Powder Diffraction

Technical Articles

Investigation of microstructural changes in impacted polyurea coatings using small angle X-ray scattering (SAXS)

Edward Balizera1, Jeffry Fedderlya1, Gilbert Leea1, Susan Bartyczaka2 and Willis Mock Jr.a2

a1 Naval Surface Warfare Center, Carderock Division, Bethesda, Maryland 20817

a2 Naval Surface Warfare Center, Dahlgren Division, Dahlgren, Virginia 22448

Abstract

Three polyureas with decreasing soft segment molecular weights of 1000, 650, and a 250/1000 blend were molded onto circular steel plates and then impacted with a high speed (275 m/s) conical-shaped steel cylinder. The polyurea layer of the post mortem bilayers was characterized on a molecular level by small angle synchrotron X-ray scattering (SAXS) at the Advanced Photon Source at the Argonne National Laboratory. Analysis revealed that the hard domains of the polyureas with lower molecular weight soft segments reformed and oriented over a greater area of the coating, thus increasing the polymer strain hardening and resulting in visibly less out of plane bilayer deformation. This agrees with the hypothesis that polymer strain hardening is a mechanism that retards necking failure of the metal plate.

(Received March 02 2011)

(Accepted March 08 2011)

Key Words:

  • polyureas;
  • soft segment molecular weight;
  • high speed impact;
  • SAXS;
  • morphology