10

nanotimes Companies

10-10/11 :: October/November 2010

New Thermal Solution // German Bayer MaterialScience Developed Polyurethane Nanofoams for Thermal Insulation

B

ayer MaterialScience is working on the develop- ment of polyurethane nanofoams that could

lead to a quantum leap in thermal insulation perfor- mance several years down the road.

The Company is focusing its efforts on microemul- sions, which react under supercritical conditions (Principle of Supercritical Microemulsion Expansion, POSME) to form polyurethane rigid foams. The aim is to produce rigid foams with pore sizes of less than 150nm in diameter.

“Nanofoams of this kind achieve twice the thermal insulation performance of today‘s polyurethane foams, meaning that they could, for example, signi- ficantly reduce the energy consumption of refrige- ration appliances and, in turn, make a major contri- bution to reducing CO2

optimizing the characteristics of the microemulsions. The thermal insulation performance of a polyuretha- ne rigid foam depends chiefly on the size of the foam pores. The smaller the diameter, the lower the ther- mal conductivity and the better the insulating effect. Today‘s polyurethane rigid foams typically have pore sizes of roughly 150µm, which exceeds the pore size of nanofoams planned for the future by a factor of approximately 1,000.

To synthesize a nanofoam using the POSME method, carbon dioxide (CO2

) and the liquid polyurethane

raw materials (polyol and isocyanate) are mixed with the help of special surfactants at a pressure of 200 bar to form a microemulsion consisting of nanome- ter-sized droplets filled with CO2

and encapsulated emissions. Furthermore, the

walls of these appliances could be of thinner design, resulting in more storage space for refrigerated goods,” explained Dr. Stefan Lindner, a polyurethane rigid foam specialist at Bayer MaterialScience.

The company is partnering on this research project with Prof. Reinhard Strey from the University of Cologne‘s Institute of Physical Chemistry, who has applied for a patent on the POSME process. As part of the collaboration, his working group is engaged in

in surfactants. The pressure is then reduced, causing the CO2

bles still in the nanometer range. At the same time, the polyurethane raw materials react to form a 3D polymer network that is a rigid polyurethane foam.

“One of the trickiest challenges we face is to opti- mally coordinate the reaction of the polyurethane raw materials with the expansion of the CO2

to expand and the droplets to become bub-

bubbles

by carefully fine-tuning the processing parameters so that nanopores of the targeted diameter result,” explained Mr. Lindner. “It‘s no easy task,” added Dr.