Impact of natural oil-based recycled polyols on properties of cast polyurethanes

Abstract

In this study, castor oil, rapeseed oil and medium chain triglycerides of coconut oil, were transesterified by means of 2-ethyl-2-hydroxymethyl-1,3-propanediol (trimethylolpropane) and consequently used to convert polycarbonate waste from end-of-life vehicles into liquid polyols. The prepared recycled polyols, composed uniquely of renewable and recycled components, had a hydroxyl number of ca. 250 mg KOH·g−1. They were successfully applied as 100% replacement of a virgin polyol for preparation of solid crosslinked polyurethanes (PU) by solvent-free casting. The produced rigid cast PU exhibited the main transition temperature ranging from 44°C to 53°C, the hardness value from 46 to 61 Shore D and the beneficial low water absorption (0.4-0.5 wt.%). The PU network structure was highly influenced by the presence of aromatic structures of polycarbonate-units and fatty acid compositions. A suitable selection of natural oil thus enabled to adjust thermo-mechanical properties and promote excellent optical transparency of the produced PU.