Microencapsulation of styrene with melamine-formaldehyde resin

Melamine-formaldehyde (MF) resin-walled microcapsules containing styrene were prepared by in situ polymerization in an oil-in-water emulsion. In response to the characteristics of styrene (i.e., high volatility, non-polarity, low molecular weight, and low viscosity), the synthesis method was improved by optimizing the reaction conditions accordingly. It was found that utilization of macromolecular emulsifier of lower molecular weight, moderate dispersion rate, and higher feeding weight ratio of core/shell monomers is critical for the fast formation of capsules’ wall. The highest loading of styrene in the resultant microcapsules can be about 60%, and mean diameter of the capsules fell in the range of 20∼71 μm, which can be adjusted by changing processing parameters. It is believed that the present work provides a feasible approach to encapsulate monomers for manufacturing polyester based self-healing composites.