Surface Modification of High Loaded Plastic Bonded Explosive Interfaces Modified via Biologically Inspired Core-Shell Coating Technique*

Plastic-bonded explosives (PBX) are polymer matrix composites that are highly loaded with micron-scale explosive crystals. A limiting mechanical factor in a PBX is the interface between the polymer binder system and the crystalline explosive. Synthetic dopamine, capable of undergoing self-polymerization under ambient conditions and becoming polydopamine (PDA), has been demonstrated to form controllable nanometer thickness films which has been shown to promote the adhesion between the filler and binder system. These films are thought to create a core-shell architecture, consisting of a rigid polymer shell over the substrate. PDA film structure and growth must be better understood before it can be applied in general use with high explosive (HE) materials. Neutron reflectometry (NR), performed on the Asterix beam line at the Los Alamos Neutron Science Center, has been employed to demonstrate the controllable nature of PDA film growth and the film's structure. From the NR experiments, a material model PDA was constructed to fully explain the structure of PDA and how its controlled growth can be used to modify surface structure and therefor adhesion. Both atomic force microscopy and bulge disk adhesion testing were used to demonstrate control of the surface modification.