Encapsulation methods for photo-polymerisable self-healing formulations

Abstract

The aim of this work is to encapsulate a self-healing photo-polymerisable material for aerospace applications. To meet the technical requirements of space applications – low and high temperatures: −120 °C (dark side) to +250 °C (solar side); UV radiations: 200–400 nm; low pressure: 10⁻⁴Pa – we chose trimethylolpropane triacrylate as healing agent. This monomer polymerises at 190 °C. To avoid its earlier thermal polymerisation, an inhibitor was added to the monomer/photo-initiator formulation. Moreover, among several microencapsulation techniques tested, we chose the sol–gel process to form silica microcapsules containing the self-healing formulation. These microcapsules were characterised by different analysis (scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), Fourier transform infra-red spectroscopy (FTIR), etc.) and satisfied our requirements (size 1–30 μm, thermal stability >250 °C). After the microcapsules breakage, the generation of poly(TMPTA) film by radical photopolymerisation of the released TMPTA monomer was proved by disappearance of the IR peak at 1635 cm⁻¹ (assigned to TMPTA). The obtained film has a thermal stability above 300 °C.

Keywords:

• sol–gel
• microencapsulation
• self-healing
• photopolymerisation

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.