3M™ Glass
Bubbles K15
Low density with improved processing strength
SODA-LIME BOROSILICATE • HOLLOW MICROSPHERES
Engineered hollow glass spheres that displace heavier fillers and resin with stable, non-porous voids—helping reduce weight while supporting flow, sanding, insulation and dimensional control.
Maximum volume. Minimum mass.
K15 balances very low density with higher crush resistance than K1. Its hollow, spherical geometry occupies formulation volume at a fraction of the mass of conventional mineral fillers.
Very low density
Reduces composite density and may lower weight-based filler demand.
Low heat flow
Stable internal voids provide very low calculated thermal conductivity.
Improved processing
Spherical particles can support lower viscosity, better flow and higher volume loading.
Stable filler
Water-resistant, chemically stable, non-combustible and non-porous glass.
BUILT INTO
LIGHTWEIGHT
COMPOUNDS
K15 can contribute volume without excessive weight in wall repair compounds and coatings. The visual shows easy sanding and a thermal-coating application concept.
Original conceptual application image. Final performance depends on matrix, loading, mixing and processing pressure.
K15 within the K series
Density rises as stronger K-series grades use more glass structure. Select K15 when minimum density is the priority and process pressure remains compatible with its 300 psi strength level.
Typical true density (g/cm³)
Isostatic crush test pressure (psi)
Where K15 creates value
K15 is best matched to formulations and processes that do not expose the bubbles to pressure above their survival capability.
LIGHTWEIGHT WALL
REPAIR
Volume, reduced mass, easy sanding and a flush paintable finish.
PAINTS & COATINGS
Lower dry-film density and stable voids for insulation-oriented formulations.
CAULKS & ADHESIVES
Lightweight volume extension with non-porous spherical filler geometry.
SYNTACTIC FOAM
Buoyancy in suitable shallow-water systems following pressure validation.
CAST POLYESTER & PUTTY
Reduced density, shrinkage and warpage with appropriate processing.
EMULSION EXPLOSIVES
Density modification where grade survival and process compatibility are confirmed.
Protect the hollow structure
Glass-bubble performance depends on keeping the spheres intact through mixing, transfer and application.
Use low-shear incorporation
Where practical, introduce glass bubbles after high-shear dispersion of other pigments and fillers.
Check the whole process
Evaluate mixer shear, pumping, filtration, spray pressure, casting and compaction against K15’s 300 psi level.
Correct for density
Do not replace dense mineral filler pound-for-pound. Recalculate on volume and target formulation density.
TECHNICAL PROFILE
Typical values are for grade selection and are not release specifications. Use the current 3M technical data sheet and SDS for final qualification.
| Property | K15 typical data |
|---|---|
| Composition | Water-resistant, chemically stable soda-lime borosilicate glass |
| Appearance | White, free-flowing hollow microsphere powder |
| Typical true density | 0.15 g/cm³ |
| True density range | 0.13–0.17 g/cm³ |
| Isostatic crush test pressure | 300 psi |
| Fractional survival | 90% target; 80% minimum |
| Particle size by volume | D10 30 µm; D50 60 µm; D90 105 µm; effective top size 115 µm |
| Calculated thermal conductivity | 0.055 W/m·K at 21°C |
| Typical floaters | 96% by bulk volume; 90% minimum |
| Dielectric constant, K series | 1.2–1.7 at 100 MHz, theoretical calculation only |
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