UV resistance of cellulose nanocrystals/thermoplastic polyurethane nanocomposite

Abstract Polymer composites are often employed in many outdoor applications which expose it to Ultraviolet (UV) radiation. UV exposure to polymer composite resulted in the change of physical, chemical, and mechanical characteristics. Recently, polymers like thermoplastic polyurethane (TPU) have been reinforced with nanofiller like cellulose nanocrystal (CNC) and successfully improve its mechanical properties. However, the effect of UV resistance has not yet been studied. In this work, 1 wt% of CNC hydrolyzed by phosphoric acid was used as reinforcing filler. CNC/TPU nanocomposite films were fabricated through melt extrusion followed by compression molding and subsequently subjected to artificial UV irradiation for 3, 6, 12, and 72 h. Mechanical testing revealed that after 72 h of UV exposure, the tensile strength of neat TPU decreased by 45%, while CNC-reinforced TPU showed a lower reduction of 34%, representing an overall improvement in UV resistance of approximately 24%. Fourier transform infrared (FTIR) spectroscopy indicated that CNC incorporation mitigated photo-oxidative chain scission by preserving hydrogen-bonded N–H and C=O groups, while differential ccanning calorimetry (DSC) analysis showed increased glass transition temperature (T g ) and enthalpy, suggesting CNC-induced structural confinement and UV-triggered crosslinking stabilization. The results confirm that phosphoric-acid-derived CNCs act as an effective reinforcing and UV-shielding nanofiller without compromising transparency, enhancing both mechanical retention and thermal stability under UV aging. Graphical abstract