Monthly Archives: July 2024

New Article: Mechanical and Insulation Performance of Rigid Polyurethane Foam Reinforced with Lignin-Containing Nanocellulose Fibrils

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A new article from Ning Yan’s lab has been published in Polymers written by Kabirat O. Bello and Ning Yan. 

You can find the article here.


Abstract

Isocyanates are critical components that affect the crosslinking density and structure of polyurethane (PU) foams. However, due to the cost and hazardous nature of the precursor for isocyanate synthesis, there is growing interest in reducing their usage in polyurethane foam production—especially in rigid PU foams (RPUF) where isocyanate is used in excess of the stoichiometric ratio. In this study, lignin-containing nanocellulose fibrils (LCNF) were explored as mechanical reinforcements for RPUF with the goal of maintaining the mechanical performance of the foam while using less isocyanate. Different amounts of LCNF (0–0.2 wt.%) were added to the RPUF made using isocyanate indices of 1.1, 1.05, 1.0, and 0.95. Results showed that LCNF served as a nucleating agent, significantly reducing cell size and thermal conductivity. LCNF addition increased the crosslinking density of RPUF, leading to enhanced compressive properties at an optimal loading of 0.1 wt.% compared to unreinforced foams at the same isocyanate index. Furthermore, at the optimal loading, LCNF-reinforced foams made at lower isocyanate indices showed comparable stiffness and strength to unreinforced foams made at higher isocyanate indices. These results highlight the reinforcing potential of LCNF in rigid polyurethane foams to improve insulation and mechanical performance with lower isocyanate usage.

Thank you Professor Zhaohui (Jolene) Tong for your visit

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On Friday July 19th, Professor Tong from Georgia Tech University paid a visit and gave a talk about the various work being done in the Tong Lab.

Dr. Tong has been an Associate Professor and James C. Barber Faculty Fellow in the School of Chemical and Biomolecular Engineering at Georgia Tech since January 2022. She is also the initiative leader in waste valorization in the food-water-energy nexus of the Renewable Bioproduct Institute (RBI). Previously, she served as an assistant and associate professor since 2010 at the University of Florida. She earned her Ph.D. in chemical engineering from Georgia Tech in 2007, followed by work at Ch2M Hill until 2009. Tong’s research focuses on synthesizing functional sustainable materials and catalytical conversion for biochemicals and biofuels from renewable resources. She has published 73 journal papers and 4 patents. Her research has been supported by NSF, USDA, NAS, and DOE. She secured about $5 million in grants after joining Georgia Tech in 2022. Dr. Tong has also served as an associate editor for three journals and held leadership roles in AIChE.

Her talk is summarized below:

Self-assembly of Multiple Functional Biomaterials for Food-Water-Energy Nexus
Bioresource materials such as cellulose, chitin, and lignin, are usually low-cost,
biocompatible, and abundant in nature. The synthesis of functional materials from these
bioresource materials can address long-term challenges in Food-water-Energy Nexus, such as resource and energy depletion, food security, water scarcity, and climate change. However, the adaption of chemical functionalization and self-assembling methodologies to renewable resource materials for functional materials is very challenging due to their macromolecular structures, heterogeneous properties, poor solubility, and the disturbance of impurities. In this talk, we will summarize how we explore self-assembly methods to produce new nanostructures and endure new functions for renewable resource materials. Several examples will be discussed. For example, glycerol, a biowaste from the biodiesel process, has been assembled into a nano-core-shell structure for a smart food packaging film sensor for universal real-time food spoilage monitoring. Biomass waste or cellulose can be assembled as multiple-function controlled-release fertilizers and smart membranes. Ultimately, we would like to use these self-assembly nanostructures from renewable resources to achieve a high-efficiency circular bioeconomy.

Thank you for your informative visit Professor Tong!

New Article: Lignin-based adaptable covalently cross-linked fabric for flexible sensors

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A new article out of a collaboration between Dr. Ning Yan and Dr. Jing Chen’s labs has been published in Materials Chemistry Frontiers written by Xiaozhen Ma, Xiaolin Wang, Honglong Zhao, Minghui Cui, Xiaobo Xu, Fangfang Kong, Peng Chen, Ning Yan, Jin Zhu and Jing Chen.

You can find the article here

Abstract

In this study, we successfully upcycled a novel lignin-based covalent adaptable polyurethane elastomer (LPUE) that we previously synthesized into a graphene-composited covalent adaptable lignin-based polyurethane fabric (LPUF). This fabric exhibited outstanding solvent resistance, toughness (LPUF-0 with a tensile strength of 29.1 ± 1.6 MPa, an elongation at break of 653 ± 67%, and a toughness of 103 ± 3.8 mJ m−3), and deformation responsiveness. These results not only open up new possibilities for improving covalently adaptable networks in fabrics, but also pave the way for developing solvent-resistant, wearable sensing devices.

New Article: A new 3D printing strategy by enhancing shear-induced alignment of gelled nanomaterial inks resulting in stronger and ductile cellulose films

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A new article out of a collaboration between Professor Ning Yan and Dr. Dan Li has been published in the Carbohydrate Polymers Journal written by Yunxia Yang, Dan Li, Ning Yan and Fu Guo.

You can find the article here

Abstract

Cellulose nanofibrils (CNFs) are derived from biomass and have significant potential as fossil-based plastic alternatives used in disposable electronics. Controlling the nanostructure of fibrils is the key to obtaining strong mechanical properties and high optical transparency. Vacuum filtration is usually used to prepare the CNFs film in the literature; however, such a process cannot control the structure of the CNFs film, which limits the transparency and mechanical strength of the film. Here, direct ink writing (DIW), a pressure-controlled extrusion process, is proposed to fabricate the CNFs film, which can significantly harness the alignment of fibrils by exerting shear stress force on the filaments. The printed films by DIW have a compact structure, and the degree of fibril alignment quantified by the small angle X-ray diffraction (SAXS) increases by 24 % compared to the vacuum filtration process. Such a process favors the establishment of the chemical bond (or interaction) between molecules, therefore leading to considerably high tensile strength (245 ± 8 MPa), elongation at break (2.2 ± 0.5 %), and good transparency. Thus, proposed DIW provides a new strategy for fabricating aligned CNFs films in a controlled manner with tunable macroscale properties. Moreover, this work provides theoretical guidance for employing CNFs as structural and reinforcing materials to design disposable electronics.