Duralthene armor is our prototype attempt to create a type of armor making use of a new element called Adamantium. Adamantium doesn't exist naturally. Rather, it is a derivative of an extremely rare element found occasionally in asteroids that have been recently struck by large comets.
Adamantium is the result of taking that rare material and subjecting it to an intense energy field. The result is a material that actually isn't completely in-sync with normal space. Duralthene armor is essentially taking the old Tri-Strontium alloy and coating it with trace amounts of this Adamantium material.
When a mass driver comes into contact with the Adamantium, the material of the mass driver is dissipated into the sub-dimensions of the Adamantium. It's difficult to explain but most of the mass is instantly moved out of our normal space and into a slightly out of sync dimension. The remaining material of the mass driver weapon is then absorbed through the traditional Tri-Strontium alloy.