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Title: Understanding liquid movements in textiles for the development of liquid repellent strategies
Author: Zhang, Gannian
ISNI:       0000 0004 7966 6218
Awarding Body: Queen Mary University of London
Current Institution: Queen Mary, University of London
Date of Award: 2018
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The understanding of the liquid movements in textiles is important to the development of novel liquid repellent strategies based on the manipulation of liquid motion. In this thesis we focus on the two areas that have received little attention: (1) the liquid permeation across the thickness of a single-layer textile following the deposition of a static droplet and (2) the liquid movements following the impact of droplets on a single-layer textile. In the study of area (1) we report a time-resolved high resolution X-ray imaging of the motion of the liquid-vapour interface in the textile thickness direction. The imaging of the time-dependent position of the interface is made possible by the use of ultra-high viscosity liquids (dynamic viscosity 2.5·106 times higher than that of water). Imaging results suggested a three-stage permeation mechanism with each stage being associated with one type of capillary channels in the textile geometry. We also showed that the permeation dynamics cannot be described by the popular Washburn theory. In the study of area (2) we record the impact of droplets on textiles with high-speed imaging. We showed that the impact on textiles at short timescales involved no droplet shape deformation if the textile's porosity was sufficiently high. We also showed that droplets could be captured by the textiles under some impact conditions. By balancing the dynamic and capillary pressures we showed that the droplet penetration was governed by a threshold pore size and the droplet diameter. Moreover, we identified 5 stages for the liquid spreading on the textile surfaces following the impact. Within the investigated range of impact velocity the surface chemistry of the textiles was unimportant in the determination of liquid repellency. We also investigated the transplanar liquid permeation across non-wettable textiles following the deposition of droplets. We showed that the permeation was governed by a critical pore size and the weight of the deposited liquid. We discussed the limitation of the Gillespie scaling, developed for the prediction of in-plane spreading area in papers, in the description of the in-plane capillary spreading dynamics in textiles.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available