3M Scotchlite Glass Bubbles are hollow, single, microscopic spheres of insoluble, borosilicate glass.
An alternative to conventional fillers and additives, this filler and resin extender can be used in the mixing of marine putties and fairing compounds, as well as in fiberglass reinforced plastic layup.
These bubbles decrease the density of the filler and offer light weight, minimal shrinkage, and easy sanding.
For hand mixing and application, use K1 or K15 series bubbles — which have relatively low crush strengths of 250 and 300 psi, respectively.
For spray applications less than 500 psi use K20 series bubbles; for spray applications up to 750 psi use K25 series bubbles — which are able to withstand higher pressures, having crush strengths of those psi, respectively.
Note that Fisheries currently only lists K15 glass bubbles - suitable for manual application, not spraying.
Heavy on the technical side...
The unique spherical shape of 3M™ glass bubbles offers a number of important benefits, including: higher filler loading, lower viscosity/improved flow and reduced shrinkage and warpage. It also helps the 3M glass bubbles blend readily into compounds and makes them adaptable to a variety of production processes
including spraying, casting and molding.
The chemically stable soda-lime-borosilicate glass composition of 3M glass bubbles provides excellent water resistance to create more stable emulsions. They are also non-combustible and non-porous, so they do not absorb resin. Their low alkalinity gives 3M glass bubbles compatibility with most resins, stable viscosity
and long shelf life.
3M Glass Bubbles K Series, S Series and iM Series are specially formulated for a high strength-to-weight ratio. This allows greater survivability under many demanding processing conditions, such as the high pressures and shear loads of injection molding.
They also produce stable voids, which results in low thermal conductivity and a low dielectric constant.
3M glass bubbles are available in a variety of sizes and grades to help meet your product and processing requirements.