The Mechanical Properties Relationship of Radiation-Cured Nanocomposites Based on Acrylates and Cationic Polymerized Epoxies and the Composition of Silane-Modified Tungsten Disulfide Nanoparticles

Abstract

The effect of semiconducting tungsten disulfide (WS2) nanoparticles (NPs), functionalized by either methacryloxy, glycidyl, vinyl, or amino silanes, has been studied in photocuring of acrylate and epoxy resins (the latter photocured according to a cationic mechanism). The curing time, degree of curing (DC), thermal effects, and mechanical properties of the radiation-cured resins were investigated. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analyses confirmed that a silane coating was formed (1–4 nm) on the NPs’ surface having a thickness of 1–4 nm. Fourier transition infrared (FTIR) was used to determine the DC of the nanocomposite resin. The curing time of the epoxy resin, at 345–385 nm wavelength, was 10 to 20 s, while for acrylate, the curing time was 7.5 min, reaching 92% DC in epoxy and 84% in acrylate. The glass transition temperature (Tg) of the photocured acrylates in the presence of WS2 NPs increased. In contrast to the acrylate, the epoxy displayed no significant variations of the Tg. It was found that the silane surface treatments enhanced the DC. Significant increases in impact resistance and enhancement in shear adhesion strength were observed when the NPs were treated with vinyl silane. A previous study has shown that the addition of WS2 NPs at a concentration of 0.5 wt.% is the optimal loading for improving the resin’s mechanical properties. This study supports these earlier findings not only for the unmodified NPs but also for those functionalized with silane moieties. This study opens new vistas for the photocuring of resins and polymers in general when incorporating WS2 NPs.

Accelerated Photocuring of Acrylate Resins with WS2 Nanoparticles

“…This unexpected phenomenon must be further investigated, e.g., by varying the film thickness systematically. Figure S5 displays the DoC of the neat acrylate and the acrylate with WS 2 NPs as a function of time measured for the sample exposing first the front and then the backside of the film . It can be noticed that the DoC of the front side is larger than that of the backside, which is attributed to the lower illumination intensity of the backside by the reflective mirror.…”

“…Figure S5 displays the DoC of the neat acrylate and the acrylate with WS 2 NPs as a function of time measured for the sample exposing first the front and then the backside of the film. 36 It can be noticed that the DoC of the front side is larger than that of the backside, which is attributed to the lower illumination intensity of the backside by the reflective mirror. Furthermore, the addition of the WS 2 NPs accelerated the conversion rate for both the front and back sides.…”

“…This also means that using a short light pulse, the photocuring process can be confined to the size of the NPs, which can be made as small as a few nm. Preliminary results on the enhanced photocuring kinetics of acrylate films using surface-modified IF-WS 2 NPs of acrylates have been reported recently . In the present article, pristine IF-WS 2 NPs were studied, which permitted a detailed mechanistic study of their photocuring kinetics and comparison with a commercial PI.…”

“…Preliminary results on the enhanced photocuring kinetics of acrylate films using surface-modified IF-WS 2 NPs of acrylates have been reported recently. 36 In the present article, pristine IF-WS 2 NPs were studied, which permitted a detailed mechanistic study of their photocuring kinetics and comparison with a commercial PI. In order to understand the acceleration effect of the NPs and elucidate the photocuring mechanism, a series of electron paramagnetic resonance (EPR) measurements as well as other analyses were carried out.…”