Table 3 Dissolution screening at pH 7.4 and pH 4.5. “Ions” = cumulated dissolved Si and Al based on ICPMS quantification of all eluted ions, in % of initial Si and Al; “S” = remaining solid mass, in % of initial MMVF mass; “k” = dissolution rate determined from cumulated dissolved ions, in ng/cm²/h

MMVF #17 (pre-1995)

Untreated – smooth surface

pH4.5 - very limited change of fibre surface after treatment: minimal roughening, no significant gel formation, no leaching pits.

MMVF #1

Untreated - binder covers entire fibre, including 100 nm to 1 μm sized particles.

pH4.5 - Very limited change of fibre surface after treatment: occasionally approx. 50 nm small leaching pits (pores).

pH7.4 – significant change of fibre surface, approx. 200nm to 1 μm gel/deposit/crater structures

MMVF #2

Untreated - smooth surface, occasional lumps of 100 nm to 1 μm sized particles.

MMVF #4

Untreated – smooth surface

pH4.5 – very significant change of fibre surface with pronounced gel; frequent occurence of approx. 400nm sized deep craters with sub-100-nm cracks at bottom.

pH4.5 – without binder, change of fibre surface with limited gel, no cracks, no pits, but approx. 200nm sized shallow structures. Thermal removal more effectiove than plasma removal of binder.

pH7.4 - very significant change of fibre surface with pronounced, inhomogenously structured gel and/or deposits, up to approx. 400nm large crater

MMVF #5

Untreated – smooth surface, occasional lumps of 100 nm to 1 μm sized particles.

pH4.5 - significant change of fibre surface with extensive gel formation, leaching with sub-100-nm sized pits and cracks. pH4.5 on respirable-only fraction also induces gel formation, leaching with sub-100-nm sized pits

pH7.4 - significant change of fibre surface, inhomogeneous leaching through gel with 1-μm-diameter honeycomb structures.

MMVF #7

Untreated – smooth surface, occasional 200 nm sized particles

pH4.5 – significant change of fibre surface with extensive gel formation, up to 4 μm sized leaching pits, occasional micro-cracks and approx. 100 nm large pores.

pH4.5 – binder removed thermally: no significant gel formation, occasional micro-cracks (intermediate gel formation if binder removed by plasma)

pH7.4 – very significant change of fibre surface with gel formation and/or deposits of up to approx. 2 μm large crystalline particles

MMVF #8

Untreated – smooth surface. Binder covers entire fibre (see ruptured crossings).

pH4.5 –significant change of fibre surface with gel formation, numerous up to approx. 100 nm sized leaching pits (pores).

MMVF #11

Untreated – smooth surface, occasional lumps of 200 nm to 1 μm sized particles

pH4.5 – very significant change of fibre surface with gel formation and deep micro-cracks (3μm x 300nm). Pitting (approx. 1 μm large spots) and approximately 200nm visible pores

MMVF #12

Untreated – rough surface, lateral cracks

pH4.5 – significant change of the fibre surface, increased smoothness. No significant gel formation, no leaching pits; pH 4.5 on respirable-only fraction: limited gel formation, no significant leaching pits.

pH7.4 – significant change the fibre surface with pronounced gel formation, inhomogenous leaching, approx. 4μm x 0.5μm sized leaching pits

MMVF #14

Untreated – binder covers entire surface, frequent inclusion of approx. 100 nm sized particles

pH4.5- significant change of fibre surface with gel formation, inhomogenous leaching, up to approx. 500 nm large leaching pits, occasionally up to approx 200 nm wide pits/pores.

pH7.4 – very significant change of fibre surface with fine grained deposits of approx. 100 to 500 nm sizes.

MMVF #20

Untreated – smooth surface, binder covers entire surface

pH4.5 – significant change of fibre surface with gel formation and erosion by frequent approx. 50 nm sized leaching pits/pores

MMVF #21

Untreated – smooth surface, very rare inclusion of approx. 200 nm sized particles

MMVF #22

Untreated – smooth surface with inclusion of approx 250 nm sized particles.

pH4.5 – significant change of fibre surface with gel formation; up to 1.5 μm diameter plateaus that have an up to 1 μm long micro crack in their center.

pH7.4 – significant change of fibre surface with gel formation, approx. 500nm diameter leaching crater

MMVF #24

Untreated – smooth surface with occasional inclusion of approx 500 nm particles

pH4.5- very significant change of fibre surface with 2 μm diameter plateaus with several approx 50 nm leaching pits on the plateaus

MMVF #26

Untreated – structured surface with approx. 200 nm to 1μm diameter elevations.

pH4.5 – significant change of fibre surface with gel formation, no leaching pits.