types of gels were investigated by linear rheological methods. The flow data and creep data of gels were fitted by using Power-Law model, Herschel-Bulkley model and Burger model, respectively. The experimental results show that NM/SiO₂ gel is a kind of accumulation gel agglomerated with small molecular aggregates formed by SiO₂ particles with hydrogen bonds, while NM/CMCN propegel is a physical gel with a crosslinking network structure which is formed by non-covalent interaction of hydrophobic bonds and interchain hydrogen bonds between amphiphilic group along the macromolecular chain of CMCN and small organic molecules. The non-Newton coefficient n of two types of gels are all less than 0.60. Compared with NM/CMCN gel, NM/SiO₂ gel has higher yield stress, shear thinning, elastic compliance and elastic responsivity, and lower thixotropy recovery and internal friction. The gel strength of NM/SiO₂ is become stronger at higher temperature and lower temperature.