Optimizing the ignition and combustion characteristics of Al by fluorine-containing oxidizers have attracted significant interest. However, few of them dedicated to alleviate the incomplete combustion of Al in propellant. Herein, we demonstrated that the combustion of micron-Al in AP free nitramine-based propellants can be greatly enhanced by thin coating layer of PVDF, resulting decreased volume fraction of agglomerates exceeding the initial particle size and active Al content in condensed combustion products (CCPs). After extensive analysis from thermal reactivity, single particle ignition and observation of particles evolution from burning surface to flame zone, we propose that the combustion efficiency is promoted by the fragmentation of chain structured aluminum skeleton by gas recoil near burning surface, oxidation acceleration by diffusion of Al and oxidative gas through the cracks among the particle shell in the dark zone and the subsequent ejection of molten Al triggered by gasification of low boiling point AlF 3 in the flame zone. The findings in this work suggest that core–shell Al@PVDF has a great potential to be further used in the development of future highly energetic solid propellants.
Selective separation is an effective method for the removal of heavy metal ions and waste oil from wastewater. Polyvinylidene fluoride (PVDF) was functionalized with polyvinyl acetate (PVAc) by in-situ polymerization, and novel PVAc-g-PVDF coating on surface modified cotton fabric were prepared. The contact angle (CA), pure water flux (PWF) and self-cleaning ability of coated cotton fabric were investigated in detail. In addition, the separation performance of coated cotton fabric was reflected by the removal of heavy metal ions in simulated wastewater. The results revealed that the PVAc-g-PVDF-coated cotton fabric was free of waste oil adhesion and was self-cleaning from waste oil in aqueous environment. Meanwhile, this coated cotton fabric can effectively separate oil/water mixtures with a high flux and high oil rejection, and was easily recycled for long-term use. More importantly, the heavy metal ions rejection ratio and adsorption capacity of cotton fabric were also improved with the addition of PVAc-g-PVDF coating. PVAc-g-PVDF-coated cotton fabric exhibited excellent rejection stability and reuse performances after several times fouling and washing tests. It can be expected that the present work will provide insight into a scaled-up fabrication process of PVAc-g-PVDF coating for purifying wastewater.
A flexible and stretchable three-dimensional nanocomposite membrane based on traditional cotton fabric is a promising alternative for proton exchange membrane because it has the capability of transferring protons, is inexpensive, and also have higher current density compared to Nafion membranes in microbial fuel cells. The obtained results showed that the highest power and current of PVAc-g-PVDF-coated cotton fabric were 400±10 mW/m 2 and 92 mA/m 2 , respectively. However, maximum generated power and current for Nafion-117 were 300±10 mW/m 2 and 60 mA/m 2 , respectively. The highest proton conductivity of PVAc-g-PVDF-coated cotton fabric was (1.5±0.2)×10 -2 S/cm at 25 °C and lowest glucose permeability was (12±1)×10 -6 cm 2 /s after Mg 2+ ions adsorption. Furthermore, the highest COD removal (85±3 %) and CE (11.2 %) were obtained from PVAc-g-PVDF-coated cotton fabric. The coated cotton fabric can provide a novel route for low-cost production of high-performance flexible proton exchange materials from the natural fabrics.
危险品化学品经营许可证（带存储）