In situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene.
Microencapsulated healing agents that possess adequate strength, long shelf-life and excellent bonding to the host material are required for self-healing materials. Urea-formaldehyde microcapsules containing dicyclopentadiene were prepared by in situ polymerization in an oil-in-water emulsion that meet these requirements for self-healing epoxy. Microcapsules of 10-1000 microm in diameter were produced by appropriate selection of agitation rate in the range of 200-2000 rpm. A linear relation exists between log(mean diameter) and log(agitation rate). Surface morphology and shell wall thickness were investigated by optical and electron microscopy. Microcapsules are composed of a smooth 160-220 nm inner membrane and a rough, porous outer surface of agglomerated urea-formaldehyde nanoparticles. Surface morphology is influenced by pH of the reacting emulsion and interfacial surface area at the core-water interface. High yields (80-90%) of a free flowing powder of spherical microcapsules were produced with a fill content of 83-92 wt% as determined by CHN analysis.
Brown
E N
EN
Department of Theoretical and Applied Mechanics, University of Illinois at Urbana-Champaign, Talbot Laboratory, IL 61801, USA. en-brown@illinoisalumni.org
Kessler
M R
MR
Sottos
N R
NR
White
S R
SR
D002214:Capsules / Q000627:therapeutic use; D004339:Drug Compounding / Q000379:methods; D004355:Drug Stability; D004655:Emulsions / Q000627:therapeutic use; D005557:Formaldehyde; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007192:Indenes / Q000008:administration & dosage*; D008855:Microscopy, Electron, Scanning / Q000379:methods; D010316:Particle Size; D011208:Powders; D013499:Surface Properties; D014508:Urea; D014945:Wound Healing / Q000187:drug effects
D002214:Capsules; D004655:Emulsions; D007192:Indenes; D011208:Powders; D005557:Formaldehyde; C004689:dicyclopentadiene; D014508:Urea