Predicting the in vitro dissolution rate constant of mineral wool fibers from fiber composition

Abstract

Objective

We developed predictive formulae for the in vitro dissolution rate constant k_dis of acid-soluble synthetic vitreous fibers (SVF), paralleling our earlier work with glass wools, which are typically more soluble at neutral pH. Developing simple models for predicting the k_dis of a fiber can allow prediction of in vivo behavior, aid fiber developers, and potentially reduce in vivo testing.

Methods

The k_dis of several acid-soluble SVF were determined using high simulant fluid flow/fiber surface area (F/A) conditions via a single-fiber measurement system. Four fluids were employed, varying in base composition and citrate levels. Equations predicting the k_dis were derived from fiber chemistry and dissolution measurements for two of the fluids.

Results

Testing of several fibers showed a ∼10× increase in the k_dis when citrate was included in the simulant solution. Data from tests with Stefaniak’s citrate-free Phagoloysosmal Simulant Fluid (PSF) yielded k_dis values aligned with expectations from in vivo results, unlike results from citrate-containing modified Gamble’s solution. Predictive equations relating fiber chemistry to k_dis showed reasonable agreement between the measured and predicted values.

Conclusions

Citrate inclusion in the solution under high F/A conditions significantly increased the measured k_dis. This resulted in more biorelevant data being obtained using the PSF fluid with the high F/A method used. The developed predictive equations, sufficient for fiber development work, require refinement before a recommending their use in place of in vivo biopersistence testing. Significant fit improvements are possible through additional measurements under these experimental conditions.

Keywords:

• Glass wool
• mineral wool
• Gamble’s solution
• dissolution
• simulant fluid
• synthetic vitreous fiber (SVF)

Acknowledgments

We thank Andy Broderick and Heather Kessler of Owens Corning, who performed the measurements reported herein, as well as adding insights that aided in cell design. We also acknowledge Adam Davis of Owens Corning for his assistance with the detailed design and 3D printing of our updated single-fiber test cells.

Author contributions

RMP: Study design, experiment design, data analysis, manuscript preparation and editing; JWH: Study design, experiment design, manuscript preparation and editing; JGH: Study design, manuscript preparation and editing.

Disclosure statement

All authors are current or former employees of Owens Corning, a company engaged in the manufacture of synthetic vitreous fibers.

Data availability statement

All data generated or analyzed during this study are included in this published article [and its Supplementary Information Files].

Notes

1 In this report, we will take ‘mineral fibers’ or ‘mineral wool’ to refer to synthetic vitreous fibers (SVF) typically based on slag and stone melt formulas, as typical of those used for thermal insulation.

Additional information

Funding

This work was funded exclusively by Owens Corning.