In situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene.

Area of Science:

• Materials Science
• Polymer Chemistry

Background:

• Self-healing materials require microencapsulated agents with robust properties.
• Existing microcapsules often lack sufficient strength, shelf-life, or bonding to host materials.

Purpose of the Study:

• To synthesize urea-formaldehyde (UF) microcapsules containing dicyclopentadiene (DCPD) for self-healing epoxy applications.
• To characterize the microcapsules' properties, including size, morphology, and yield.

Main Methods:

• In situ polymerization of UF in an oil-in-water emulsion to encapsulate DCPD.
• Control of microcapsule size (10-1000 µm) via agitation rate (200-2000 rpm).
• Analysis of surface morphology and shell thickness using optical and electron microscopy; yield and fill content determined by CHN analysis.

Main Results:

• UF microcapsules with DCPD were successfully synthesized, exhibiting a linear relationship between log(mean diameter) and log(agitation rate).
• Microcapsules featured a smooth inner membrane (160-220 nm) and a rough, porous outer surface composed of UF nanoparticles.
• High yields (80-90%) of spherical microcapsules with 83-92 wt% fill content were achieved, influenced by emulsion pH and interfacial area.

Conclusions:

• The developed UF microcapsules meet key requirements for self-healing epoxy systems, including strength, shelf-life, and bonding.
• Agitation rate, pH, and interfacial area are critical parameters for controlling microcapsule characteristics and synthesis efficiency.