Scalable processing of thermoplastic polyurethane nanocomposites toughened with nanocellulose

Abstract

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.

Excellent Toughening of 2,6-Diaminopyridine Derived Poly (Urethane Urea) via Dynamic Cross-Linkages and Interfering with Hydrogen Bonding of Urea Groups from Partially Coordinated Ligands

“…Many efforts have been devoted to strengthening and toughening TPU via incorporation of fillers [5,6,7,8,9] and in-situ synthetic methods [10]. Synthesizing TPU with high performance refers to molecular structure and condensed state design that consequentially controls network, soft and hard segments.…”

A cleaner processing approach for cellulose reinforced thermoplastic polyurethane nanocomposites

“…This can be attributed to the improved phase-mixing and interfacial adhesion between nanocrystal and polymer matrix at an optimum NCO/OH ratio, which might cause local resistance for segmental movements of polymer chains and consequently decrease the deformation. [7,58] However, at an off-ratio, the microphase separation might be affected due to poor phase-mixing and causing slippage for creep behavior. [7,59]…”

“…[7,58] However, at an off-ratio, the microphase separation might be affected due to poor phase-mixing and causing slippage for creep behavior. [7,59]…”

“…[22,52] We have previously reported solvent-free reactive extrusion (REX) of TPU nanocomposites using acidhydrolyzed nanocellulose. [7] In our continued effort in cleaner (organic-solvent free) processing of polymer nanocomposites, we aimed to advance this methodology without the use of acid(s) or typical multiple-step acidhydrolysis (including centrifuging, dialysis, ultrasonication, and freeze-drying). Herein, we report a more scalable and cleaner approach for TPU-CNC nanocomposites processing involving the following steps: (i) partial nanonization of microscale cellulose into CNC in deionized water using sonication, (ii) further in situ nanonization and CNC dispersion in polyol through scalable bead-milling, and then (iii) REX of the polyol-CNC dispersion with diisocyanate, and chain extender (Figure 1).…”

Investigation of Nanofibrillated Cellulose for Hydrophobic Packaging Material: Examining Alternatives to Solvent Exchange and Lyophilization

“…Many previous studies have shown the ability of nanocellulose to form aerogels, which are low-density foams derived from a gel-state material (Jin et al 2004). Additionally, many recent studies have investigated the possibility of improving polyurethane foam properties through the addition of nanocellulose (Auad et al 2007;Wik et al 2011;Faruk et al 2013;Amin et al 2016;Lee et al 2016;Ivdre et al 2016;Zhou et al 2016).…”