Study on the Thermal Stability of Urea‐Formaldehyde Resin Microcapsules with Nanosilica Incorporation by Molecular Dynamics Simulation and Experiments

Abstract

It is an innovation to self‐heal the microdefects inside materials by doping microcapsules. Urea‐formaldehyde resin (UF) microcapsule is widely used in self‐healing materials owing to its excellent mechanical properties. However, when it is used in electrical insulation materials, the thermal stability of the microcapsules need to be enhanced owing to the relatively high internal temperature of the material under the long‐term action of electric field. In this paper, molecular dynamics simulation is used to calculate the properties related to the thermal stability of UF microcapsule with and without nanosilica incorporation. The simulation result shows that incorporating nanosilica can increase the density and glass transition temperature, decrease the fractional free volume of UF materials. The UF microcapsules with and without nanosilica incorporation are prepared experimentally, and thermogravimetric test result shows that incorporating nanosilica can enhance the thermal stability of UF microcapsule; scanning electron microscope result shows nanocomposite microcapsule has more UF debris adhered on its surface. By establishing the interface model of UF and nanosilica to explore the internal mechanism, it is found that the interface interaction between UF and nanosilica is conducive to enhancing the thermal stability of UF material.

Investigation of microcapsules based self-healing composites embedded with carbon nanotubes for improved healing efficiency

“…The first stage of mass loss occurred between 150°C and 250°C, which is primarily due to the decomposition of the urea formaldehyde shell material of the microcapsules in all samples except neat epoxy. During the second stage of mass loss between 300°C and 580°C, all the samples underwent a rapid mass loss down to 16 wt.%, which is apparently the thermal decomposition of the base epoxy resin [28,29]. The decomposition temperatures of sample Ep+Mc and neat epoxy for a 10 wt.% residual mass were found to be 682°C and 658°C (ΔT≈24°C), respectively.…”

Self‐lubricating epoxy composite coating with linseed oil microcapsule self‐healing functionality

“…The thermal stability of microcapsules is one of the important indicators to test whether microcapsules can be used in self-lubricating coating, which determines the preservation method and the actual application temperature of microcapsules. 38 The TG curve of the PUF showed a decreasing trend between 35 and 100 C (Figure 4a). The weight loss rate was about 4.48%, which was mainly caused by the evaporation of a small amount of water adsorbed on the PUF.…”

Influence of electric field on moisture-absorbing characteristics at the FRP/RPUF interface: experimental study and molecular dynamics simulation

“…The theory of free volume proposed by Fox and Flory [41,42] suggests that the total volume (V t ) of a polymer is composed of the occupied volume (V o ) and the free volume (V f ). fractional free volume (FFV) is obtained by the ratio of free volume to the total volume of matter, as shown in equation (7) [43,44]. By calculating the free volume of the system, the free volume fraction can be obtained, and the scale factor was set to 0.25 Å.…”