<title>Development of particle standards for testing explosive detection systems: characterization of the adhesion forces between composition 4 particles and polyethylene</title>

Abstract

A method has been developed to study the adhesion of particles on a surface and the gas velocity needed to overcome the adhesion and dislodge the particle from the surface. Experiments have been performed to determine the minimum detachment velocity for particles deposited on a surface by gravitational settling and by finger print transfer. Particles of Arizona road dust and SiO<SUB>2</SUB> were deposited on smooth, and frosted glass for the study. In addition, composition-4 particles transferred via finger print onto polyethylene films were also studied. Results indicate that gas velocities in the 1 - 100 m/s range were needed to detach particles in the 10 - 300 micrometers range from these surfaces. Generally, the larger the particle size, the lower is the detachment velocity. Particles transferred via finger print were found to adhere to surfaces more tightly than similar particles deposited by gravitational settling, and surface roughness tend to decrease the detachment velocity.