High compact melamine-formaldehyde microPCMs containing n-octadecane fabricated by a two-step coacervation method |
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Authors: | Jun-Feng Su Zhen Huang Li Ren |
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Institution: | (1) Institute of Chemistry and Materials, Tianjin University of Commerce, Tianjin, 300134, People’s Republic of China;(2) Polymer Research Institute, College of Chemical Engineering and Technology, Hebei University of Technology, Tianjin, 300130, People’s Republic of China |
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Abstract: | Microcapsules containing n-octadecane were successfully fabricated by an in-situ polymerization process with melamine-formaldehyde (MF) prepolymer and
a hydrolyzed copolymer of styrene and maleic anhydride (SMA) as shell materials. To achieve a long service time of microcapsules
containing phase change materials (microPCMs), the compactness of shells was improved by adding the MF prepolymer twice. The
mechanism of this method was a two-step coacervation (TSC) under the help of hydrolyzed SMA compared to a one-step coacervation
(OSC). To understand the influence of both coacervations, properties of shells were investigated in terms of morphologies,
density, thickness, and stability by means of scanning electron microscopy (SEM), transmission electron microscopy, and thermal
gravimetric analysis (TGA). The data of shells thickness were achieved from the cross-section SEM images. It shows that the
average thickness of shells from two kinds of process are 0.1 μm. The density and stability in water of shells fabricated
by TSC are both higher than that of shells by OSC. TGA curves show the expected microPCMs of TSC losing weight from 200 to
400 °C. The release curves, relationship between time and logarithmic residual weight of core, show there are two decrease-linear
steps after curve regression. It can be concluded from all these results that the TSC method may be a promising method leading
to a compact shell structure for various application. |
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Keywords: | Microcapsules MicroPCMs Coacervation Compact Melamine-formaldehyde resin |
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