Grafting natural nicotinamide on tempo-oxidized cellulose nanofibrils to prepare flexible and transparent nanocomposite films with fascinating mechanical strength and UV shielding performance

Light pollution from ultraviolet (UV) radiation is gaining growing concerns, as the emissions and burning of fossil fuels destroyed the ozone layer. Seeking a solution against skin exposure to excessive radiation is an urgent requirement. In this study, nicotinamide (NA), the main component of vitamin B3, was introduced as a new modifier into Tempo-oxidized cellulose nanofibrils (TOCNFs) together with the physical cross-linking with tannin acid (TA) to improve anti-UV performance of the nanocomposite films. Incorporation of NA into the films presents distinguished UV shielding capability UVB wavelength range from 200 nm to 320 nm (NTA1-5) due to the introduced functional groups like CO and benzene rings. Moreover, mechanical properties were notably enhanced, which overcome the low strength of common nanocellulosic materials. The stress increased from 69.8 MPa to 116.3 MPa, and the toughness can reach 131.58 MJ/m³ by tuning the additional amount of NA. Meanwhile, TGA and DTG analysis demonstrated that the incorporation of amide bonds and TA into the composite films greatly improved the thermal stability. Thus, the proposed materials fabricated from natural biomolecules show great potential in serving as new kinds of UV-resistant products in the application areas of sunscreen, protective clothing, and building materials.

Facile adjustment on cellulose nanocrystals composite films with glycerol and benzyl acrylate copolymer for enhanced UV shielding property

In the present work, cellulose nanocrystals (CNCs) composite films with suitable applicable capabilities were prepared by facilely incorporating glycerol (Gly) and poly(benzyl acrylate) (PBA). Chemical and morphological variations during the fabrication of the films were systematically characterized. The properties of modified CNCs composite films including UV blocking ability, mechanical strength and thermal properties were characterized to assess their applicable potentials. As a result, the composite films have good UV shielding property in UVC (220-280 nm) region and UVB (280-320 nm) region. The shielding performance of the modified film in the ultraviolet absorption region reached 92.77% to 95.49% respectively, without damaging the original chiral nematic structure of the films. Along with the modification, BACNC film improved the mechanical properties, presenting the tensile strength 16 times higher compared to pure CNCs film. The nanocomposite films proposed in this work showed promising potentials in broad fields, such as food preservation, medical protection, and surface coating applications.