Effect of Catalysts and Curing Temperature on the Properties of Biosourced Phenolic Foams

Biosourced phenolic foams (BPFs) based on lignin alkaline liquor and tannins were successfully synthesized without using formaldehyde and any blowing agent. The influence of three sorts of catalysis (acid, alkaline, and thermal) and different curing temperatures (80, 100, and 120 degrees C) on the final properties of the foams was investigated. Concerning foam morphology, scanning electron microscopy observations showed that a low-curing temperature could significantly reduce the cell size and improve the structural homogeneity of phenolic foams. It was also proved by Fourier transform infrared spectroscopy analysis that alkaline catalysis promotes aromatic functions, whereas the polycondensation reaction and ether linkages were dominant under acid catalysis. Thermogravimetric analysis, cone calorimetry, and Bunsen burner test revealed that the foams prepared under alkaline catalysis displayed the best thermal stability and fire resistance. The obtained BPFs exhibited a high compressive strength (0.11-1.65 MPa) and good thermal conductivity (41.5-50.55 mW/m.K which are linearly proportional to the foam densities. Accordingly, they could be used as a thermal insulator for the construction or retrofitting of buildings.

Automated summary

Biosourced phenolic foams based on lignin alkaline liquor and tannins were successfully synthesized without using formaldehyde and blowing agent. The foams prepared at lower curing temperatures showed improved structural homogeneity, while those under alkaline catalysis exhibited the best thermal stability and fire resistance.