Granulation, the process of formation of granules from a combination of base
powders and binder liquids, has been a subject of research for almost 50 years,
studied extensively for its vast applications, primarily to the pharmaceutical
industry sector. The principal aim of granulation is to form granules comprised
of the active pharmaceutical ingredients (API’s), which have more desirable
handling and flowability properties than raw powders. It is also essential to
ensure an even distribution of active ingredients within a tablet with the goal of
achieving time-controlled release of drugs.
Due to the product-specific nature of the industry, however, data is largely
empirical [1]. For example, the raw powders used can vary in size by two orders
of magnitude with narrow or broad size distributions. The physical properties of
the binder liquids can also vary significantly depending on the powder
properties and required granule size.
Some significant progress has been made to better our understanding of the
overall granulation process [1] and it is widely accepted that the initial
nucleation / wetting stage, when the binder liquid first wets the powders, is key
to the whole process. As such, many experimental studies have been conducted
in attempt to elucidate the physics of this first stage [1], with two main
mechanisms being observed – classified by Ivenson [1] as the “Traditional
description” and the “Modern Approach”. See Figure 1 for a graphical definition
of these two mechanisms. Recent studies have focused on the latter approach [1] and a new, exciting
development in this field is the Liquid Marble. This interesting formation occurs
when a liquid droplet interacts with a hydrophobic (or superhydrophobic)
powder. The droplet can become encased in the powder, which essentially
provides a protective “shell” or “jacket” for the liquid inside [2]. The liquid inside
is then isolated from contact with other solids or liquids and has some
fascinating physical properties, which will be described later on. The main
potential use for these liquid marbles appears to be for the formation of novel,
hollow granules [3], which may have desirable properties in specific
pharmaceutical applications (e.g. respiratory devices). They have also been
shown to be a highly effectively means of water recovery and potentially as
micro-transporters and micro-reactors [4].
However, many studies in the literature are essentially proof-of-concept
approaches for applications and a systematic study of the dynamics of the
marble formation and the first interactions of the liquid droplet with the powder
is lacking. This is the motivation for this research project, where we aim to
provide such information from an experimental study of drop impact onto
hydrophobic powders with the use of high-speed imaging.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/277453 |
| Date | 12 1900 |
| Creators | Khalil, Kareem |
| Contributors | Thoroddsen, Sigurdur T, Physical Science and Engineering (PSE) Division, Claudel, Christian G., Marston, Jeremy |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | 2015-01-01, At the time of archiving, the student author of this thesis opted to temporarily restrict access to it. The full text of this thesis became available to the public after the expiration of the embargo on 2015-01-01. |
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