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Solidification phenomena during drying of sol-to-gel coatings.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Solidification phenomena during drying of sol-to-gel coatings./
作者:	Cairncross, Richard Allan.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 1994,
面頁冊數:	314 p.
附註:	Source: Dissertations Abstracts International, Volume: 56-10, Section: B.
Contained By:	Dissertations Abstracts International56-10B.
標題:	Chemical engineering. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9512682
ISBN:	9798208200872

Solidification phenomena during drying of sol-to-gel coatings.
Cairncross, Richard Allan.

Solidification phenomena during drying of sol-to-gel coatings. - Ann Arbor : ProQuest Dissertations & Theses, 1994 - 314 p.

Source: Dissertations Abstracts International, Volume: 56-10, Section: B.

Thesis (Ph.D.)--University of Minnesota, 1994.

This item must not be sold to any third party vendors.

A theory of drying and reaction in liquid coatings was developed which improves upon those of Yapel (1988), Okazaki et al. (1974) and others. Equations of mass transfer by diffusion relative to a volume-averaged velocity and of heat transfer by conduction and radiation describe changes in composition and temperature within the shrinking coating. The boundary conditions of mass and energy conservation relate mass and energy flux in the coating to mass and energy flux in the drying gas. This system of equations is solved by Galerkin's method with finite element basis functions. Drying of a polymer-solvent coating without reaction is affected by the variation of diffusivity, solvent vapor pressure, and solvent activity with temperature and composition. Industrial equipment for drying polymeric coatings normally consists of a series of zones, each with a controlled temperature and airflow. This theory aided in developing a set of concepts of dryer design: use high airflow in early zones but low airflow later when drying is diffusion controlled, use as high of an oven temperature as possible without bubble formation, and use radiation heating to counteract evaporative cooling and add flexibility to dryer design. The competition between drying and reactions in liquid coatings containing precursors to random network polymers can give rise to a variety of drying phenomena. Sol-to-gel coatings containing acid catalyst, tetramethoxysilane (TMOS), methanol, and water were a model system for the theory. Skinning, or solidification of the surface of the coating while deeper material is still liquid, occurs in thick coatings when the diffusional resistance to drying is significant, i.e. at high airflow. Homogeneous solidification occurs in thin coatings or at low mass transfer coefficients. These solidification phenomena are mapped as regions in parameter space in a drying regime map. Theoretical predictions matched well with measurements of weight loss versus time and time-to-solidification, The non-equilibrium thermodynamic theory of transport in viscoelastic materials from Durning and Tabor (1986) was used to predict drying in polymer coatings. The predictions show that viscoelastic diffusion with a short relaxation time can be more rapid than Fickian diffusion.

ISBN: 9798208200872Subjects--Topical Terms:

560457
Chemical engineering.

Solidification phenomena during drying of sol-to-gel coatings.
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500 $a Source: Dissertations Abstracts International, Volume: 56-10, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
500 $a Advisor: Francis, L. F.;Scriven, L. E.
502 $a Thesis (Ph.D.)--University of Minnesota, 1994.
506 $a This item must not be sold to any third party vendors.
506 $a This item must not be added to any third party search indexes.
520 $a A theory of drying and reaction in liquid coatings was developed which improves upon those of Yapel (1988), Okazaki et al. (1974) and others. Equations of mass transfer by diffusion relative to a volume-averaged velocity and of heat transfer by conduction and radiation describe changes in composition and temperature within the shrinking coating. The boundary conditions of mass and energy conservation relate mass and energy flux in the coating to mass and energy flux in the drying gas. This system of equations is solved by Galerkin's method with finite element basis functions. Drying of a polymer-solvent coating without reaction is affected by the variation of diffusivity, solvent vapor pressure, and solvent activity with temperature and composition. Industrial equipment for drying polymeric coatings normally consists of a series of zones, each with a controlled temperature and airflow. This theory aided in developing a set of concepts of dryer design: use high airflow in early zones but low airflow later when drying is diffusion controlled, use as high of an oven temperature as possible without bubble formation, and use radiation heating to counteract evaporative cooling and add flexibility to dryer design. The competition between drying and reactions in liquid coatings containing precursors to random network polymers can give rise to a variety of drying phenomena. Sol-to-gel coatings containing acid catalyst, tetramethoxysilane (TMOS), methanol, and water were a model system for the theory. Skinning, or solidification of the surface of the coating while deeper material is still liquid, occurs in thick coatings when the diffusional resistance to drying is significant, i.e. at high airflow. Homogeneous solidification occurs in thin coatings or at low mass transfer coefficients. These solidification phenomena are mapped as regions in parameter space in a drying regime map. Theoretical predictions matched well with measurements of weight loss versus time and time-to-solidification, The non-equilibrium thermodynamic theory of transport in viscoelastic materials from Durning and Tabor (1986) was used to predict drying in polymer coatings. The predictions show that viscoelastic diffusion with a short relaxation time can be more rapid than Fickian diffusion.
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