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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Stimulated jet break-up for production of uniform size microgel beads from cross linked sodium alginate solutions

Gill, Hardeepak (Happy) Singh 04 October 1996 (has links)
The goal of this thesis was to develop a process of producing small monodisperse alginate gel beads. The phenomenon of controlled jet break-up of alginate solution jet with assisted vibration was used to form uniform sodium alginate droplets which were subsequently crosslinked with divalent calcium ion to form gel beads. Producing uniform alginate beads below 500 microns has been a problem which previous researchers have faced. Also, there is no commercially viable system available which can produce microbeads of uniform size. This study was an attempt to solve some of these problems. Vibration was applied to the alginate solution jet in both axial and transverse direction to cause jet break-up. Also, different modes of transmitting the vibration to the jet, like vibrating the full assembly or vibrating a diaphragm, were investigated. This resulted in construction of different types of bead generator apparatus. The droplet formation involves the formation of a jet through an orifice and superposition of vibration in order to control the break-up the jet. Both of these fluid flow phenomena depend on the properties of the liquid used to form the droplets. Specifically, the viscoelastic properties of the liquid play a major role in determining the break-up dynamics of the jet. The rheology of the Keltone LV (alginate) solutions (1-2% w/v) was studied using a rotational Bohlin CS-50 Rheometer and a Clark High Shear Capillary Viscometer. The best results were obtained by using the axial vibrating diaphragm droplet generator. Good monodispersed beads (160-1000 microns) were produced by using two different size orifices 100 micron and 200 microns. The vibration frequency range used was 200-6000 Hz and the flowrate range was 2-7 ml/min. The alginate droplets were crosslinked in 0.1 M calcium chloride and the shrinkage of the alginate droplets due to gelation was studied over a period of 7 days. Based on our study a design for producing sub-100 micron size beads has been proposed which uses a piezoceramic crystal for producing high frequency vibrations. / Graduation date: 1997

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