Green polyurethane foams: Replacing petrochemical polyol with castor oil through factorial design

Abstract

Polyurethanes are renowned for their incredible versatility. They are available in various forms, such as foams, thermoplastics, elastomers, and paints. These polymers are synthesized from two chemical substances: isocyanates and polyols. The increasing interest in the utilization of materials from renewable sources has spurred significant research in search of replacements for these two substances. For instance, castor oil can be used as a substitute for polyol, in addition to being an abundant renewable source. In this context, the objective of this study is to investigate how the variables temperature (2 °C, 24 °C, and 70 °C) and mass ratio (2:1, 1:1, and 1:2) influence the final properties of polyurethane foams. The foams were prepared using the one-shot method under controlled agitation. The results indicated that replacing polyol with vegetable oil was successful, as evidenced by the appearance of reference bands in the FTIR spectra. XRD and DSC analyses confirmed the amorphous nature of the polyurethanes, and TG tests demonstrated that a temperature of 70 °C significantly reduced the thermal stability of the foams, especially those based on vegetable sources. However, synthesis temperatures of 2 °C and 24 °C did not show considerable alteration in thermal stability. And the analysis of the effect of the sol fraction variables demonstrated that the polyol/isocyanate ratio has a significant effect, especially in vegetable-based foams.