Foam formation and characterization.(Generation of Microcellular Polyurethane Foams via Polymerization in Carbon Dioxide, part 2): An article from: Polymer Engineering and Science
Book Details
Author(s)Kristen L. Parks, Eric J. Beckman
PublisherSociety of Plastics Engineers, Inc.
ISBN / ASINB00096P2IU
ISBN-13978B00096P2I7
MarketplaceCanada 🇨🇦
Description
This digital document is an article from Polymer Engineering and Science, published by Society of Plastics Engineers, Inc. on October 15, 1996. The length of the article is 8056 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.
From the author: Microcellular polyurethane foams are generated through phase separation, which is induced by reaction-induced crosslinking or by a pressure quench. The phase separation conditions are shown to impact the microstructure of the foams. Pore growth will occur through two mechanisms: diffusion of C[O.sub.2] from polymer-rich regions into the pores and also through C[O.sub.2] gas expansion (boiling of liquid C[O.sub.2] at reduced pressure). Higher C[O.sub.2] pressures for polymerization (hence, higher fluid density) provide more C[O.sub.2] molecules for foaming, generate lower interfacial tension and viscosity in the polymer matrix, and thus produce higher cell densities. Increasing the functionality of the polyurethane precursors increases the [T.sub.g] of the polymer network and leads to smaller cell diameters by raising the vitrification pressure and allowing less time for C[O.sub.2] gas expansion to play a role in cell growth. Higher reaction temperatures result in an increase in bulk density as the cell density remains invariant and the cell size drops. The use of the more polar fluoroform as a foaming agent results in larger cells, as it is able to plasticize the polymer network and allow for gas expansion during depressurization. A constant composition method of pressure quench results in smaller cell diameters.
Citation Details
Title: Foam formation and characterization.(Generation of Microcellular Polyurethane Foams via Polymerization in Carbon Dioxide, part 2)
Author: Kristen L. Parks
Publication:Polymer Engineering and Science (Refereed)
Date: October 15, 1996
Publisher: Society of Plastics Engineers, Inc.
Volume: v36 Issue: n19 Page: p2417(15)
Distributed by Thomson Gale
From the author: Microcellular polyurethane foams are generated through phase separation, which is induced by reaction-induced crosslinking or by a pressure quench. The phase separation conditions are shown to impact the microstructure of the foams. Pore growth will occur through two mechanisms: diffusion of C[O.sub.2] from polymer-rich regions into the pores and also through C[O.sub.2] gas expansion (boiling of liquid C[O.sub.2] at reduced pressure). Higher C[O.sub.2] pressures for polymerization (hence, higher fluid density) provide more C[O.sub.2] molecules for foaming, generate lower interfacial tension and viscosity in the polymer matrix, and thus produce higher cell densities. Increasing the functionality of the polyurethane precursors increases the [T.sub.g] of the polymer network and leads to smaller cell diameters by raising the vitrification pressure and allowing less time for C[O.sub.2] gas expansion to play a role in cell growth. Higher reaction temperatures result in an increase in bulk density as the cell density remains invariant and the cell size drops. The use of the more polar fluoroform as a foaming agent results in larger cells, as it is able to plasticize the polymer network and allow for gas expansion during depressurization. A constant composition method of pressure quench results in smaller cell diameters.
Citation Details
Title: Foam formation and characterization.(Generation of Microcellular Polyurethane Foams via Polymerization in Carbon Dioxide, part 2)
Author: Kristen L. Parks
Publication:Polymer Engineering and Science (Refereed)
Date: October 15, 1996
Publisher: Society of Plastics Engineers, Inc.
Volume: v36 Issue: n19 Page: p2417(15)
Distributed by Thomson Gale
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