High heat Resistance, Strength, and toughness of epoxy resin with cellulose nanofibers and structurally designed ionic liquid

This study investigates the synergistic effects of ionic liquid (IL) and nanofillers on the properties of epoxy resin, aiming to address the issues of brittleness commonly associated with commercial epoxy resins. Starting from molecular structural design, a novel ionic liquid containing amino and phenylboronic acid groups is synthesized via a one-step alkylation reaction. The newly synthesized IL is then synergistically combined with cellulose nanofibers (CNFs) to fabricate a series of IL/CNFs epoxy resin composites. The influence of IL/CNFs content on the thermal properties, mechanical performance, glass transition temperature, and transparency of the composite materials is investigated. Compared to pure epoxy resin (EP), the epoxy composite material with 0.5IL-1.0CNFs exhibits a 50.72 % increase in flexural strength, a 126.94 % increase in elongation at break, and a 97.51 % increase in impact strength. In comparison, both the initial and maximum decomposition temperatures increased (T5% was 374 °C, and Tmax was 400 °C), showing an increase of 6 °C and 4 °C, respectively. Additionally, the epoxy composite material maintains high transparency, with a relatively high level of transmittance in the visible light range (400 nm-760 nm). The transmittance at T500nm increases to 86.8 %, and at T400nm it increases to 69.54 % compared to the pure epoxy resin.