Influence of Lactic Acid Surface Modification of Cellulose Nanofibrils on the Properties of Cellulose Nanofibril Films and Cellulose Nanofibril–Poly(lactic acid) Composites

Abstract

In this study, cellulose nanofibrils (CNFs) were modified by catalyzed lactic acid esterification in an aqueous medium with SnCl2 as a catalyst. Films were made from unmodified and lactic acid-modified CNF without a polymer matrix to evaluate the effectiveness of the modification. Ungrafted and lactic acid-grafted CNF was also compounded with poly(lactic acid) (PLA) to produce composites. Mechanical, water absorption, and barrier properties were evaluated for ungrafted CNF, lactic acid-grafted CNF films, and PLA/CNF composites to ascertain the effect of lactic acid modification on the properties of the films and nanocomposites. FTIR spectra of the modified CNF revealed the presence of carbonyl peaks at 1720 cm−1, suggesting that the esterification reaction was successful. Modification of CNF with LA improved the tensile modulus of the produced films but the tensile strength and elongation decreased. Additionally, films made from modified CNF had lower water absorption, as well as water vapor and oxygen permeability, relative to their counterparts with unmodified CNFs. The mechanical properties of PLA/CNF composites made from lactic acid-grafted CNFs did not significantly change with respect to the ungrafted CNF. However, the addition of lactic acid-grafted CNF to PLA improved the water vapor permeability relative to composites containing ungrafted CNF. Therefore, the esterification of CNFs in an aqueous medium may provide an environmentally benign way of modifying the surface chemistry of CNFs to improve the barrier properties of CNF films and PLA/CNF composites.

Assessment and Optimization of Thermal Stability and Water Absorption of Loading Snail Shell Nanoparticles and Sugarcane Bagasse Cellulose Fibers on Polylactic Acid Bioplastic Films

“…A similar inclination was observed in Figure 2 c for thermal stability, where a combination of 99.5 wt.% PLA, and 0.5 wt.% SBCF offered maximum thermal stability of 263 °C, indicating the optimal concentration of PLA and SBCF for higher thermo-physical properties of bioplastic films. These results were consistent with other findings reported elsewhere, where the loading of SBCF was found to improve thermal stability [ 39 , 40 ]. This significant improvement in water absorption rate may be related to the oxidation of the solvent fabricating bioplastic films [ 41 ].…”

Strengthening polylactic acid (PLA) composites with poly(methyl methacrylate)-functionalized cellulose nanofibrils created through grafting-through emulsion polymerization

“…Furthermore, the polymer coating can be tuned to match the desired thermoplastic matrix. For example, PLA, 32,33 poly(ethylene oxide) (PEO), 26 and poly(methyl methacrylate) (PMMA) 25 polymer coatings have been employed to compatibilize CNMs with PLA. However, an ongoing challenge to employ polymer grafted CNMs in practice is developing chemistry that can be performed in the aqueous environment in which CNFs are produced, is compatible with scalable drying techniques in water such as convection and spray drying, and provides a significant improvement in mechanical properties using industrially relevant methods for production and compounding.…”

Application of plasma‐activated silanized cellulose nanofibers in natural rubber composites

“…By improving the bonding ability between CNFs and NR matrix, CNF/NR composites with excellent properties have been prepared by melt blending. [13][14][15][16][17][18] Hosseinmardi et al 19 demonstrated a method to prepare ultra-strong, tear-resistant NR nanocomposites using CNFs modified with lignin nanofibers. Reinforcing latex with 0.1 wt% CNFs compatible with 0.5 wt% lignin resulted in a 256% increase in tear strength and 95% increase in tensile strength.…”

“…The common chemical modification methods are esterification, graft copolymerization, and silanization. By improving the bonding ability between CNFs and NR matrix, CNF/NR composites with excellent properties have been prepared by melt blending 13‐18 …”