Review on Nonconventional Fibrillation Methods of Producing Cellulose Nanofibrils and Their Applications.

The production of cellulose nanofibrils (CNFs) continues to receive considerable attention because of their desirable material characteristics for a variety of consumer applications. There are, however, challenges that remain in transitioning CNFs from research to widespread adoption in the industrial sectors, including production cost and material performance. This Review covers CNFs produced from nonconventional fibrillation methods as a potential alternative solution. Pretreating biomass by biological, chemical, mechanical, or physical means can render plant feedstocks more facile for processing and thus lower energy requirements to produce CNFs. CNFs from nonconventional fibrillation methods have been investigated for various applications, including films, composites, aerogels, and Pickering emulsifiers. Continued research is needed to develop protocols to standardize the characterization (e.g., degree of fibrillation) of the lignocellulosic fibrillation processes and resulting CNF products to make them more attractive to the industry for specific product applications.

Recent Advances in Functional Materials through Cellulose Nanofiber Templating.

Advanced templating techniques have enabled delicate control of both nano- and microscale structures and have helped thrust functional materials into the forefront of society. Cellulose nanomaterials are derived from natural polymers and show promise as a templating source for advanced materials. Use of cellulose nanomaterials in templating combines nanoscale property control with sustainability, an attribute often lacking in other templating techniques. Use of cellulose nanofibers for templating has shown great promise in recent years, but previous reviews on cellulose nanomaterial templating techniques have not provided extensive analysis of cellulose nanofiber templating. Cellulose nanofibers display several unique properties, including mechanical strength, porosity, high water retention, high surface functionality, and an entangled fibrous network, all of which can dictate distinctive aspects in the final templated materials. Many applications exploit the unique aspects of templating with cellulose nanofibers that help control the final properties of the material, including, but not limited to, applications in catalysis, batteries, supercapacitors, electrodes, building materials, biomaterials, and membranes. A detailed analysis on the use of cellulose nanofibers templating is provided, addressing specifically how careful selection of templating mechanisms and methodologies, combined toward goal applications, can be used to directly benefit chosen applications in advanced functional materials.

Material Extrusion Additive Manufacturing of Wood and Lignocellulosic Filled Composites.

Wood and lignocellulosic-based material components are explored in this review as functional additives and reinforcements in composites for extrusion-based additive manufacturing (AM) or 3D printing. The motivation for using these sustainable alternatives in 3D printing includes enhancing material properties of the resulting printed parts, while providing a green alternative to carbon or glass filled polymer matrices, all at reduced material costs. Previous review articles on this topic have focused only on introducing the use of natural fillers with material extrusion AM and discussion of their subsequent material properties. This review not only discusses the present state of materials extrusion AM using natural filler-based composites but will also fill in the knowledge gap regarding state-of-the-art applications of these materials. Emphasis will also be placed on addressing the challenges associated with 3D printing using these materials, including use with large-scale manufacturing, while providing insight to overcome these issues in the future.

Plant Oil-Derived Epoxy Polymers toward Sustainable Biobased Thermosets.

Epoxy polymers (EPs) derived from soybean oil with varied chemical structures are synthesized. These polymers are then cured with anhydrides to yield soybean-oil-derived epoxy thermosets. The curing kinetic, thermal, and mechanical properties are well characterized. Due to the high epoxide functionality per epoxy polymer chain, these thermosets exhibit tensile strength over an order of magnitude higher than a control formulation with epoxidized soybean oil. More importantly, thermosetting materials ranging from soft elastomers to tough thermosets can be obtained simply by using different EPs and/or by controlling feed ratios of EPs to anhydrides.

A biomass approach to mendable bio-elastomers.

Sustainable bioelastomers with high elastic recovery, high resilience and mendability are conceptualized with low chain-entanglement polymers that are predominantly originated from renewable biomass. Polymers with plant oil-derived fatty groups at the side chain were installed with furan, which allowed Diels-Alder addition to introduce dynamic covalent crosslinking. These elastomers are mendable via retro Diels-Alder. Reprocessing of these polymers led to the formation of elastomers with preservation of excellent resilience and elastic recovery.

Biomass Approach toward Robust, Sustainable, Multiple-Shape-Memory Materials.

We report biomass-derived, shape-memory materials prepared via simple reactions, including "grafting from" ATRP and TAD click chemistry. Although the biomass, including plant oils and cellulose nanocrystals, has heterogeneous chemical structures in nature, these materials exhibit excellent multiple shape-memory properties toward temperature, water, and organic solvents, which are comparable to petroleum counterparts. The work presented herein provides burgeoning opportunities to design the next-generation, low-cost, biomass-prevalent, green materials for niche applications.