Heterogeneous Epoxidation of Microcrystalline Cellulose and the Toughening Effect toward Epoxy Resin

Abstract

Microcrystalline cellulose (MCC) is regarded as a potential filler in the fabrication of epoxy composites. However, MCC’s hydrophilic nature and strong hydrogen bonds caused by abundant surface hydroxyl groups greatly weaken its compatibility with the epoxy resin. In addition, it remains a challenge to efficiently and heterogeneously modify MCC surface hydroxyl groups. In this work, MCC was epoxidized heterogeneously with a phase-transfer catalyst. Results indicated that 4.48% (by mass) or 58.15% (by coverage) of the hydroxyl groups on MCC was modified. The dispersibility of epoxidized MCC (EP-MCC) in the epoxy resin was significantly improved. At the same time, EP-MCC showed the ability to interact with the epoxy network covalently, improving the interface interactions, indicating the simultaneous enhancement of the modulus and the toughness. As a result, this heterogenous epoxidation method showed high efficiency in reducing the surface hydroxyl content of MCC, endowing it with a bright future in industrial applications of epoxy composites.

Fluorescent Patterning of Polymeric Substrates with Rare-Earth-Doped Nanophosphors Assisted by Atmospheric Pressure Plasma

“…Besides, all samples have similar spectral features (Figure b), inferring the presence of the same functional groups. Specifically, the broad band in the 3200–3700 cm –1 region as well as the relatively narrow band at 1650 cm –1 is indexed to the O–H vibration . The bands at 1410 and 1007 cm –1 are attributed to the carbonyl groups that originated from the acetylacetonate residues or the CO 2 absorption from the atmosphere .…”

“…Specifically, the broad band in the 3200−3700 cm −1 region as well as the relatively narrow band at 1650 cm −1 is indexed to the O−H vibration. 23 The bands at 1410 and 1007 cm −1 are attributed to the carbonyl groups that originated from the acetylacetonate residues or the CO 2 absorption from the atmosphere. 24 The peaks at 832 and 703 cm −1 are likely to be responsible for the trace of Y(Eu, Tb)−OH, while the peak at 564 cm −1 corresponds to Y(Eu, Tb)−O symmetric stretching mode.…”

Study on improving the toughness of rapidly curing epoxy resin composite materials with a biobased microcrystalline cellulose

“…Microcrystalline cellulose is a high‐crystallinity cellulose powder material obtained after the natural plant fiber is hydrolyzed by acid or alkali and the amorphous part is removed. It has a certain length‐diameter ratio, higher modulus and mechanical strength, good fluidity, and can be dispersed in the polymer resin matrix 19–21 …”

“…It has a certain length-diameter ratio, higher modulus and mechanical strength, good fluidity, and can be dispersed in the polymer resin matrix. [19][20][21] This study explored a rapid curing process that only required the combination of resin and curing agent without adding other accelerators. The curing system used in this paper is the widely used, inexpensive, and readily available epoxy resin (WSR618) and the transparent, colorless, and less toxic 593 curing agent, which cures at room temperature.…”

Novel Multifunction Epoxy Thermoset Designed by Manipulating the Silicon-Oxidation Flexible-Rigid Network Topology: Toughening, Strengthening, and Acid/Alkali Resistance

“…Thermosetting epoxy resins (EPs) and their composites are widely used in various fields, such as aerospace, automotive, and construction, owing to their good strength, heat resistance, and dimensional stability. – Their superior performances are attributed to the presence of covalently cross-linked networks. – However, the structure of the cross-linked network is hard to control, leading to difficulties in regulating properties, such as strength, toughness, corrosion resistance, and thermal properties, and overcoming the inherent strength–toughness trade-off. , Generally, the highly rigid cross-linked structures make it difficult for thermosetting resins to dissipate internal stress caused by various applied loads, allowing the formation and evolution of cracks during use and finally resulting in the permanent failure of materials. , Considering the nonrecyclability of thermosetting materials, this problem shortens their service life and is not conducive to the safe use and sustainable development of EPs . Therefore, constructing and regulating cross-linked networks that couple hardness with softness to achieve controllable properties and overcome the trade-off effect between strength and toughness are the biggest difficulties faced in the development of EPs.…”