Chemical functionalization of nano fibrillated cellulose by glycidyl silane coupling agents: A grafted silane network characterization study.

Nano fibrillated cellulose (NFC) has turned into a material widely studied due to its desirable performance for numerous organic systems. Nevertheless, its surface is not very compatible with most organic systems; hence, chemical functionalization methods offer a path to solve this problem. In this study, NFC is successfully functionalized with two silane coupling agents: 3-glycidyloxypropyl trimethoxysilane (GPS) and 3-glycidyloxypropyl dimethylethoxysilane (GPMES) by a simple, direct, and environmentally friendly method. Different analyses have been carried out in order to confirm the chemical modification of NFC. ATR-IR, XPS, and 29Si NMR spectroscopies confirmed the chemical modification that allowed the understanding of the structure and the conformation onto the modified NFC surface. SEM and AFM microscopies were performed to study possible alterations in morphology; a slight change was observed. Thermal properties were also analyzed by TGA analysis. It remains stable after chemical functionalization. Grafted NFC showed good performance compared to the pristine one. It allows a better dispersion into organic systems improving their properties.

Morphology and thermal properties of PLA-cellulose nanofibers composites.

Biodegradable nanocomposites were obtained from polylactic acid (PLA) and cellulose nanofibers with diameters ranging from 11 nm to 44 nm. The influence of treated (with 3-aminopropyltriethoxysilane) and untreated nanofibers on the thermal properties of PLA was investigated in detail using multiple session Differential Scanning Calorimetry (DSC) analysis. The nucleating effect of the cellulose nanofibers was confirmed by all the DSC runs (two melting and two crystallization steps). The morphology of both neat PLA and nanocomposites was explored for the first time using a new powerful AFM technique, Peak Force QNM (Quantitative Mechanical Property Mapping at the Nanoscale), which emphasized the nanolevel characteristics by elastic modulus mapping. QNM analyses showed a better dispersion of the silane treated nanofibers in the matrix as compared to the untreated ones. Moreover, a higher degree of crystallinity was detected in the PLA composites containing untreated nanofibers compared to the composites with treated ones.

Gas-phase surface esterification of cellulose microfibrils and whiskers.

A new and highly efficient synthetic method has been developed for the surface esterification of model cellulosic substrates of high crystallinity and accessibility, namely, freeze-dried tunicin whiskers and bacterial cellulose microfibrils dried by the critical point method. The reaction, which is based on the gas-phase action of palmitoyl chloride, was monitored by solid-state CP-MAS (13)C NMR. It was found that the grafting density not only depended on the experimental conditions, but also on the nature and conditioning of the cellulose samples. The structural and morphological modifications of the substrates at various degrees of grafting were revealed by scanning electron microscopy and X-ray diffraction analysis. These characterizations indicated that the esterification proceeded from the surface of the substrate to their crystalline core. Hence, for moderate degree of substitution, the surface was fully grafted whereas the cellulose core remained unmodified and the original fibrous morphology maintained. An almost total esterification could be achieved under certain conditions, leading to highly substituted cellulose esters, presenting characteristic X-ray diffraction patterns.