Samuele Giovando

Alkaline Tannin Rigid Foams

Condensed fl avonoid tannin foams were obtained under alkaline conditions. This entailed the elimination of furfuryl alcohol from these formulations, as under alkaline conditions, foam preparation could not rely on the heat generated by the self-condensation of furfuryl alcohol, which occurs only under strongly acidic conditions. The approach used to formulate the alkaline foam was: (i) the total elimination of furfuryl alcohol from the formulation, (ii) coupled with the use of an aldehyde hardener different from formaldehyde (for environmental reasons) and (iii) the application of moderate heat to allow foaming. These were not tannin/ furanic foams as their acid-curing counterparts, but tannin only foams. The open cell foams were evaluated for bulk density, compressive strength, thermal conductivity and fi re resistance. Their characteristics were similar to the acid-curing tannin/furanic foams.

Phenolic resin adhesives based on chestnut (Castanea sativa) hydrolysable tannins

Chestnut hydrolysable tannins are phenolic materials that have been considered too unreactive to compete in the phenolic resin adhesives market for exterior boards for the building industry. However, an article in 1973 describing 3 years industrial application of chestnut hydrolysable tannins during the first oil crisis indicated that this was not the case. We have extended this old work by using superior phenolic resins formulations and producing phenol–formaldehyde–chestnut tannin adhesives where a substitution of up to 80% of the phenol is possible with remarkably good results. The reactions involved were clarified by 13C NMR and MALDI-TOF mass spectrometry.

Matrix-Assisted Laser Desorption-Ionization Time of Flight (MALDI-TOF) Mass Spectrometry of Phenol-Formaldehyde-Chestnut Tannin Resins

Natural hydrolysable chestnut tannin extracts used to partially substitute phenol in Phenol-Formaldehyde (PF) resins for phenolic rigid foams were analysed by matrix-assisted desorption ionization time of flight (MALDI-TOF) mass spectrometry. PF only, chestnut only and PF-chestnut copolymerised oligomer types and distribution were determined. MALDI-TOF analyses of a PF control resin (with the same molar ratio) and of chestnut tannin extracts were performed in order to identify the peaks of molecular weights corresponding to copolymers of chestnut tannins with phenol and formaldehyde.

Development and Characterisation of Phenolic Foams with Phenol-Formaldehyde-Chestnut Tannins Resin

With the depletion of fossil resources, tannin extracts can be a natural alternative to some synthetic products. Hydrolysable chestnut tannin extracts have been used to partially replace phenol in PF resins for phenolic rigid foams. Phenol-formaldehyde-chestnut tannin (PFT) phenolic foams were initially made from copolymerized PFT resins of different molar ratio. The PFT foams so prepared were tested for thermal conductivity, these being slightly worse than that of pure PF foams; and for mechanical and water absorption, these two properties being better than those of pure PF foams. Indeed, PF resins represent an important part of synthetic resins. They are used in different fields of application such as in phenolic foams or for the preparation of particleboard. So it is important to work on the possibility of going green with these resins.

Phenolic resin wood panel adhesives based on chestnut ( Castanea sativa ) hydrolysable tannins

Abstract Chestnut hydrolysable tannins are phenolic materials that have been considered too unreactive to compete in the phenolic resin adhesives market for exterior boards for the building industry. However, an article in 1973 describing 3 years of industrial application of chestnut hydrolysable tannins during the first oil crisis indicated that this was not the case. This previous work has been extended by using superior phenolic resins formulations and producing phenol–formaldehyde–chestnut tannin adhesives where a substitution of up to 80% of the phenol is possible with remarkably good results. The reactions involved were clarified by 13C NMR and MALDI–TOF mass spectrometry.