Curing and morphology approaches of polyurethane/poly(ethylene glycol) foam upon poly(lactic acid) addition

The effect of poly(lactic acid) (PLA) content on the curing of polyethylene glycol (PEG) based polyurethanes (PU) was investigated. Aiming to produce biobased PU foams, pentamethylene diisocyanate (PDI) was used. Fourier transform infrared spectroscopy (FTIR) found no curing evidence at 30°C and verified that the curing was completed at 300°C. This method tracks hydrogen bonding and NCO consumption. PLA addition decreased the curing rate as evidenced through differential scanning calorimetry (DSC) and promoted changes in the released heat which is linked to chemical and physical crosslinking. Complex peaks were verified in DSC scans whereas the peak at lower temperatures is related to the catalyzed curing while that in the higher ones is due to the homopolymerization. PU foams morphology was investigated using scanning electron microscopy (SEM). Pores and cell sizes are related to PLA content and hydrogen bonding.