Study of enhanced heat transfer on controllable preparation of melamine resin microcapsules: Stirring, dropping, spraying and microchannel curing process

Microcapsules are widely used for their ability to encapsulate, deliver, and release active substances. Although non-ionic melamine resin microcapsules offer excellent adaptability and commercial potential, their preparation is often hindered by poor controllability. This study adopted a strategy combining process dissection and intensification, focusing on curing process. The stirring, dropping/spraying, and microchannel curing were systematically evaluated using infrared spectroscopy, particle size analysis, and computational fluid dynamics (CFD) simulations. Results showed that elevated temperatures disrupted the dynamic equilibrium among melamine-formaldehyde prepolymers, leading to an unstable curing phase. Enhanced heat transfer effectively shortens this period, mitigating issues such as broad particle size distribution, caking, and agglomeration. Among the evaluated methods, microchannel curing delivered the best performance, with significantly improved particle uniformity (D₅₀: 3.050 μm; Span: 3.36) compared to stirring curing (D₅₀: 32.329 μm; Span: 7.64). Caking and agglomeration were nearly eliminated, with the caking rate reduced to 1.58 mg/mL.