Strategies to analyse data obtained from liquid intrusion experiments of loose porous materials

Geoffrey Tan, David A.V. Mortona, Ian Larson

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Liquid intrusion remains one of the most common methods to measure the contact angle of liquids to powders. However, as there are two unknown variables in the Washburn equation: the material constant (that is, the pore structure of the powder bed) and the contact angle of the liquid to the powder, this method requires the use of two liquids—a liquid of interest (the probe liquid) and a reference liquid. The reference liquid should, ideally, make a contact angle of 0° to the sample. However, in practice a low surface tension liquid is normally selected. This paper proposes a more standardised approach for the selection of the reference liquid based on experimental data. Additionally, a major assumption of the liquid intrusion method is that the pore structure, as measured by the material constant, C, is identical for all powder beds (provided that the same packing procedure is used for the same samples). In real systems, however, this is an approximation, and not likely to hold strictly true. Therefore, difficulties may arise with data analysis as there is a potential uncertainty in the most appropriate order to divide the gradient of the probe liquid by the gradient of the reference liquid. This paper proposes three specific methods of analysing such data, each with their own advantages and limitations. Hence, the selection of which method should be used is criteria-based, assessed on the basis of the obtained data.

Original languageEnglish
Pages (from-to)711-717
Number of pages7
JournalJournal of Pharmaceutical and Biomedical Analysis
Volume145
DOIs
Publication statusPublished - 25 Oct 2017

Keywords

  • Contact angle
  • Liquid intrusion
  • Material constant
  • Powder
  • Reference liquid
  • Washburn equation

Cite this

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abstract = "Liquid intrusion remains one of the most common methods to measure the contact angle of liquids to powders. However, as there are two unknown variables in the Washburn equation: the material constant (that is, the pore structure of the powder bed) and the contact angle of the liquid to the powder, this method requires the use of two liquids—a liquid of interest (the probe liquid) and a reference liquid. The reference liquid should, ideally, make a contact angle of 0° to the sample. However, in practice a low surface tension liquid is normally selected. This paper proposes a more standardised approach for the selection of the reference liquid based on experimental data. Additionally, a major assumption of the liquid intrusion method is that the pore structure, as measured by the material constant, C, is identical for all powder beds (provided that the same packing procedure is used for the same samples). In real systems, however, this is an approximation, and not likely to hold strictly true. Therefore, difficulties may arise with data analysis as there is a potential uncertainty in the most appropriate order to divide the gradient of the probe liquid by the gradient of the reference liquid. This paper proposes three specific methods of analysing such data, each with their own advantages and limitations. Hence, the selection of which method should be used is criteria-based, assessed on the basis of the obtained data.",
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Strategies to analyse data obtained from liquid intrusion experiments of loose porous materials. / Tan, Geoffrey; Mortona, David A.V.; Larson, Ian.

In: Journal of Pharmaceutical and Biomedical Analysis, Vol. 145, 25.10.2017, p. 711-717.

Research output: Contribution to journalArticleResearchpeer-review

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