From cellulosic waste to nanocomposites. Part 2: synthesis and characterization of polyurethane/cellulose nanocomposites

Abstract

New polyurethane (PU)-based nanocomposites were synthesized through two-step in situ polymerization by incorporating low loading levels of spherical cellulose nanoparticles (CNs). Structural, mechanical, thermal, and morphological characterization of the nanocomposites was done with infrared spectroscopy, X-ray diffraction, tensile test, dynamic mechanical thermal analysis, thermogravimetry, differential scanning calorimetry, and field emission scanning electron microscopy. The results showed with incorporation of CNs there was no significant change in the structure of PU. However, the addition of 1 % CNs into PU increased the modulus nearly 42 % and tensile strength by 112 %. On the contrary, elongation at break decreased with increasing nanoparticles contents, but the nanocomposites maintained an elongation of greater than 800 %, which was still a large elongation. The thermal stability of PU enhanced with increasing the small amounts of nanoparticles. Also, incorporating of the CNs improved the phase separation between the soft and hard domains which led to an upward shift in melting temperatures and enthalpy of crystalline phase melting. These results were very encouraging in terms of using CNs as an inexpensive nanofiller and improving the mechanical and thermal properties of PU without using solvents in nanocomposite preparation.