Crush strength is important when hollow glass microspheres need to survive high-shear forces and high pressures involved in manufacturing processes such as plastics compounding and injection molding. Typically, solid glass microspheres have better crush strength compared to hollow glass microspheres. If microspheres have to undergo an aggressive mechanical process, solid glass microspheres will most likely be required.
Historically, crush strength for hollow glass microsphere has been directly linked to density. That is, a glass sphere with a density of 0.125 g/ml is rated at 250 psi (1.8 MPa) while one with a density of 0.60 g/ml is rated at 18,000 psi (124 MPa). To some degree, there is a correlation between density and crush strength. The density and crush strength of hollow glass microspheres made from a particular material depends, in part, on two structural variables: wall thickness and particle size.
Hollow glass microspheres, for example, range in size from 11 to 18 microns and have crush strengths ranging from 8,000 to 10,000 psi (55 to 69 MPa), depending on the grade. They have been compounded successfully with a 25.4 mm/1-inch-diameter Killion two-stage single-screw extruder and injection molded on a 75-ton Newbury machine without significant sphere breakage.
This article comes from microspheres edit released