Synthesis and characterization of bio‐based poly(urethane‐urea) nanocomposite coatings employing cellulose nanocrystals incorporated by two different routes

Abstract

During the last decades, the interest in the development of materials fully orpartially biobased has increased. Polyurethanes are extensively used in a widerange of industries because of their versatility. The present work explores thesynthesis of partially biobased poly(urethane-urea) (PUU) composites employing soy-based polyol (SPO) and cellulose nanocrystals (CNC). The latter wereincorporated during the synthesis (in-situ) or after the synthesis (ex-situ). Thepossibility of a technological application as coatings was investigated for thedesigned materials. Polycaprolactone diol was used as a soft segment due tohigh functionality of the soy-based polyol. The physicochemical, thermal andmechanical properties of the prepared matrices were analyzed. Poly(urethaneurea)s containing up to 20% by weight of biobased polyol showed coatingapplication potentiality. Compared to a polycaprolactone-based polyurethane,the utilization of the bioprecursor enhanced light absorption in the UV–Visregion. In addition, partially biobased systems showed better mechanical resistance (Young´s modulus increased up to 6 times) and hydrophobicity (sweelingdecreased from 60 to 8 per cent by weight). Incorporation of cellulose nanocrystals affected primarily the physicochemical and rheological properties ofdispersions. Regarding coating properties, nanocrystals utilization complemented the soy-based polyol improving the performance of the films. Furthermore,the incorporation route affected the dispersions and films properties.