Enhancement of thermal and mechanical properties of waterborne polyurethane-urea via chitin nanocrystal reinforcement

Abstract

[EN] Chitin nanocrystals (ChNC) have attracted significant interest as reinforcement due to their exceptional me chanical properties such as Young's modulus, surface functional groups that promote hydrogen-bonding in teractions with specific matrices, and high length/diameter aspect ratio. Therefore, this study investigated the incorporation of chitin nanocrystals into a waterborne polyurethane urea dispersion (WBPUU) at concentrations ranging from 0.5 to 7 wt%. Nanocomposite films were prepared using an ultra-sonication assisted solvent casting method, and their properties were thoroughly analysed. The results demonstrate that the addition of ChNC significantly enhances thermomechanical stability, Young's modulus and stress at break, achieving the percolation threshold at a theoretical concentration of 3 wt% of ChNC. Notably, beyond the percolation threshold, these properties have increased significantly up to WBPUU7, with thermomechanical stability improving by more than 500 % and both Young's modulus and stress at break increasing by over 100 % when compared to values obtained at WBPUU. The study revealed that the addition of ChNC significantly influences water absorption, resulting in a fourfold increase in uptake in a basic medium. Furthermore, the abrasion esistance of the nanocomposites improves with ChNC content due to stable and interconnected network forms.Financial support from the Basque Country Government in the frame of Grupos Consolidados (IT-1690-22) is gratefully acknowledged. The authors also acknowledge the Macrobehavior-Mesostructure-Nanotechnology SGIker unit from the University of the Basque Country (UPV/EHU). Andrea Ugarte would like to thank the University of the Basque Country (UPV/EHU) and Tecnalia Research and Innovation Centre for the PhD grant PIFTEC22-12