Polyurethane foams with starch

Abstract

BACKGROUND: In order to meet environmentally friendly (green) chemistry requirements, substrates are increasingly in demand to enable the production of biodegradable polyurethanes. Starch seems to meet the expectations for green polyol components for application in polyurethane foam synthesis, provided that it is previously converted into liquid resin with free hydroxyl groups as a result of hydroxyalkylation. RESULTS: The synthesis of oligoetherols based on starch, functionalized with formaldehyde, glycidol and alkylene carbonates was elaborated. All reactions were performed in water as a solvent. The oligoetherols obtained were characterized by IR, 1H-NMR and MALDI-ToF spectroscopies. In the next step, the oligoetherols were applied as components for rigid polyurethane foam synthesis. The resulting foams were then tested for the following parameters: the apparent density, water uptake, dimensional stability at the temperature of 100 and 150 °C, thermal conductivity and compressive strength. The thermal resistance of foams was determined both by static and dynamic methods. The parameters of the polyurethane foams such as apparent density, water uptake and polymerization shrinkage are comparable to common rigid polyurethane foams. Several of the polyurethane foams, however, showed significantly higher thermal resistance in comparison with those obtained from standard components. CONCLUSIONS: Hydroxyalkylation of starch with formaldehyde, glycidol and alkylene carbonates in water as a solvent results in formation of oligoetherols, which can be applied for the synthesis of polyurethane foams. Several of the polyurethane foams obtained are resistant to long-term heating even at 200 °C. Additionally, after thermal exposure, their compressive strength is significantly improved. © 2018 Society of Chemical Industry.