COATING SIMULANT OF NITRAMINE BASED PARTICLES WITH UV CURABLE COMPOSITIONS IN A FLUIDIZED BED

摘要

Coating particles with polymeric materials is a widely used technique to tailor particle properties and provide add-on values. For energetic particles, various coating materials have been used to provide specific functional properties, such as IM, barrier, frictional and binder compatibility. In the current study, a novel technology to coat simulant of nitramine based particles with UV curable compositions in a fluidized bed processor has been developed. Since liquid UV curable compositions can be converted to solid materials almost instantaneously under UV light, the UV chemical-fluidized bed particle coating technology enables the complete de-coupling of the particle flow from the chemical curing/solidification steps. This greatly reduces the required coating process time and minimizes undesirable particle agglomeration and attrition. Fast curing, environmental benign and low operating temperature make this new developed particle coating technology especially suitable for the heat-sensitive energetic materials. Furthermore, this coating technique is applicable to both non-water soluble and water soluble core materials. It could be used in the functional coatings of water sensitive materials such as Mg particles. In this study, a pilot-scale explosion-proof Wurster fluidized bed/UV lamp system is designed, fabricated and integrated. A multi-spraying and curing protocol has also been developed and incorporated into the coating process. Based on the results from the Scanning Electron Microscope (SEM) analysis, Ash Test and Release Test, it is found that the coating performance related properties such as the coating thickness and degree of coverage are dependent on the operating variables including the total amount and the feeding protocol of UV chemicals, UV light exposure time, atomization and the fluidization conditions. The properties of coating layer can be readily tailored by the UV chemical formulation and the coating/curing conditions.