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Acid‐ and alkali‐catalyzed tannin‐based rigid foams
Author(s) -
Meikleham N. E.,
Pizzi A.
Publication year - 1994
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1994.070531117
Subject(s) - tannin , formaldehyde , furfuryl alcohol , polymer , alkali metal , catalysis , materials science , blowing agent , copolymer , phase (matter) , chemical engineering , chemistry , polymer chemistry , composite material , organic chemistry , polyurethane , food science , engineering
Acid‐ and alkali‐catalyzed polyflavonoid tannin‐based rigid foams were prepared. These foams have comparable physical and mechanical properties to the synthetic phenolic rigid foam used as a comparative standard. The fluid polymer phase was based on a mimosa tannin‐formaldehyde resin with a minor addition of a fortifier resin. Expansion of the fluid phase was brought about by a physical blowing agent, whereas dimensional stabilization was achieved through cross‐linking at the desired density. In the case of the acid‐catalyzed foam, a heat‐generating agent in the form of furfuryl alcohol was employed. The polymer composition of tannin–formaldehyde/urea–formaldehyde systems as a function of pH was predicted from the respective gel times and rate constants, i.e., above pH 7, the copolymer proportion will tend to 100% and, that at pH 3.4, the polymer blend proportion will tend to a maximum. © 1994 John Wiley & Sons, Inc.