Balancing processing ease with combustion performance in aluminum/PVDF energetic filaments

摘要

Molecular weight (M_w) effects in poly(vinylidene fluoride) (PVDF) influence both processability and combustion behavior in energetic AI-PVDF filaments. Results show decreased viscosity in unloaded and fuel-lean (i.e., 15 wt% Al) filaments. In highly loaded filaments (i.e., 30 wt% Al), reduced viscosity is minimal due to higher electrostatic interaction between Al particles and low M_w chains as confirmed by Fourier-transform infrared spectroscopy. Thermal and combustion analysis further corroborates this story as exothermic activity decreases in PVDF with smaller M_w chains. Differential scanning calorimetry and Thermogravimetric analysis show reduced reaction enthalpy and lower char yield in low M_w PVDF. Enthalpy reduction trends continued in nonequilibrium burn rate studies, which confirm that burn rate decreases in the presence of low M_w PVDF. Furthermore, powder X-ray patterns of post-burn products suggest that low M_w PVDF decomposition creates a diffusion barrier near the Al particle surface resulting in negligible AIF_3 formation in fuel-rich filaments.