Zeta Potential and Fiberglass Mat

F. Philip Yu, Ph.D & Blaine Krause

Nalco Company

2011

Building &

Industrial Mat

Spring Meeting

Zeta Potential

• ζ-potential (Smouluchowski’s formula)

– Indication of potential stability within a colloidal system

What is Zeta Potential?

• Zeta potential is a physical property which is exhibited by any particle in suspension

Zeta Potential & Stability

0 to ±5 mV Rapid coagulation or flocculation

±10 to ±30 mV Incipient instability

±30 to ±40 mV Moderate stability

±40 to ±60 mV Good stability

> ±60 mV Excellent stability

Dispersed Aggregated

Zeta Potential & Fiberglass Mat

• Most particles (e.g., fiberglass) dispersed in an aqueous solution will acquire a surface charge

– Ionization of surface groups

– Adsorption of charges species

• The surface charges modify the distribution of the surrounding ions, resulting in a layer surrounding the particles that is different than the bulk solution (electric double layer)

Diagram of Zeta Potential

• When a particle moves, ions in the boundary move with it. Ions beyond the boundary stay with the bulk solution.

• The Zeta Potential is the measurement of hydrodynamic shear at this boundary

• Particles with same charge (either + or -) repel each other.

The zeta potential is the potential at the point where it moves past the bulk solution

– Slipping plane

Factors Affecting Zeta Potential

• pH

– Acidic environment builds up positive charge

– Alkaline solution provides negative charge

– At isoelectric point (IEP), the zeta potential is zero.

Fiberglass ζ Potential as a function of pH

• Non-specific adsorption of sizing chemicals reduces the magnitude of zeta potential

• IEP stays the same

Fiberglass ζ Potential as a function of pH

• Specific adsorption of chemicals can change the magnitude and sign of zeta potential

• It also effectively changes the IEP (to a higher pH)

Factors Affecting Zeta Potential (cont’d)

• Conductivity

– The higher the ionic charge (conductivity), the thinner the double layer

– Specific ion adsorption could affect zeta potential and sometimes leads to charge reversal

• White water chemistry

Zeta Potential Analyzers

What does Nalco use to Measure Zeta Potential

• Mütek Particle Analyzer

– Cationic titrant (pDADMAC)

– Anionic titrant (PES-Na)

• Benchtop or portable unit

• Electrokinetic property

Electrokinetic Properties of Fiberglass Surfaces

• Four different Fiberglass samples with various charges

• Three are cationic and one anionic.

• Tap water (Chicago) carries a weak anionic charge

Electrokinetic Property of the White Water

• Once anionic viscosity modifier is added to the white water, the overwriting charge becomes anionic.

How does this impact white water chemistry performance?

• When changing glass sizing, it causes shifts in zeta potential.

• If we create an environment of consistently high charge, it keeps the glass dispersed.

• Modifying system pH can adjust the charge, it then change the dispersion

• Modifying system conductivity can impact ion adsorption, which modifies the dispersion

• Changing white water chemistry (e.g., from anionic to cationic) can drastically affect glass dispersion and cause clumping

Impact from Binder Chemistry

• Both binder and the white water ought to have similar charge to avoid poor binder performance or mat quality

• If white water is used to mix or dilute the binder, the charges should be thoroughly considered

Question?

To follow up our previous discussion on Bio-Manage for Fiberglass Mat process (2009)

OxiPRO® Monitoring

Real Time

Microbial Activity

Real Time

Fouling

ORP Temperature

Remote Accessible

Biodemand Changes with Different Wet Chops

Fiber B

Fiber B Fiber A Fiber A