Title

Chemical, Physical, and Mechanical Characterization of Isocyanate Cross-linked Amine-modified Silica Aerogels

Abstract

We describe a new mechanically strong lightweight porous composite material obtained by encapsulating the skeletal framework of amine-modified silica aerogels with polyurea. The conformal polymer coating preserves the mesoporous structure of the underlying silica framework and the thermal conductivity remains low at 0.041 ± 0.001 W m-1 K-1. The potential of the new cross-linked silica aerogels for load-carrying applications was determined through characterization of their mechanical behavior under compression, three-point bending, and dynamic mechanical analysis (DMA). A primary glass transition temperature of 130 °C was identified through DMA. At room temperature, results indicate a hyperfoam behavior where in compression cross-linked aerogels are linearly elastic under small strains (<4%) and then exhibit yield behavior (until 40% strain), followed by densification and inelastic hardening. At room temperature the compressive Young's modulus and the Poisson's ratio were determined to be 129 ± 8 MPa and 0.18, respectively, while the strain at ultimate failure is 77% and the average specific compressive stress at ultimate failure is 3.89 × 105N m kg -1. The specific flexural strength is 2.16 × 104 N m kg-1. Effects on the compressive behavior of strain rate and low temperature were also evaluated.

Department(s)

Chemistry

Keywords and Phrases

Amine-modified Silica Aerogels; Compressive Behavior; Load-carrying Applications; Aerogels; Amines; Chemical Modification; Crosslinking; Dynamic Mechanical Analysis; Elastic Moduli; Poisson Ratio; Strain Rate; Temperature Distribution; Thermal Conductivity; Silica

International Standard Serial Number (ISSN)

0897-4756

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2006 American Chemical Society (ACS), All rights reserved.


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