Effect of TDI-Assisted Hydrophobic Surface Modification of Microcrystalline Cellulose on the Tensile Fracture of MCC/PLA Composite, and Estimation of the Degree of Substitution by Linear Regression

Designing for Degradation: Transient Devices Enabled by (Nano)Cellulose

Transient technology involves materials and devices that undergo controlled degradation after a reliable operation period. This groundbreaking strategy offers significant advantages over conventional devices based on non-renewable materials by limiting environmental exposure to potentially hazardous components after disposal, and by increasing material circularity. As the most abundant naturally occurring polymer on Earth, cellulose is an attractive material for this purpose. Besides, (nano)celluloses are inherently biodegradable and have competitive mechanical, optical, thermal, and ionic conductivity properties that can be exploited to develop sustainable devices and avoid the end-of-life issues associated with conventional systems. Despite its potential, few efforts have been made to review current advances in cellulose-based transient technology. Therefore, this review catalogs the state-of-the-art developments in transient devices enabled by cellulosic materials. To provide a wide perspective, the various degradation mechanisms involved in cellulosic transient devices are introduced. The advanced capabilities of transient cellulosic systems in sensing, photonics, energy storage, electronics, and biomedicine are also highlighted. Current bottlenecks toward successful implementation are discussed, with material circularity and environmental impact metrics at the center. It is believed that this review will serve as a valuable resource for the proliferation of cellulose-based transient technology and its implementation into fully integrated, circular, and environmentally sustainable devices.

Functionalized cellulose-based adhesive with epoxy groups having high humidity resistance performance

Sustainable and environment friendly natural-based adhesive has been considered as an optimum alternative of industrial adhesive which is non-renewable and harmful to health. Cellulose is the most abundant natural polymer in nature and has potential applications in the field of adhesives. However, the inherent hydrophilic nature of cellulose-based adhesive significantly challenges its use in high humidity environments. In this paper, a highly hydrophobic and anti-swelling cellulose-based adhesive was prepared by epoxy modification of microcrystalline cellulose (MCC). The simultaneous enhancement of adhesive and cohesive properties is achieved through the reaction of epoxy groups with the hydroxyl groups from the wood and adhesive during the hot-pressing process. Prepared adhesive has excellent properties in extremely humid environments. The dry bonding strength of the prepared adhesive reached 6.02 ± 0.26 MPa, while the wet bonding strength was 4.78 ± 0.21 MPa after immersed in water at 63 °C for 3 h. Furthermore, the bonding strength remained largely stable in 90 % atmospheric humidity. The adhesive has a certain universality, which can bond to substrates such as aluminium, iron, and glass. This study presents an innovative approach to the manufacturing of cellulose-based adhesive with enhanced bonding performance and exceptional water resistance.

An examination of recent research of water absorption behavior of natural fiber reinforced polylactic acid (PLA) composites: A review

Researchers have begun focusing on developing biodegradable materials, such as natural fiber/polymer composites (NFPC), since the growing of environmental concerns related to waste management. One crucial aspect that must be established in the development of these composites is their water-absorption behavior. This paper examines the water absorption (WA) behavior of NFPC, with a specific emphasis on natural fiber/polylactic acid (PLA) composites. It discusses processes and numerous aspects related to this behavior, based on recent published research. This review analyzes the influence of several factors, such as the loading of natural fiber, the combination of different natural fibers, the methods used in manufacturing, and the temperature of the water, on the WA behavior of natural fiber/PLA composites. It also explores how WA affects the properties of these composites. In addition, this review also presented techniques for improving the WA resistance of the composites. This review paper provides researchers with insights into the WA behavior of the composites, aiming to facilitate the development of a versatile and eco-friendly material that may effectively address waste disposal challenges.

Functionalisation of lignin with urethane linkages and their strengthening effect on PLA composites

Lignin was functionalised by crosslinking with hexamethylene diisocyanate (HDI) through the heterogenous reaction in the solvent dimethyl sulfoxide for preferential improvement in the mechanical properties of composites. The successful synthesis of lignin modified with HDI was confirmed by the instrumental analyses, e.g., FTIR, XPS, and FESEM. The incorporation of optimum crosslinked lignin in polylactic acid (PLA) matrix was systematically evaluated on the basis of their thermal stability, mechanical property, glass transition temperature (Tg), water contact angle, water absorption, and water permeability. The results displayed that incorporation of fillers had prominent effects on tensile tear strength, which could improve tensile strength up to 231 % and elongation at break up to 53 % due to the good interface compatibility between PLA and modified lignin. Further, with the inclusion of fillers, PLA composites exhibited higher crystallinity in comparison to neat PLA.

Hydrophobic, Sustainable, High-Barrier Regenerated Cellulose Film via a Simple One-Step Silylation Reaction

With the increasing importance of environmental protection, high-performance biopolymer films have received considerable attention as effective alternatives to petroleum-based polymer films. In this study, we developed hydrophobic regenerated cellulose (RC) films with good barrier properties through a simple gas-solid reaction via the chemical vapor deposition of alkyltrichlorosilane. RC films were employed to construct a biodegradable, free-standing substrate matrix, and methyltrichlorosilane (MTS) was used as a hydrophobic coating material to control the wettability and improve the barrier properties of the final films. MTS readily coupled with hydroxyl groups on the RC surface through a condensation reaction. We demonstrated that the MTS-modified RC (MTS/RC) films were optically transparent, mechanically strong, and hydrophobic. In particular, the obtained MTS/RC films exhibited a low oxygen transmission rate of 3 cm³/m² per day and a low water vapor transmission rate of 41 g/m² per day, which are superior to those of other hydrophobic biopolymer films.

Dispersibility Characterization of Cellulose Nanocrystals in Polymeric-Based Composites

Cellulose nanocrystals (CNCs) are hydrophilic nanoparticles extracted from biomass with properties and functions different from cellulose and are being developed for property-oriented applications such as high stiffness, abundant active groups, and biocompatibility. It has broad application prospects in the field of composite materials, while the dispersibility of the CNC in polymers is the key to its application performance. Many reviews have discussed in-depth the modification strategies to improve the dispersibility of the CNC and summarized all characterization for the CNC, but there are no reviews on the in-depth exploration of dispersion characterization. This review is a comprehensive summary of the characterization of CNC dispersion in the matrix in terms of direct observation, indirect evaluation, and quantified evaluation, summarizing how and why different characterization tools reveal dispersibility. In addition, "decision tree" flowcharts are presented to provide the reader with a reference for selecting the appropriate characterization method for a specific composite.

Modification of Cellulose Micro- and Nanomaterials to Improve Properties of Aliphatic Polyesters/Cellulose Composites: A Review

Aliphatic polyesters/cellulose composites have attracted a lot attention due to the perspectives of their application in biomedicine and the production of disposable materials, food packaging, etc. Both aliphatic polyesters and cellulose are biocompatible and biodegradable polymers, which makes them highly promising for the production of “green” composite materials. However, the main challenge in obtaining composites with favorable properties is the poor compatibility of these polymers. Unlike cellulose, which is very hydrophilic, aliphatic polyesters exhibit strong hydrophobic properties. In recent times, the modification of cellulose micro- and nanomaterials is widely considered as a tool to enhance interfacial biocompatibility with aliphatic polyesters and, consequently, improve the properties of composites. This review summarizes the main types and properties of cellulose micro- and nanomaterials as well as aliphatic polyesters used to produce composites with cellulose. In addition, the methods for noncovalent and covalent modification of cellulose materials with small molecules, polymers and nanoparticles have been comprehensively overviewed and discussed. Composite fabrication techniques, as well as the effect of cellulose modification on the mechanical and thermal properties, rate of degradation, and biological compatibility have been also analyzed.