Zeta Potential and Fiberglass Mat

2011 Building & Industrial Mat Spring Meeting

F. Philip Yu, Ph.D & Blaine Krause Nalco Company 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

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

• 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. 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 Remote Microbial Accessible Activity

Real ORP Time Temperature Fouling Biodemand Changes with Different Wet Chops

Fiber B Fiber A Fiber B Fiber A