双乳液法制备微孔球形药的孔结构形成机制

Formation Mechanism of Pore Structure of Ball Propellant with Micro-pores Made by Double Emulsion Method

为了揭示双乳液法制备微孔球形药孔结构的形成机制,分别在乳化、成球及溶剂蒸馏等过程中进行取样,并采用显微观察和图像分析方法探索了孔结构的形成和演变规律。结果表明:影响微孔球形药中孔结构形成的主要因素是乳化条件和溶剂蒸馏条件。硝化棉乳液中分散相水滴的形态及尺寸分布规律与成品微孔球形药中的孔结构及孔径分布规律基本一致。乳化条件决定球形药中孔的形貌特征;成球过程的工艺条件对孔径及孔的形貌无显著影响;溶剂蒸馏条件对孔径分布影响较大,溶剂蒸馏速度加快,孔隙发生聚集而导致孔径分布不均匀。通过降低溶剂蒸馏速度,成品颗粒中的孔结构均匀性可以得到有效改善。采用双乳液法制备的硝化棉基微孔球形药中的孔结构是由硝化棉乳液中的分散相液滴形态决定的。

The formation mechanism of pore structure of ball propellant with micro-pores made by double emulsion method is revealed. The formation and changing rule of pore structure are studied through sampiing, microscopic observation and image analysis during emulsifying, bailing and solvent distilling. The results show that the major parameters influencing the shape forming of pore structure are the conditions of emulsion and solvent distillation. The shape and size distribution of dispersed droplets in nitrocellulose emulsion are in basic agreement with the pore structure and pore size distribution in finished ball propellant. As a result, the pore morphology of ball propellant is determined by the emulsification conditions. The conditions of shape forming process have no significant effect on the size and morphology of the pores, while the solvent evaporation conditions have greater influence on the pore size distribution. The faster the solvent is distilled, the worse the pore structure uniformity is due to the agglomeration of pores. The pore structure uniformity of finished particles is improved effectively by reducing the speed of solvent distillation. The pore structure of nitrocellulose ball propellant with micro-pores made by double emulsion method is substantially determined by the morphology of the disperse phase droplets in nitrocellulose emulsion.