CHEMICAL MODIFICATION OF TANNIN/FURANIC RIGID FOAMS BY ISOCYANATES AND POLYURETHANES

X. Li, M.C. Basso, V. Fierro, A. Pizzi, A. Celzard

Abstract


Tannin/furanic rigid foams were modi ed by either polymeric 4,4’ diphenylmethane diisocyanate(pMDI) or a one-component polyurethane still presenting reactive isocyanate groups (PUR). Severaldi erent sequences of mixing the isocyanate and polyurethane with the chemicals used to preparetannin-based foams were tested. Scanning electron microscopy (SEM) showed that addition of eitherpMDI or PUR yielded a more ordered microstructure of the foam and a larger cell size. Series oftwo di erent cell sizes were noticed: those obtained by the evaporation of the blowing agent usedfor classical tannin-based foams and those caused by the formation of CO2 issued by the reactionof the isocyanate groups with water. e cell size, density, thermal conductivity and mechanicalproperty of tannin/furanic foams were controlled by changing the amount of blowing agent andweight fraction of pMDI. e cell size of pMDI modi ed foams was largest when the weight fractionof pMDI was 5% and kept decreasing as the pMDI percentage became higher. e density of thefoams increased with the increase of the weight fraction of pMDI. e addition of pMDI increasedslightly the thermal conductivity of tannin/furanic foam with the foams still presenting good thermalinsulation. Moreover, the addition of pMDI in tannin/furanic foams improved markedly the foam’smechanical properties.

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