Influence of synthesis parameters on properties and characteristics of poly (urea-formaldehyde) microcapsules for self-healing applications

Abstract

Poly(urea-formaldehyde) (PUF) microcapsules filled with dicyclopentadiene (DCPD) were prepared by in situ polymerisation and the effect of synthesis parameters, such as pH of the solution and agitation rate, on microcapsules size and shell thickness was evaluated. Scanning electron microscopy (SEM) and Fourier transform infra-red spectroscopy (FTIR) were performed. Adjusted pH conditions (pH = 3.5) and agitation rate (1350 RPM) were found using a design of experiments (DOE). SEM results indicated that microcapsule size was directly affected by agitation rate, whereas shell thickness was mostly affected by pH. After obtaining adjusted synthesis conditions, microcapsules presenting mean size of 60 µm and mean shell thickness of 4 µm were embedded in an epoxy matrix for evaluating the self-healing effect. FTIR and SEM analyses in damaged samples suggested that a healing agent was delivered to the crack location.

Keywords:

• Microcapsules
• in situ polymerisation
• poly(urea-formaldehyde)
• factorial design
• self-healing

Acknowledgements

The authors thank the following Brazilian institutions for financial support: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001 and Programa de Pós-Graduação em Ciência e Engenharia de Materiais (PPGCEM-UFRN). The authors would like to acknowledge LEPCom-UFMG for the use of the infra-red microscope equipment.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by the Brazilian funding CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) [Brasil (CAPES) - Finance Code 001]. The authors would like to express their thanks.