Physicochemical properties and mechanical characters of methanol-modified melamine-formaldehyde (MMF) shell microPCMs containing paraffin

Microcapsules containing phase change materials (microPCMs) with melamine-formaldehyde (MF) shells have been applied in many thermo-regulation or thermo-saving fields. However, it is still essential to decrease the residual formaldehyde and enhance the mechanical properties of MF shells. The objective of this work was to fabricate a series of microPCMs containing paraffin by an in situ polymerization method using methanol-modified melamine-formaldehyde (MMF) prepolymer as shell material and investigate the physicochemical properties and mechanical characters of these microPCMs. FT-IR analysis indicates that the methanol-modified method can reduce the free formaldehyde in shell material through increasing the cross-linking structure. Optical microphotographs and SEM morphologies show that the microPCMs have regular globe shape with smooth surface. With the increasing of emulsion stirring rates from 1,000 to 5,000 rpm, the average diameters decreased sharply from 27 to 2.5 μm. The phase change temperature (T _m) of microPCMs samples with the core/shell ratios of 3/1, 2/1, 1/1, and 2/1 are 22.6, 23.0, 23.4, and 23.9 °C, which are nearly equaled to the T _m of pure paraffin (22.5 °C). Mechanical properties test data show that the MMF shells have larger yield point value than that of MF shell for microPCMs with the same core/shell ratio, which means that the methanol-modified method shell can greatly enhanced the resistance of deformation for MF shells. Moreover, MMF shells can resist the interface extrusion force in epoxy resin owing to their higher yield point of enhanced MMF shell.