Fabrication of Low-Density Foam Shells from Resorcinol-Formaldehyde Aerogel

Abstract

Resorcinol-formaldehyde (RF) aerogel chemistry has been used with encapsulation techniques to fabricate low-density, transparent, foam shells. To accomplish this, the gelation time was reduced from several hours to several minutes by the addition of acid following base-catalyzed RF particle growth. However, additional "annealing" of the gel for at least 20 h was needed to maximize crosslinking and minimize swelling in exchange solvents. Increasing the molar ratio of formaldehyde to resorcinol from 2 to 3 also helped to increase crosslinking. Densification of the foam shells due to dehydration during curing was greatly reduced by judicious choice of immiscible oil phases and by saturating the exterior oil phase during the annealing stage. Shells have been produced with diameters of about 2 mm, wall thicknesses ranging from 100 to 200 μm and foam densities approaching 50 mg/cc.

Department(s)

Physics

Keywords and Phrases

Annealing; Crosslinking; Curing; Dehydration; Densification; Density (specific gravity); Encapsulation; Formaldehyde; Gelation; Gels; Solvents; Swelling, Aerogels; Resorcinol, Foamed plastics

International Standard Serial Number (ISSN)

0021-8995

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Publication Date

01 Jan 1997

Link to Full Text

Share

 
COinS