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Avoiding "mud" cracks during drying of thin films from aqueous colloidal suspensions
E Santanach Carreras1, F Chabert, D E Dunstan
1Department of Chemical & Biomolecular Engineering, The University of Melbourne, Vic 3010, Australia.
Journal of Colloid and Interface Science
|May 25, 2007
Summary
Investigating alumina films reveals that dispersed suspensions yield films with 3x greater critical cracking thickness than flocculated ones. Adding poly(vinyl alcohol) (PVA) doubles this thickness, while crosslinking PVA increases it tenfold.
Area of Science:
- Materials Science
- Ceramic Engineering
- Polymer Science
Background:
- Drying of aqueous suspensions is crucial for fabricating ceramic films.
- Film cracking during drying is a common issue affecting mechanical properties.
- Understanding factors influencing critical cracking thickness is essential for material design.
Purpose of the Study:
- To investigate the critical cracking thickness of alumina films during drying.
- To evaluate the effects of suspension chemistry, binder addition, and binder crosslinking on film integrity.
- To compare film properties derived from flocculated versus dispersed alumina suspensions.
Main Methods:
- Preparation of aqueous alumina suspensions with varying solution chemistry.
- Inclusion of poly(vinyl alcohol) (PVA) as a polymeric binder.
- Covalent crosslinking of PVA in selected dispersed suspensions.
- Drying of prepared films and measurement of critical cracking thickness.
Main Results:
- Films from dispersed suspensions exhibited a critical cracking thickness three times greater than those from flocculated suspensions.
- Addition of PVA increased the critical cracking thickness by a factor of two for both suspension types.
- Crosslinking PVA resulted in a tenfold increase in critical cracking thickness compared to uncrosslinked PVA systems.
Conclusions:
- Dispersed alumina suspensions yield films with superior mechanical properties due to higher final solids concentration.
- Polymeric binders like PVA significantly enhance film crack resistance.
- Crosslinking of binders offers a substantial improvement in film mechanical integrity during drying.
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