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Superinsulating Polyisocyanate Based Aerogels: A Targeted Search for the Optimum Solvent System
Zhiyuan Zhu1, Geert M B F Snellings2, Matthias M Koebel1
1Laboratory for Building Energy Materials and Components, Swiss Federal Laboratories for Materials Science and Technology, EMPA , Überlandstrasse 129, 8600 Dübendorf, Switzerland.
ACS Applied Materials & Interfaces
|May 9, 2017
Summary
This study reveals that polyurethane-polyisocyanurate (PUR-PIR) aerogel properties, like thermal conductivity, are highly tunable by selecting specific gelation solvents based on Hansen solubility parameters. Optimal performance is achieved with high hydrogen bonding and dispersion forces in the solvent blend.
Area of Science:
- Materials Science
- Polymer Chemistry
- Nanotechnology
Background:
- Polyisocyanate aerogels offer superior mechanical properties and ultralow thermal conductivity compared to silica aerogels.
- The critical role of gelation solvent in determining aerogel properties is well-recognized but not systematically explored.
- Understanding solvent-gelation solvent interactions is key for optimizing aerogel performance.
Purpose of the Study:
- To systematically investigate the relationship between gelation solvent Hansen solubility parameters and the resulting polyurethane-polyisocyanurate (PUR-PIR) aerogel microstructure, surface area, thermal conductivity, and density.
- To identify optimal solvent compositions for producing PUR-PIR aerogels with minimized thermal conductivity.
- To elucidate the specific influence of dispersion, polarity, and hydrogen bonding parameters of the solvent on aerogel characteristics.
Main Methods:
- Preparation of PUR-PIR aerogels using a rigid foam formulation in various solvent blends.
- Systematic variation of acetone-dimethyl sulfoxide (DMSO) ratios and subsequent screening of 32 different solvent blends with fixed Hansen solubility parameters (δD, δP, δH).
- Characterization of aerogel properties including thermal conductivity (λ), specific surface area, and density.
Main Results:
- An optimal acetone:DMSO ratio of 85:15 v/v was identified, yielding minimum thermal conductivity and maximum specific surface area.
- Aerogel properties showed distinct dependencies on Hansen solubility parameters: low thermal conductivity was achieved with high δH-bonding (>7.2 MPa¹/²) and moderate δDispersion (~16.3 MPa¹/²).
- The δPolarity parameter was found to be less influential on the final aerogel properties.
Conclusions:
- The choice of gelation solvent is a critical parameter for tailoring PUR-PIR aerogel properties.
- Hansen solubility parameters provide a valuable framework for predicting and optimizing solvent selection for aerogel synthesis.
- This study offers a methodology for targeted solvent screening to achieve desired aerogel characteristics, particularly low thermal conductivity.
