Evaluation of the glycerolysis process and valorisation of recovered polyol in polyurethane synthesis

Abstract

In this study, the glycerolysis of polyurethane (PU) foam and the applicability of obtained glycerolysate (GLY) for cast PUs were investigated. It was found that crude glycerine with purity grade of 84% might be successfully used for the glycerolysis. The optimal conditions were determined as follows: reaction time of 60 min at 220 °C using dibutyltin dilaurate catalyst (0.5%). Moreover, the purification of GLY by means of liquid-liquid extraction and distillation was also adapted.Cast PUs based on GLY were prepared using a two-step method, during which a prepolymer was first synthesised from a mixture of virgin polyol, GLY and 4, 4′-diphenylmethane diisocyanate (MDI). The prepolymer was then extended with a chain extender, 1, 4-butanediol or 1, 3-propanediol. The effect of virgin polyol replacement by GLY (up to 75%) on thermal and mechanical properties of the cast PUs was determined. The PUs based on GLY exhibited slightly lower thermal stability, higher storage modulus and higher glass transition temperature than the neat PU. The tensile strength of all prepared PUs was beneficially high (12–15 MPa), while the elongation at break decreased with the increasing GLY content probable due to the branching of PU chains.