The production of strong and elastic polyurethane nanocomposites toughened with nanocellulose and their widespread application in many engineering fields are currently limited by poor processability via classical industrial processing methods and/or the usage of large amount of solvents. In this report, we demonstrate a scalable, organic solvent-free incorporation of nanocellulose into thermoplastic polyurethane (TPU) and a remarkable reinforcement without compromising elastic properties. The nanocomposites were prepared via water-assisted dispersion of nanocellulose in polyether polyol by bead milling, drying and reactive extrusion of this dispersion with 2 comonomers. Upon the incorporation of nanocellulose (0.5 wt. %), as observed from infrared spectroscopic and thermal analysis, the phase mixing of hard and soft-segments in the TPU matrix and the primary relaxation temperature have slightly increased due to the hydrogen bonding, interfacial area and nucleation enhanced by long polar nanocrystals. The TPU/nanocellulose nanocomposites prepared with an appropriate stoichiometric ratio (determined through appropriate process control) showed a remarkable improvement (up to 43 %) in ultimate tensile strength without compromising the elastic properties including elongation, creep and hysteresis.

ARTICLE This journal isThe production of rigid rod-like cellulose nanocrystals (CNC) via more scalable methods is necessitated by an increasing demand for CNC in various industrial sectors over the last few years. Contemporary protocols involve a consumption of large amounts of strong acids, enzymatic treatments, ultra-sonication and combinations thereof. In an attempt to address this scalability challenge, we aimed to isolate CNC via a scalable mechanical method i.e. high energy bead milling (HEBM). An aqueous dispersion of commercially available microcrystalline cellulose (MCC) was micronized through a HEBM process. This process was optimised by varying the concentration (0.5 -2 wt. %) and time (15-60 min) parameters, in order to obtain a high yield of well-separated CNCs as characterised by transmission electron microscopy (TEM). Micronisation of cellulose via the HEBM method under mild conditions resulted in cellulose nanocrystals with an average aspect ratio in the range of 20 to 26. The nanocrystals also retained both their crystallinity index (ICr)(85 to 95 %) and thermal stability described in terms of onset degradation temperature (Tonset)(230 -263 °C). The production yield of CNC from MCC via this process ranged between 57 to 76 %. In addition, we found that micronisation of the MCC in presence of dilute phosphoric acid also resulted in CNC with an average aspect ratio ranging from 21 to 33, high crystallinity (88-90 %) and good thermal stability (Tonset 250 °C). In this study, we demonstrate the micronisation of commercially available MCC into CNC and describe their dimensions and properties after acid treatment and HEBM. Furthermore, we are able to recommend the use of this scalable milling process to produce rod-like cellulose nanocrystals having a thermal stability suitable to withstand the melt processing temperatures of most common thermoplastics.