Tuning the Nanoscale Properties of Phosphorylated Cellulose Nanofibril-Based Thin Films To Achieve Highly Fire-Protecting Coatings for Flammable Solid Materials

• Published in: ACS applied materials & interfaces Vol. 10; no. 38; pp. 32543 - 32555
• Main Authors: Ghanadpour, Maryam, Carosio, Federico, Ruda, Marcus C, Wågberg, Lars
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 26.09.2018
• Subjects: Cellulose; Cellulose films; Cellulose nanofibrils; Cellulose nanofibrils (CNFs); Coatings; Elastic moduli; Film preparation; Flame retardants; flame-retardant; Flammable materials; Flammable solids; Fourier transform infrared spectroscopy; Montmorillonite (MMT); nanocomposite; Nanocomposite films; Nanocomposites; Nanofibers; Nanoscale properties; phosphorylated cellulose nanofibrils; Phosphorylation; Polymer films; Semiconducting films; Shielding properties; Sodium compounds; Sodium hexametaphosphate; Structural feature; Tensile strength; thermal stability; Thermodynamic stability; Thermogravimetric analysis; thin film; Thin films; Ultrathin films; nanocomposite; thin film; thermal stability; phosphorylated cellulose nanofibrils; flame-retardant
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/acsami.8b10309

Ultrathin nanocomposite films were prepared by combining cellulose nanofibrils (CNFs) prepared from phosphorylated pulp fibers (P-CNF) with montmorillonite (MMT), sepiolite (Sep) clay, or sodium hexametaphosphate (SHMP). The flame-retardant and heat-protective capability of the prepared films as casings for a polyethylene (PE) film was investigated. Heating the coated PE in air revealed that the polymer film was thoroughly preserved up to at least 300 °C. The P-CNF/MMT coatings were also able to completely prevent the ignition of the PE film during cone calorimetry, but neither the P-CNF/Sep nor the P-CNF/SHMP coating could entirely prevent PE ignition. This was explained by the results from combined thermogravimetry Fourier transform infrared spectroscopy, which showed that the P-CNF/MMT film was able to delay the release of PE decomposition volatiles and shift its thermal degradation to a higher temperature. The superior flame-retardant performance of the P-CNF/MMT films is mainly attributed to the unique compositional and structural features of the film, where P-CNF is responsible for increasing the char formation, whereas the MMT platelets create excellent barrier and thermal shielding properties by forming inorganic lamellae within the P-CNF matrix. These films showed a tensile strength of 304 MPa and a Young’s modulus of 15 GPa with 10 wt % clay so that this composite film was mechanically stronger than the previously prepared CNF/clay nanopapers containing the same amount of clay.