Preparation and characterization of poly(urea-formaldehyde) microcapsules filled with epoxy resins

Abstract The preparation of microcapsules applied to the fabrication of self-healing composites has been paid more attentions. A new series of microcapsules were prepared by in situ polymerization technology with poly(urea-formaldehyde) (PUF) as a shell material and a mixture of epoxy resins (diglycidyl ether of bisphenol A: DGEBPA) and 1-butyl glycidyl ether (BGE) as core materials. The microencapsulating process of core material was monitored using optical microscopy (OM). The chemical structure of microcapsule was characterized using Fourier-transform infrared spectroscopy (FTIR). Morphology and shell wall thickness of microcapsule were observed using metalloscope (MS), scanning electron microscopy (SEM) and OM, respectively. The effects of different pre-polymers, weight ratios of urea to formaldehyde (U–F) and the agitation rates on the physical properties of microcapsules were investigated. The storage stability of microcapsules at different times and temperatures was analyzed. The thermal properties of microcapsules were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results indicate that PUF microcapsules containing epoxy resins can be synthesized successfully, and during the microencapsulation, the epoxide rings in epoxy resins are hardly affected by the surrounding media. The rough outer surface of microcapsule is composed of agglomerated PUF nanoparticles. The size and surface morphology of microcapsule can be controlled by selecting different processing parameters. The microcapsules basically exhibit good storage stability at room temperature, and they are chemically stable before the heating temperature is up to approximately 238 °C.

[1]  N. Sottos,et al.  Self-healing structural composite materials , 2003 .

[2]  Qian Yu,et al.  Development of an immobilization method by encapsulating inorganic metal salts forming hollow microcapsules , 2005 .

[3]  M. Yúfera,et al.  Food microparticles for larval fish prepared by internal gelation , 2005 .

[4]  H. Mahabadi,et al.  Interfacial polymerization encapsulation of a viscous pigment mix: emulsification conditions and particle size distribution. , 1991, Journal of microencapsulation.

[5]  M. Sasaki,et al.  Improved survival and ammonia metabolism by intraperitoneal transplantation of microencapsulated hepatocytes in totally hepatectomized rats. , 2001, Surgery.

[6]  Henry Lee,et al.  Handbook of Epoxy Resins , 1967 .

[7]  G. Simon,et al.  Phosphorus-containing diamine for flame retardancy of high functionality epoxy resins. Part II. The thermal and mechanical properties of mixed amine systems , 2006 .

[8]  Roberto J. J. Williams,et al.  Curing reaction of epoxy resins with diamines , 1984 .

[9]  L. Matějka,et al.  Crosslinking of epoxy-polysiloxane system by reactive blending , 2004 .

[10]  H. Herma,et al.  Amino resin microcapsules. I. Literature and patent review , 1989 .

[11]  N. Sottos,et al.  In situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene , 2003 .

[12]  K. Sawada,et al.  Preparation of photosensitive color-producing microcapsules utilizing in situ polymerization method , 2005 .

[13]  Geoffrey Ingram Taylor,et al.  The Viscosity of a Fluid Containing Small Drops of Another Fluid , 1932 .

[14]  C. Macosko,et al.  Homogeneous reactive coupling of terminally functional polymers , 2001 .

[15]  Jiyoung Oh,et al.  Microcapsules as an electronic ink to fabricate color electrophoretic displays , 2005 .

[16]  J. Baselga,et al.  Confocal microscopy study of phase morphology evolution in epoxy/polysiloxane thermosets , 2005 .

[17]  N. Yan,et al.  13C NMR study on structure, composition and curing behavior of phenol–urea–formaldehyde resole resins , 2004 .

[18]  J. Watts,et al.  The use of high-resolution XPS and ToF-SIMS to investigate segregation phenomena of minor components of a model coil coating formulation , 1998 .

[19]  P. Pearce,et al.  Rubber toughening of practical tetraglycidyl methylenedianiline-piperidine adduct systems , 1996 .

[20]  P. Pearce,et al.  Aspects of Latency in Epoxy Film Adhesives , 1992 .

[21]  Takao Yamamoto,et al.  An approach to analysis of pigment release from microcapsules with size distribution , 2002 .

[22]  N. Sottos,et al.  Autonomic healing of polymer composites , 2001, Nature.

[23]  Thomas J. Pinnavaia,et al.  Clay-Polymer Nanocomposites Formed from Acidic Derivatives of Montmorillonite and an Epoxy Resin , 1994 .

[24]  T Niwa,et al.  Preparation of controlled-release microspheres of ibuprofen with acrylic polymers by a novel quasi-emulsion solvent diffusion method. , 1990, Journal of pharmaceutical sciences.

[25]  N. Sottos,et al.  In situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene , 2003, Journal of microencapsulation.

[26]  M. Frenkel,et al.  The formation of a three dimensional network structure in cured urea-formaldehyde oligomers , 1979 .

[27]  R. Singhal,et al.  Microencapsulation of cardamom oleoresin: Evaluation of blends of gum arabic, maltodextrin and a modified starch as wall materials , 2005 .

[28]  P. Mishra,et al.  Dual coated erodible microcapsules for modified release of diclofenac sodium. , 2004, European journal of pharmaceutics and biopharmaceutics : official journal of Arbeitsgemeinschaft fur Pharmazeutische Verfahrenstechnik e.V.

[29]  Hailiang Zhang,et al.  Studies on the properties of a new hybrid materials containing chain-extended urea and SiO2–TiO2 particles , 2005 .

[30]  G. Camino,et al.  Mechanism of thermal degradation of urea-formaldehyde polycondensates , 1983 .

[31]  Xiaopeng Zhao,et al.  Preparation of a kind of red encapsulated electrophoretic ink , 2004 .

[32]  S. Bourbigot,et al.  Microencapsulation of phosphate: application to flame retarded coated cotton , 2002 .

[33]  Sabu Thomas,et al.  Hydroxyl terminated poly(ether ether ketone) with pendent methyl group toughened epoxy resin: miscibility, morphology and mechanical properties , 2005 .

[34]  Bryan Ellis,et al.  Chemistry and technology of epoxy resins , 1992 .

[35]  L. Dobetti,et al.  Application of a hydrodynamic model to microencapsulation by coacervation , 2002, Journal of microencapsulation.

[36]  C. Perruchot,et al.  Segregation and crosslinking in urea formaldehyde/epoxy resins: a study by high-resolution XPS , 2001 .