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Impact of Colloidal Silica on Silicone Oil-Silica Mixed Antifoams

Yuan, Zheng
http://orcid.org/0000-0002-2368-0315
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562587653182

Abstract Details

2017, MS, University of Cincinnati, Engineering and Applied Science: Materials Science.
Antifoams are utilized as an industrial additive to control undesired foam during processing. This study focuses on the impact of silica on the antifoam stability. Antifoam stability refers to the ability to maintain efficiency in foam destruction after prolonged shelf storage. Common antifoams are a mixture of hydrophobic silica particles and silicone oil. Based on the general mechanisms of antifoam action discussed in Chapter 1, silica particles play a significant role in foam destruction. Silica particles contribute to foam control by facilitating the entry and the penetration depth of oil-silica globules into surfactant-water films (foam bubble walls). The size, morphology and hydrophobicity of silica can be manipulated to generate optimal antifoam globules. For example, the two silicas with good shelf life performance (8375 and 9512) had the largest silica particles and both showed a tendency to aggregate in toluene solution. We conclude that improved shelf life is related to the propensity of PDMS oil to adsorb on silica, which leads to aggregation and particle size increase. We measured the time-evolution of dynamic light scattering (DLS) from 3-vol% antifoam dissolved in toluene (Chapter 2). For the sample with the largest hydrodynamic radius (9512) the scattered intensity decreased significantly after applying ultrasonic dispersion. Decreasing intensity also occurred for 8375 albeit at later times. The decrease of intensity is attributed to the growth and precipitation of oil-silica globules. The concentration dependence of light scattering confirmed the growth-precipitation hypothesis. FT-IR (Chapter 3) was consistent with precipitation due to oil adsorption, but the data were not definitive. Chapter 4 examines the time-evolution of silica structures by static light scattering and X-ray scattering. The combined data are consistent with a hierarchical structure for silica. Agglomeration occurred fastest for 9512, which is consistent with DLS observations above. The last chapter concludes that PDMS-silica adhesion controls antifoam stability. The decline in performance with shelf-life aging is attributed to loss of hydrophobicity of silica, which could be due to adsorption of surfactants or some chemical alteration of the hydrophobic silica surface.
Dale Schaefer, Ph.D. (Committee Chair)
Gregory Beaucage, Ph.D. (Committee Member)
Yoonjee Park, Ph.D. (Committee Member)
58 p.
Materials Science
colloidal silica; antifoam; light scattering; X-ray scattering

Recommended Citations

Citations

  • Yuan, Z. (2017). Impact of Colloidal Silica on Silicone Oil-Silica Mixed Antifoams [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562587653182

    APA Style (7th edition)

  • Yuan, Zheng. Impact of Colloidal Silica on Silicone Oil-Silica Mixed Antifoams. 2017. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562587653182.

    MLA Style (8th edition)

  • Yuan, Zheng. "Impact of Colloidal Silica on Silicone Oil-Silica Mixed Antifoams." Master's thesis, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562587653182

    Chicago Manual of Style (17th edition)

ucin1491562587653182
717
© 2017, some rights reserved.Creative Commons License Impact of Colloidal Silica on Silicone Oil-Silica Mixed Antifoams by Zheng Yuan is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.