Processing and Mechanical Characterization of Polyurea Aerogels
MISSOURI UNIV OF SCIENCE AND TECHNOLOGY ROLLA
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The use of aerogels historically has been limited to extreme cases largely in part to the nature of their mechanical properties. Until recently many aerogels produced have been brittle and weak, though looking at their specific strength would suggest otherwise. This thesis outlines the processing and major mechanical properties of a relatively new type of aerogel, polyurea aerogel, that shows promise in a variety of fields including structures. Processing polyurea aerogel begins with a liquid solution that solidifies to form a solid gel filled with liquid that is later removed by supercritical drying. Once dry polyurea aerogels are difficult to form by standard methods such as machining without damaging the surface of the material. Because of this, methods of mold-making have been investigated to form the gel into an appropriate size and shape before the solid structure forms. It has been found that polypropylene plastic can resist the chemicals used during the manufacturing process while still being inexpensive and easy to work with. Testing has been conducted in tension, compression, bending, shear, and toughness for densities of polyurea aerogels ranging from 0.12 gcm3 to 0.31 gcm3. In most cases the strength is found to be similar to other building materials of the same density, such as balsa wood, except in the axial compression direction. After undergoing strain hardening up to approximately 40-50, polyurea aerogel strength increases exponentially and a specific failure point is difficult to determine.
- Physical Chemistry