Polyurethane foam is another commonly used thermal insulation foam like EPS, XPS foam.
Its thermal conductivity is 0.03W/(m*k) which is almost the same with EPS foam. The advantage of PU foams is its wide range of characteristics which offers flexibility for application.
There are mainly three kinds of polyrethane foams devided by their characteristic and application:
1. Flexible foam used in bedding, furnature and automotive seating. Low density, open-cell-structure.
2. Rigid foam used for thermal insulation panels. Low density, closed-cell-structure.
3. Spray foam insulation for building insulation. Mixture of isocyanate and polyol resin forms expanding foam and are sprayed onto roofs, concrete slabs and into wall cavities.
One interesting thing is PU foams made using aromatic isocyanates discolor exposed to visible light. It turns from off-white to yellow to reddish brown. But visible light has little effect on foam properties.
One disadvantage of PU foam is its health risk like skin and respiratory harm present in spray polyurethane foams. But fully reacted polyurethane polymer is chemically inert.
Compared to EPS foam which is preffered in my thesis, rigid PU foam offers the almost the same thermal conductivity, but with a high bending strength and stiffness. So PU foam sheet can be considered to be put on top of the panel core to improve thermal inulation.
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