Influence of palm oil-based polyols on the microstructure and properties of bio-based flexible polyurethane foams

Flexible bio-based polyurethane foams with different content of palm oil-based polyol were prepared. Various characterization techniques including Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), dynamic mechanical analysis (DMA), mechanical testing, and thermogravimetric analysis (TGA) were used to investigate the effects of bio-polyol dosage on microstructure, mechanical properties and thermal properties of the polyurethane foams. There are carbonyl groups in palm oil-based polyol and they can form hydrogen bonds with amino groups. The hydrogen bonds formed between -O- in soft segments and -NH- in hard segments can reduce the degree of microphase separation and the hydrogen bonding index increased from 66.90 to 89.21%, which is consistent to FTIR analysis The DMA results showed that the glass transition temperature (Tg) of the bio-based polyurethane increased with the increase of the content of bio-polyol. Regular cell structure was observed with different content of bio-polyol. When the content of bio-polyol increased from 0 to 45%, the cell size became smaller and decreased from 14.37 to 4.68 mm. The compressive strength of the bio-based polyurethane foams increased. The swelling ratio of the foams decreased from 417.55 to 219.96% as the bio-polyol content increased from 0 to 45%. The hydrogen bonds could provide physical crosslinking points, and improve the strength of the foam.