Foamed using a hand mixing method Foamed using spraying equipment
Rigid PUR foam composition name FP-25 FP-45 FS-3
PUR foam composition., pbw      
Polyol from renewable resources 85 86 80
Cross linking polyols (Lupranol 3422) 15 15 20
Water 2   4
c-pentane 13 13  
Catalysts 1,2 0,6 1,2
Surfactant 1,5 1,5 1,5
Polyol component 117,7 116,1 106,7
Polyisocyanate 150,5 114,3 225,4
Characteristics of the system  
Isocyanate index 125 125 145
Renewable materials in polyurethane foam, % 25,1 28,7 23,46
Technical parameters at 20 °C      
Start time, s 16 31 10
String time, s 44 60 34
End time, s 65 85 60
Tack free time, s 58 75 54
Rigid PUR foam characteristics  
Free rise density, kg/m3 29 39 33
Density when foamed in a mould, kg/m3 46 66 -
Compression strength (parallel foaming direction)  
EMod, MPa 3,98 6,77 4,66
σMax, Mpa 0,18 0,28 0,16
Other PUR foam characteristics  
Closed cell content, % 89,50 92,70 89,40
Water absorption (after 7 days), % - 1,81 1,90
Thermal conductivity test  
Apparent Density, kg/m3 46,20 66,10 -
Average Lambda value, mW/mK 21,93 22,95 -

Our polyols, which are from renewable resources, should be always used alongside cross-linking polyols with a functionality of more than five. For this we suggest using the Lupranol 3422 polyol from BASF (BASF The Chemical Company). All blowing agents currently used in the polyurethane industry are suitable for compositions with our polyols. The Institute of Wood Chemistry of Latvia (IWC) studied water and c-pentane blowing agents, obtaining stable, high quality, rigid polyurethane compositions. As catalysts, tertiary amine compounds were used, but for a catalysis trimerization reaction of isocyanate potassium, an acetate solution in diethylene glycol was used.

FP-25 and FP-45 polyurethane compositions were foamed by a hand mixing method in an open mould but the FS-3 composition was foamed using spraying equipment. An isocyanate component pMDI from BASF (Lupranat M20R) was used. Rigid polyurethane materials obtained from these compositions contain up to 29 percent of renewable materials, and in the end product, compression strength, closed cell content, density, and thermal conductivity is comparable with commercially used polyurethane foams from petrochemical materials. An interesting benefit of our polyols is that the polyurethane materials show very high hydrophobicity characteristics, which are good for thermal insulation materials.

We believe it is possible to obtain better thermal conductivity characteristics in polyurethane foams than IWC obtained from their samples. Thermal conductivity of 0.022 W/mK can be explained by the high density of prepared samples through the method of obtaining samples in moulds. Better mixing techniques could improve the cell structure of rigid polyurethane foams, which would improve thermal conductivity characteristics.