Improved specific thermomechanical properties of polyurethane nanocomposite foams based on castor oil and bacterial nanocellulose

Bacterial nanocellulose (BNC) was used to synthesize polyurethane foams (PUFs) prepared from castor oil polyol and MDI diisocyanate using water as the blowing agent. The BNC reacted with the isocyanate, increasing the weight content of urethane hard segments (HS). It did not behave as a nucleation agent, forming a nanometric distribution of cells within the struts followed by a reduction of the apparent density (-7.6%) and a relevant increase of cell size in the growth direction (+37.9%). An alignment of the BNC parallel to the cell walls was observed, producing a nanocomposite with a higher reinforcement weight fraction in that area. At only 0.2 wt %, the BNC behaved as a nanostructured reinforcement, improving the specific compression modulus and strength by +4.67% and +23.6%, respectively, as well as the thermomechanical properties, with an improvement of the specific E' at 30 degrees C of +52.4%. (C) 2017 Wiley Periodicals, Inc.