Chemical modification of tannin/furanic rigid foams by isocyanates and polyurethanes

• Autores: X. Li, M.C. Basso, V. Fierro, Antonio Pizzi, A. Celzard
• Localización: Maderas: Ciencia y tecnología, ISSN 0717-3644, ISSN-e 0718-221X, Vol. 14, Nº. 3, 2012, págs. 257-265
• Idioma: inglés
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• Resumen

  • 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). Several di erent sequences of mixing the isocyanate and polyurethane with the chemicals used to prepare tannin-based foams were tested. Scanning electron microscopy (SEM) showed that addition of either pMDI or PUR yielded a more ordered microstructure of the foam and a larger cell size. Series of two di erent cell sizes were noticed: those obtained by the evaporation of the blowing agent used for classical tannin-based foams and those caused by the formation of CO2 issued by the reaction of the isocyanate groups with water.  e cell size, density, thermal conductivity and mechanical property of tannin/furanic foams were controlled by changing the amount of blowing agent and weight fraction of pMDI.  e cell size of pMDI modi ed foams was largest when the weight fraction of pMDI was 5% and kept decreasing as the pMDI percentage became higher.  e density of the foams increased with the increase of the weight fraction of pMDI.  e addition of pMDI increased slightly the thermal conductivity of tannin/furanic foam with the foams still presenting good thermal insulation. Moreover, the addition of pMDI in tannin/furanic foams improved markedly the foam�s mechanical properties