| abstract |
Method for making hollow microspheres of substantially uniform diameter and of substantially uniform wall thickness is disclosed. The walls of the hollow microspheres comprise sintered together particles which define interconnecting voids within the walls and a single central cavity in the interior of the microspheres and inner and outer microsphere wall surfaces. The interconnecting voids are continuous and extend from the outer wall surface to the inner wall surface. The walls have substantially uniform void content and the interconnecting voids are substantially uniformly distributed in the walls of the hollow microspheres and the walls of the hollow microspheres are free of latent solid or liquid blowing gas materials and are substantially free of relatively thinned wall portions and bubbles. The method includes heating the microspheres for a sufficient period of time to close and seal the interconnecting void. |