Assessing the Flexural Properties of Epoxy Composites with Extremely Low Addition of Cellulose Nanofiber Content

Yingmei Xie,Ryugo Ishigami,Fumio Narita,Hiroki Kurita

doi:10.3390/app10031159

Abstract

Epoxy resins are a widely used common polymer due to their excellent mechanical properties. On the other hand, cellulose nanofiber (CNF) is one of the new generation of fibers, and recent test results show that CNF reinforced polymers have high mechanical properties. It has also been reported that an extremely low CNF addition increases the mechanical properties of the matrix resin. In this study, we prepared extremely-low CNF (~1 wt.%) reinforced epoxy resin matrix (epoxy-CNF) composites, and tried to understand the strengthening mechanism of the epoxy-CNF composite through the three-point flexural test, finite element analysis (FEA), and discussion based on organic chemistry. The flexural modulus and strength were significantly increased by the extremely low CNF addition (less than 0.2 wt.%), although the theories for short-fiber-reinforced composites cannot explain the strengthening mechanism of the epoxy-CNF composite. Hence, we propose the possibility that CNF behaves as an auxiliary agent to enhance the structure of the epoxy molecule, and not as a reinforcing fiber in the epoxy resin matrix.

Highlights

Epoxy resins are widely used in adhesives, coatings, electronics, sporting goods, and aerospace applications, owing to their excellent properties of being a polymeric material with high strength, stiffness, temperature resistance, dimensional stability, and fatigue resistance [1]
The tendency was that the flexural modulus and strength of the epoxy resin were by a Cellulose nanofiber (CNF) addition, while the fracture elongation of the epoxy resin decreased with CNF addition
Epoxy-CNF composites were prepared with an extremely-low CNF (~0.44 vol.%) via a high

Summary

Introduction

Epoxy resins are widely used in adhesives, coatings, electronics, sporting goods, and aerospace applications, owing to their excellent properties of being a polymeric material with high strength, stiffness, temperature resistance, dimensional stability, and fatigue resistance [1]. Cellulose nanofiber (CNF) is a large aspect ratio, string-like, sustainable material, which is highly crystalline and consists of transversely-filled long cellulose molecules linked by strong hydrogen bonds. It is well-known that the long cellulose molecules are incorporated into the cell walls of higher plants, such as hemicellulose and lignin [2,3]. Lu et al dispersed modified CNF using silane and titanate coupling agents in acetone and reported an increase of storage modulus from 2.59 to 3.45 GPa at 30 ◦ C, with a nanocellulose content of 5 wt.% [4]. Omrani et al discussed the effects of cellulose on the curing behavior and properties and suggested that a nanocellulose content of 0.5 phr (per hundred resin)

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Conclusion