Synthesis and Characterization of High-Performing Sulfur-Free Tannin Foams.

Jonas Eckardt,Nicola Cefarin,Gianluca Tondi,Lisa Vaccari,Alexander Petutschnigg,Michela Zanetti,Matthias Wind,Jonas Neubauer,Marcel Lippert,Thomas Sepperer,Sandro Donato,Thomas Schnabel

doi:10.3390/polym12030564

Abstract

Tannin foams are green lightweight materials that have attracted industrial interest for the manufacturing of sandwich panels for insulation purposes. However, the dimensions of the cells and the presence of sulfur in the formulation developed until now have discouraged their upscaling. In this work, we present the synthesis and the characterization of the more promising small cell and sulfur-free materials. It was observed that, with respect to standard ones, foams catalyzed with nitric acid present similar physical properties and more phenolic character, which favors the absorption of ionic pollutants. Conversely, the foams blown with aliphatic solvents and surfactants present smaller pores, and higher mechanical and insulating properties, without affecting the chemical properties or the heating value. The combined foam produced with nitric acid as a catalyst and petroleum ether as a blowing agent result in sulfur-free and small cell material with overall improved features. These foams have been produced at 30 × 30 × 3 cm3, with high homogeneity and, to date, they represent the most suitable formulation for industrial upscaling.

Highlights

The most commonly applied foams for the insulation of buildings in the European market are made of polystyrene or polyurethane [1,2,3]
The formulation was poured into a preheated Medium Density
We have presented foams are available, and some of them have gained industrial interest

Summary

Introduction

The most commonly applied foams for the insulation of buildings in the European market are made of polystyrene or polyurethane [1,2,3]. The tannin foams have been constantly monitored for a decade for their structure and morphology [6,7,8], and their chemical and physical properties [9,10,11]. Despite the upscaling projects performed [22], there are still some technological drawbacks to be considered: (i) the consistent presence of sulfur in the formulation due to a sulfur-based catalyst (traces of sulfites due to the extraction process could still be present), and (ii) the morphological inhomogeneity occurring during the upscaling process, which affects the properties of the foams. For filling the remaining gap between the material properties and the industrial requirements, in the present work we aim the overcome these drawbacks by using alternative formulations

Methods

Results

Conclusion