How do trees support their upright massive bodies? The support comes from the incredibly strong and stiff, and highly crystalline nanoscale fibrils of extended cellulose chains, called cellulose nanofibers. Cellulose nanofibers and their crystalline parts-cellulose nanocrystals, collectively nanocelluloses, are therefore the recent hot materials to incorporate in man-made sustainable, environmentally sound, and mechanically strong materials. Nanocelluloses are generally obtained through a top-down process, during or after which the original surface chemistry and interface interactions can be dramatically changed. Therefore, surface and interface engineering are extremely important when nanocellulosic materials with a bottom-up process are fabricated. Herein, the main focus is on promising chemical modification and nonmodification approaches, aiming to prospect this hot topic from novel aspects, including nanocellulose-, chemistry-, and process-oriented surface and interface engineering for advanced nanocellulosic materials. The reinforcement of nanocelluloses in some functional materials, such as structural materials, films, filaments, aerogels, and foams, is discussed, relating to tailored surface and/or interface engineering. Although some of the nanocellulosic products have already reached the industrial arena, it is hoped that more and more nanocellulose-based products will become available in everyday life in the next few years.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202002264

Surface and Interface Engineering for Nanocellulosic Advanced Materials.

Lignocellulosic fibers and lignin are two of the most important natural bioresources in the world. They show tremendous potential to decrease energy utilization/pollution and improve biodegradability by replacing synthetic fibers in bioplastics. The compatibility between the fiber-matrix plays an important part in the properties of the bioplastics. The improvement of lignocellulosic fiber properties by most surface treatments generally removes lignin. Due to the environmental pollution and high cost of cellulose modification, focus has been directed toward the use of lignocellulosic fibers in bioplastics. In addition, lignin-reinforced bioplastics are fabricated with varying success. These applications confirm there is no need to remove lignin from lignocellulosic fibers when preparing the bioplastics from a technical point of view. In this review, characterizations of lignocellulosic fibers and lignin related to their applications in bioplastics are covered. Then, we generalize the developments and problems of lignin-reinforced bioplastics and modification of lignin to improve the interaction of lignin-matrix. As for lignocellulosic fiber-reinforced bioplastics, we place importance on the low compatibility of the lignocellulosic fiber–matrix. The applications of lignin-containing cellulose and lignocellulosic fibers without delignification in the bioplastics are reviewed. A comparison between lignocellulosic fibers and lignin in the bioplastics is given.

Applications of Lignocellulosic Fibers and Lignin in Bioplastics: A Review

Challenges and new opportunities on barrier performance of biodegradable polymers for sustainable packaging

Thermal properties of nanocellulose-reinforced composites: A review

The demand for sustainable functional materials with an eco-friendly preparation process is on the rise. Lignocellulosics has been attributed as the most sustainable bioresource on earth which can meet the stringent requirements of functionalization. However, cellulose nanomaterials obtained from lignocellulosics which has reached advanced stages as a sustainable functional material is challenged by its preparation procedures. These procedures cannot best be described as sustainable and eco-friendly owning to lots of energy and chemicals spent in the pre-treatment and purification processes. These processes are intended to aid fractionation into the major components in order to remove lignin and hemicellulose for the production of cellulose nanomaterials. This work is thus centred on reviewing the progress achieved in introducing a new cellulose nanomaterial containing lignin. The preparation processes, properties and applications of this new lignin-containing cellulose nanomaterial will be discussed in order to chart a sustainable preparation route for cellulose nanomaterials.

Lignin-Containing Cellulose Nanomaterials: A Promising New Nanomaterial for Numerous Applications

Lignin, the second most abundant natural polymer on earth after cellulose, contains both hydrophilic and hydrophobic groups. In this study, the use of nanocellulose fibrils with high lignin content (NCFHL) has been explored to make polylactic acid (PLA) biocomposites with excellent mechanical, thermal, and barrier properties. Different amounts of NCFHL aqueous suspensions (5–20 wt %) were wet mixed with PLA latex to form composite films by casting and hot pressing. The presence of lignin imparted a strong compatibility between NCFHL and the PLA matrix, which overcame the major issue of poor interfacial bonding associated with nanocellulose fibrils without lignin previously reported by literature studies. Atomic force microscope infrared spectroscopy (AFM-IR) characterization results showed an effective coupling between NCFHL and PLA at the nanoscale. With 5–10 wt % of NCFHL additions to the PLA matrix, a significant improvement in mechanical, thermal, and water vapor barrier properties was observed for th...

Polylactic Acid Biocomposites Reinforced with Nanocellulose Fibrils with High Lignin Content for Improved Mechanical, Thermal, and Barrier Properties

Investigating the effect of lignin on the mechanical, thermal, and barrier properties of cellulose nanofibril reinforced epoxy composite

Thermally stable, enhanced water barrier, high strength starch bio-composite reinforced with lignin containing cellulose nanofibrils.

Lignin containing cellulose nanofibril application in pMDI wood adhesives for drastically improved gap-filling properties with robust bondline interfaces

In this work, the use of microsized cellulosic particles obtained from spray dried cellulose nanofibrils with high lignin content (>20 wt %) were explored for the first time as reinforcement in polypropylene (PP) composites. Their effect was compared with the results from PP composites reinforced by cellulosic particles of spray dried cellulose nanofibrils with a low lignin content (<5 wt %). Cellulose nanofibrils with diameters less than 100 nm were obtained by mechanically fibrillating unbleached and bleached cellulosic fibers obtained from tree bark after alkaline extraction for removal of extractive. These cellulose nanofibrils were then spray dried to microsized high lignin content cellulose particles (HLCP) and low lignin content cellulose particles (LLCP), respectively. The presence of a large amount of lignin in the nanofibrils alleviated the degree of aggregation during the spray drying process. Both HLCP and LLCP were melt compounded with polypropylene (PP) to make composites films with differen...

Effects of Lignin Content on Mechanical and Thermal Properties of Polypropylene Composites Reinforced with Micro Particles of Spray Dried Cellulose Nanofibrils

Heyu Chen

Papers

Polylactic Acid Biocomposites Reinforced with Nanocellulose Fibrils with High Lignin Content for Improved Mechanical, Thermal, and Barrier Properties

Investigating the effect of lignin on the mechanical, thermal, and barrier properties of cellulose nanofibril reinforced epoxy composite

Thermally stable, enhanced water barrier, high strength starch bio-composite reinforced with lignin containing cellulose nanofibrils.

Lignin containing cellulose nanofibril application in pMDI wood adhesives for drastically improved gap-filling properties with robust bondline interfaces

Effects of Lignin Content on Mechanical and Thermal Properties of Polypropylene Composites Reinforced with Micro Particles of Spray Dried Cellulose Nanofibrils