Multifunctional pectin and lignin-containing cellulose nanofiber films with improved UV resistance and mechanical properties

Abstract

This study aimed to study the real-time interaction of apple pectin and LCNF using Quartz crystal microbalance with dissipation monitoring (QCM-D) to understand the compositional factors that influence their film formation and assess the impact of varying polymer ratios (0-100%) on the UV resistance, hydrophobicity, and mechanical properties of resulting composite films. Results revealed that apple pectin forms partially irreversible interaction with LCNF, evidenced by a frequency change of 14.9 Hz after the final rinsing stage. This finding was supported by FTIR of the composite films, demonstrated by a shift of the broader -OH stretching vibration at 3325 cm-1 to 3302 cm-1 due to the formation of strong hydrogen bonding. LCNF-based films (LCNF >50%) were less soluble in water compared to pectin-based films (pectin >50%) due to less permeable structure and hydrophobic lignin which interferes in hydrogen bonding with water. Pectin-based films displayed high transparency (%Transmittance >89% at 650 nm) and lower hydrophobicity. Due to the presence of lignin chromophores, the UV shielding property was the highest for LCNF-based films as it almost completely shielded the UV spectrum (%T ∼0 at 320 nm). The reinforcement provided by LCNF significantly enhanced the mechanical properties of the films. Consequently, this study offers valuable insights into the real-time interaction dynamics between apple pectin and LCNF, facilitating the development of biocomposite films with versatile properties that hold significant promise for a wide range of applications.