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Synthesis and Characterization of Melamine‐Urea‐Formaldehyde Microcapsules Containing ENB‐Based Self‐Healing Agents
Author(s) -
Liu Xing,
Sheng Xia,
Lee Jong Keun,
Kessler Michael R.
Publication year - 2009
Publication title -
macromolecular materials and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 96
eISSN - 1439-2054
pISSN - 1438-7492
DOI - 10.1002/mame.200900015
Subject(s) - materials science , thermogravimetric analysis , urea formaldehyde , melamine , composite material , melamine resin , particle size , scanning electron microscope , self healing , polyurethane , in situ polymerization , polymerization , polymer , chemical engineering , nuclear chemistry , polymer chemistry , adhesive , chemistry , coating , medicine , alternative medicine , layer (electronics) , pathology , engineering
Abstract Microcapsules for self‐healing applications were produced with a melamine‐urea‐formaldehyde (MUF) polymer shell containing two different healing agent candidates, 5‐ethylidene‐2‐norbornene (ENB) and ENB with 10 wt.‐% of a norbornene‐based crosslinking agent (CL), by in situ polymerization in an oil‐in‐water emulsion. Relatively neat outer surfaces with minor roughness were observed on the MUF microcapsules under optical and scanning electron microscopy. Shell thickness of the capsules ranged from 700 to 900 nm. Particle size analysis of the microcapsules showed narrow size distributions with a mean diameter of 113 µm for ENB‐filled and 122 µm for ENB + CL‐filled microcapsules at an agitation rate of 500 rpm. The microcapsules were found to be thermally stable up to 300 °C and exhibited a 10 to 15% weight loss when isothermally held at 150 °C for 2 h from thermogravimetric analysis. Overall, these MUF microcapsules exhibited superior properties compared to the urea‐formaldehyde (UF) microcapsules used extensively for self‐healing composites to date. In addition, the manufacturing process of MUF microcapsules is much simpler than those made from UF. Additional advantages of MUF microcapsules for self‐healing composites are discussed.