Sprayable Aerogel Bead Compositions With High Shear Flow Resistance and High Thermal Insulation Value
- Monday, 01 April 2013
This aerogel insulation could be used in fuel cell systems, oil and gas pipelines, and in building and construction applications.
A sprayable aerogel insulation has been developed that has good mechanical integrity and lower thermal conductivity than incumbent polyurethane spray-on foam insulation, at similar or lower areal densities, to prevent insulation cracking and debonding in an effort to eliminate the generation of inflight debris.This new, lightweight aerogel under bead form can be used as insulation in various thermal management systems that require low mass and volume, such as cryogenic storage tanks, pipelines, space platforms, and launch vehicles. These aerogel beads, with a packing density of 0.03 to 0.05 g/cm3, can be used as pour-in, formable, or sprayable insulation, showing versatility in a variety of applications.
Silica and organically modified silica aerogel beads in a mixture with binders or foams can be formed into complex shapes, or sprayed onto panels. The aerogel composites have a fast cure, and have good mechanical strength at densities of 0.05 to 0.15 g/cm3. Compression modulus for the aerogel bead/foam composite was 60 percent higher than the one from the foam without aerogel dopant.
Lightweight aerogel beads can be used in sprayable form together with a carrier for on-site applications. The sprayable thermal insulator has several advantages, such as a large temperature range of operation (from cryogenic temperatures to +300 °C), facile on-site installation, can be cured at room temperature, is mechanically robust and durable, and has excellent thermal performance insulation capability. This innovation is also water repellent, but does not trap gases or cryogenic liquids and, consequently, does not pose cryopumping and cryoingestion problems.
This thermal management system can be applied in either an automated or manual spraying process with less sensitivity to process chemistry and environmental parameters than spray-on foam insulation (SOFI) products like a commercially produced polyurethane foam used on the Space Shuttle External Tank, while providing better insulation performance. The aerogel bead bindersprayed panel, with a thermal conductivity of 20 to 25 mW/mK, outperformed the commercial foam by 30 to 40 percent in the 10 to 100 °C temperature range.
The aerogel compositions developed for this innovation withstand repeated cycles of high enthalpy shear flows of 20 to 100 Pa at temperatures tested up to 370 °C without losing mechanical integrity. Thermal management systems with versatile installation based on aerogel beads represent a significant opportunity for improving performance of systems for long-term cryogenic propellant storage or transfer for mechanisms operating in cryogenic temperature environments, space transportation, and propulsion systems.