York DW, Collins S, Rantape M. Measuring the permeability of thin solid layers of natural waxes.
J Colloid Interface Sci 2019;
551:270-282. [PMID:
31096136 DOI:
10.1016/j.jcis.2019.03.104]
[Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 03/28/2019] [Accepted: 03/30/2019] [Indexed: 11/29/2022]
Abstract
HYPOTHESIS
Previous experimental work has shown that microcapsule walls, made by solidification of a molten wax, are unexpectedly permeable. The hypothesis was that this was due more to the structure of the wall than the material itself.
EXPERIMENTS
The permeability of thin (sub and low micron thickness) natural waxes was measured where a membrane was placed between two cells and the diffusion of a dye (fluorescein) measured. A filter paper was used to support the membranes. Two methods were used to coat the filter paper; simple dipping and spin coating. The resulting surfaces were examined using SEM, XRD and contact angle.
FINDINGS
Results indicate that the permeability of very thin walled capsules can be investigated by forming a layer on a porous support and measuring diffusion rates. Both the composition of the wax and the sample preparation is extremely important to the structure and resulting permeability of the membranes. Spin coating was much more effective than dip coating in reducing permeability. Carnauba wax had a much lower permeability than beeswax. A difference in levels between the two cells was observed, indicating a potential Osmotic pressure difference at play which should be further investigated.
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