The preparation and characterization of polyurethane reinforced with a low fraction of cellulose nanocrystals

Abstract

Cellulose nanocrystals (CNC) produced from renewable cellulosic feedstocks have been used in polymer reinforcement, resulting in significant enhancements to mechanical properties. In this study, a series of CNC reinforced polyurethane (PU) nanocomposites were manufactured and tested for their rheological, thermo-mechanical, mechanical and abrasion properties. First, stable polyol-CNC suspensions were prepared using a combination of water and 1,3-propanediol as dispersing solvent. These suspensions were then combined with isocyanates to produce CNC reinforced PU samples. Rheological testing of the uncured polyol-CNC-isocyanate liquid suspension indicated the formation of a pervading network between CNC particles. The thermo-mechanical properties of the CNC reinforced nanocomposites were significantly improved compared to unreinforced PU, as measured by differential scanning calorimetry and dynamic mechanical analysis. With the addition of 0.5% CNC by weight to the PU resin, the glass transition temperature increased 10 °C. Furthermore, this CNC reinforcement of the PU resin yielded an increase in the tensile strength, Young’s modulus, elongation at break, and abrasion resistance of approximately 30%, 55%, 70%, and 40%, respectively. These increases are likely due to a combination of increased cross-linking density within the PU network, arising from PU-CNC molecular interactions, and the reinforcing effect of the CNC.