UV–thermal‐cured cycloaliphatic epoxy composites with enhanced mechanical properties via Ca²⁺‐modified nanocrystalline cellulose

Abstract

UV-thermal-cured cycloaliphatic epoxy resin (CAE) has received great attention due to high curing efficiency, low energy consumption and wide application. However, this rigid polymer with a highly crosslinked network tends to exhibit substantial brittleness. Herein, a novel toughening agent was successfully prepared by modifying nanocrystalline cellulose with Ca 2+ (NCC-Ca). The chemical structure of NCC-Ca was characterized using Fourier transform infrared and X-ray photoelectron spectroscopies. Mechanical properties, moisture absorption and thermal properties of UV-thermal-cured NCC/CAE and NCC-Ca/CAE composites were comprehensively evaluated. With a NCC-Ca content of 0.7 wt%, the impact strength of NCC-Ca/CAE composites was maximized at 5.96 kJ m −2 , while the flexural strength of NCC-Ca/CAE composites with 0.5 wt% of NCC-Ca was maximized at 52.02 MPa. Along with the improvement in mechanical properties, NCC-Ca can also increase the glass transition temperature of CAE composites. Moreover, the toughening mechanism of the NCC-Ca/CAE composites is also discussed.

Synthesis and properties of cycloaliphatic diepoxides containing fluorinated linker

“…ERL-4221 is highly reactive with high T g and is widely used for various applications by thermal curing with hardeners or by photocuring catalyzed by photoacid generators. 13,21,22 Considering the similar cycloaliphatic epoxide structure to ERL-4221, it is reasonable to expect that TCE and OCE will have similar chemical reactivity and can be thermally and photochemically cured. More importantly, they are expected to have improved properties in water resistance and low n d and low D k .…”

“…Our fluorinated CAEs are more flexible, improving some properties that we will discuss later. ERL‐4221 is highly reactive with high T g and is widely used for various applications by thermal curing with hardeners or by photocuring catalyzed by photoacid generators 13,21,22 . Considering the similar cycloaliphatic epoxide structure to ERL‐4221, it is reasonable to expect that TCE and OCE will have similar chemical reactivity and can be thermally and photochemically cured.…”