Improved self-healing properties and crack growth resistance of polydimethylsiloxane elastomers with dual-capsule room-temperature healing systems

Two types of microcapsules were prepared by in situ polymerization with poly(urea-formaldehyde) (PUF) as the shell material. The core materials of the microcapsules contained Sylgard 184A gum (labeled as capsule I) and hydrogen silicone oil (labeled as capsule II). Capsule types I and II were characterized by optical microscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Capsule types I and II were incorporated into silicone rubber polydimethylsiloxane (PDMS) at an appropriate proportion to construct a self-healing system. The healing efficiency initially increases and then decreases with the increased proportion and addition of the two capsules. The maximum self-healing efficiency is obtained with a value of 70.5% by the incorporation of 10 wt% miscellaneous microcapsules when the weight proportion of capsule types II and I is 0.6. Cracks in the PDMS/capsule composites almost disappear with an increased healing time of up to 24 h at room temperature, indicating improved healing properties with a prolonged healing time.