Preparation And Properties Of Melamine-formaldehyde Microcapsules And MicroPCMs/epoxy Composites

In situ polymerization, a convenient and reaction-controllable technology, can be applied to synthesize microcapsules with adjustable particle size. Microcapsules containing phase change materials can solve a great many problems when phase change materials are handled and applied in many processes. Microencapsulated phase change materials (MicroPCMs) with advantages, such as apparent thermal stability, comparatively better mechanical strength, can be applied to foam composite materials, thermosmart fibers, energy-saving wall materials, solar heating systems and many other fields. In this study, paraffin and dodecanol was respectively encapsulated with melamine resin by in situ polymerization. The preparation conditions were improved. The dodecanol microPCMs/epoxy composites were prepared and effects of dodecanol microPCMs on the composites were researched.Fourier transform infrared spectra (FTIR) confirmed that the MR shell material was successfully fabricated onto the surface of the paraffin core. Scanning electronic microscopy (SEM) images suggested that the microcapsules exhibit a spherical and smooth morphology. The diameter of microcapsules was about 12-60μm. Furthermore, microcapsules had good morphologies starting polymerization at 50oC, pH≈4.4-4.9. Thermogravimetric analysis showed that these microcapsules were degraded in two distinct steps, and had good thermal stability below 180oC. The rupture of the microcapsules was mainly due to the volume expansion induced by the gasification of paraffin at high temperature. Microcapsules containing dodecanol were prepared with the conditions researched. FTIR confirmed that dodecanol core was successfully encapsulated into MF shell material. SEM images suggested that the microcapsules exhibited a depressive morphology. The diameter of microcapsules was about 1-16μm. Differential scanning calorimetry implied that the encapsulation efficiency and phase change temperature of microPCMs were affected by diameter and shell thickness of the microcapsules. The phase change temperature of dodecanol microcapsules was lower 1.5oC than dodecanol with the highest encapsulation efficiency (97.4%); These dodecanol microcapsules were synthesized at the stir rates of 4000rpm.The dodecanol micoPCMs were embeded in epoxy resin. Then the microPCMs/epoxy composites were treated by a thermal process with 10 times rapid temperature changes. The interface morphologies of microPCMs/epoxy composites were influenced by diameter and shell thickness of the microcapsules indicated by SEM images because of internal stress induced by different quantities of microcapsules in the composites. The microPCMs/epoxy composite containing dodecanol microPCMs, the core/shell (wt/wt) ratio was 1/1 and the average diameter was 16.20±7.82μm, showed comparatively better morphology.