Estimation of the mechanical properties of urea–formaldehyde microcapsules by compression tests and finite element analysis

Abstract

Information on the mechanical properties of microcapsules is essential to understanding their performance during manufacturing, processing, and applications. The mechanical properties of urea-formaldehyde (UF) microcapsules filled with ethyl phenyl acetate (EPA) were determined by applying single-microcapsule compression and a finite element model. Microcapsules were prepared by in situ polymerization, and the average wall thickness of microcapsules was 192 6 12 nm as determined using scanning electron microscopy. The deformation behavior of the microcapsule was measured by a single-microcapsule compression experiment between two parallel plates. The results show that both burst deformation and burst force were linearly related to microcapsule size. A model for an elastic shell filled with incompressible fluid was used to simulate compression of the microcapsule in ABAQUS. Dimensionless parameters were introduced to the model. The relationship between dimensionless force and dimensionless displacement depended on the ratio of wall thickness to diameter (e). However, the relationship remained the same when e was less than 1% and can be fitted well by the mathematical equation. An estimation of Young's modulus can be obtained from the compression data for the dimensionless deformation from 10% to 15%. The average Young's modulus of a UF/EPA microcapsule is estimated to be 2.12 6 0.45 GPa.

In situ encapsulation technique for fabrication of self‐healing thermosetting polyurethane with tungsten (VI) chloride

“…Modified in situ polymerization through using oil and water emulsion was achieved in the development of microcapsules 13,30‐32 . First, 0.4 g of sodium dodecyl benzene sulfonate shall be mixed in a double‐walled beaker with a capacity of 800 mL containing 200 mL of deionized water at ambient temperature.…”

“…For measuring fracture toughness and healing efficiency of the composites developed, TDCB samples were brought under tests of controlled fractures. The experiment was carried out on the basis of the notion put forth by White et al 2,32 defining crack healing efficiency, η , as a healed sample capacity to develop fracture toughness 33,34 as Equation (1): …”

Tunable thermal, mechanical, and controlled-release properties of epoxy phenolic novolac resin microcapsules mediated by diamine crosslinkers

“…Overall, the MC shells are soer than previously reported polyurethane or urea-formaldehyde MCs, which is shown by their higher modulus. 38,39 The Young's modulus represents the stiffness of materials and is used to describe their elastic deformation. 40 In this study, the index is strongly linked to the thickness of MC shell.…”

Microcompression Method for Determining the Size-Dependent Elastic Properties of PMMA Microcapsules Containing n-Octadecane

“…Generally, deformation and failure of microencapsulated PCMs (MPCMs) are prone to occur during manufacturing, processing, and applications. − Characterization of the mechanical properties of MPCMs is crucial for evaluating the quality of products . Because PCMs such as n -octadecane can be considered as incompressible liquids, which are not able to withstand shear forces, the mechanical performance of MPCMs mainly depends on the mechanical properties of shells.…”