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Bubble nucleation in environmentally...

Su, Yong-Zhuo.

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Bubble nucleation in environmentally friendly processing of polymer foams.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Bubble nucleation in environmentally friendly processing of polymer foams./
作者:	Su, Yong-Zhuo.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 1996,
面頁冊數:	150 p.
附註:	Source: Dissertations Abstracts International, Volume: 58-10, Section: B.
Contained By:	Dissertations Abstracts International58-10B.
標題:	Chemical engineering. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9718465
ISBN:	9780591267341

Bubble nucleation in environmentally friendly processing of polymer foams.
Su, Yong-Zhuo.

Bubble nucleation in environmentally friendly processing of polymer foams. - Ann Arbor : ProQuest Dissertations & Theses, 1996 - 150 p.

Source: Dissertations Abstracts International, Volume: 58-10, Section: B.

Thesis (Ph.D.)--Texas A&M University, 1996.

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

Polymer foam processing is facing new challenges due to enforced environmental regulations. The physical foaming process should be the technology in the future, and it is important that we extend the knowledge base in this area. Specifically, bubble nucleation, the important fundamental step in the development of environmentally sound processing of polymer foams, has been investigated theoretically as well as experimentally. As a theoretical framework, a simple and self-consistent theory applicable to liquids where only van der Waals forces are important has been developed to predict surface tension dependence on the cluster size and temperature. Surface energies of small clusters are calculated from the intermolecular forces at a spherical surface. The developed theory of surface tension links molecular-level to bulk-level quantities in terms of the bulk properties. Predictions for macroscopic surface tension are in good agreement with the experimental values for n-alkanes and polyolefins. In general, the microsurface tension is found to decrease with decreasing radius, and such size effects occur below 2 nm; above this size, the predicted results closely approximate the planar values. The classical theories of nucleation have been extended to include intermolecular effects such as dissolved gas and cluster size effects by the continuum approach to intermolecular forces. The surface tension and contact angle, which are key parameters in free energy change of bubble formation in classical nucleation theory, can be predicted from a knowledge of material properties for the gas and polymer systems. The calculations indicate that dissolved gas effects on bubble formation energy are much more significant than cluster size effects and can explain much of the discrepancies between theory and experiment. An experimental technique has been established, which is believed to be unique and capable of giving quite accurate data on bubble nucleation pressure. With this technique, we can adjust the pressure or supersaturation by increasing the volume accurately. This method can be applied to screen the nucleating agent and to study the heterogeneous nucleation mechanism.

ISBN: 9780591267341Subjects--Topical Terms:

560457
Chemical engineering.
Subjects--Index Terms:

alkanes

Bubble nucleation in environmentally friendly processing of polymer foams.
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506 $a This item must not be sold to any third party vendors.
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520 $a Polymer foam processing is facing new challenges due to enforced environmental regulations. The physical foaming process should be the technology in the future, and it is important that we extend the knowledge base in this area. Specifically, bubble nucleation, the important fundamental step in the development of environmentally sound processing of polymer foams, has been investigated theoretically as well as experimentally. As a theoretical framework, a simple and self-consistent theory applicable to liquids where only van der Waals forces are important has been developed to predict surface tension dependence on the cluster size and temperature. Surface energies of small clusters are calculated from the intermolecular forces at a spherical surface. The developed theory of surface tension links molecular-level to bulk-level quantities in terms of the bulk properties. Predictions for macroscopic surface tension are in good agreement with the experimental values for n-alkanes and polyolefins. In general, the microsurface tension is found to decrease with decreasing radius, and such size effects occur below 2 nm; above this size, the predicted results closely approximate the planar values. The classical theories of nucleation have been extended to include intermolecular effects such as dissolved gas and cluster size effects by the continuum approach to intermolecular forces. The surface tension and contact angle, which are key parameters in free energy change of bubble formation in classical nucleation theory, can be predicted from a knowledge of material properties for the gas and polymer systems. The calculations indicate that dissolved gas effects on bubble formation energy are much more significant than cluster size effects and can explain much of the discrepancies between theory and experiment. An experimental technique has been established, which is believed to be unique and capable of giving quite accurate data on bubble nucleation pressure. With this technique, we can adjust the pressure or supersaturation by increasing the volume accurately. This method can be applied to screen the nucleating agent and to study the heterogeneous nucleation mechanism.
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