Photocuring kinetics of UV‐initiated free‐radical photopolymerizations with and without silica nanoparticles

Abstract

We used photodifferential scanning calorimetry to investigate the photocuring kinetics of UV-initiated free-radical photopolymerizations of acrylate systems with and without silica nanoparticles. Two kinetics parameters-the rate constant (k) and the order of the initiation reaction (m)-were determined for hybrid organicinorganic nanocomposite systems containing different amounts of added silica nanoparticles (0 -20 wt %) and at different isothermal temperatures (30 -100°C) using an autocatalytic kinetics model. The kinetic analysis revealed that the silica nanoparticles apparently accelerate the cure reaction and cure rate of the UV-curable acrylate system, most probably due to the synergistic effect of silica nanoparticles during the photopolymerization process. However, a slight decrease in polymerization reactivity that occurred when the silica content increased beyond 15 wt % was attributed to aggregation between silica nanoparticles. We also observed that the addition of silica nanoparticles lowered the activation energy for the UV-curable acrylate system, and that the collision factor for the system with silica nanoparticles was higher than that obtained for the system without silica nanoparticles, indicating that the reactivity of the former was greater than that of the latter.

Conversion and shrinkage analysis of acrylated hyperbranched polymer nanocomposites

“…These were already observed for other acrylate systems, including HBP, 22 and for silica nanocomposites. 19 At the beginning of the reaction, a sharp increase in the rate of polymerization was evident, which corresponded to gelation or autoacceleration. Due to the increasing viscosity, the mobility of the long-chain radical species was reduced; hence, two radical species were less likely to approach each other and recombine.…”

“…[16][17][18][19] Harsch et al 20 found a reduction in conversion of epoxy resin when silica filler was added. In contrast, Cho et al 19 showed that formulations containing silica nanoparticles gave higher ultimate conversion. The latter result would most likely favor shrinkage and stress.…”

Photocuring Behaviors of UV-Curable Perfluoropolyether-Based Fluoropolymers with and without Tertiary Amine

“…This technique is capable of providing photopolymerization kinetics data in which the measured heat flow can be converted directly to the ultimate percentage conversion and polymerization rate for a given formulation, with the data obtained reflecting the overall curing reaction of the sample. However, it should be noted that the cure kinetics data obtained in this study are essentially empirical and do not provide any mechanistic insight [10][11][12].…”

“…Aaccurate kinetics analyses yield quantitative data on the photocuring behaviors of PFPE-based systems for designing new types of MEMS devices [10][11][12].…”

A kinetics study on thein situreversible addition–fragmentation chain transfer and free radical polymerization of styrene in presence of silica aerogel nanoporous particles

“…[24][25] On the other hand, in some studies, an optimum loading of silica nanoparticles has been reported in which the polymerization rate reaches the maximum value. [26][27][28][29] In these studies, silica nanoparticles can improve the mobility and diffusion of propagating radicals, which lead to increase in the rate of polymerization. In this work, the reduction of polymerization rate at higher amount of particles has been attributed to less system stability due to the formation of aggregates.…”