EG-based coatings for flame retardance of shape stabilized phase change materials

Abstract

Shape stabilized phase change material (SSPCM) is a promising thermal storage material used in energy-saving buildings, and much attention has been paid on its flame retardant property. In this paper, surface coating strategy was used to improve the flame retardance of SSPCMs (paraffin/polymer matrix/OMMT = 60/40/20). Three coatings, including acrylic resin/expandable graphite (EG), alkyd resin/EG and epoxy resin/EG, were surface coated on SSPCMs. Their flame retardant effects were evaluated by horizontal burning test, limiting oxygen index (LOI) determination, vertical burning test and cone calorimeter test. The results showed that all surface coated SSPCMs exhibited excellent flame retardance when the EG content exceeded a certain level. The horizontal burning times were increased largely; the UL-94 V0 level was achieved; and the LOI values were increased from 17.4 vol.% to over 30 vol.%. Moreover, the peak heat release rates (PHRRs) were decreased by 62–84%, and the heat release processes extended remarkably with reduced total smoke productions. The flame retardant mechanism of the surface coating strategy was investigated by in-situ Fourier transfer infrared spectrometry (FTIR) and thermogravimetric analysis (TGA). It was found that the coatings could hinder the escape of gaseous paraffin at low temperatures. Once exposed to fire or at high temperatures, the formed thick porous char layers helped to delay paraffin evaporation, trap generated combustibles and block the spread of oxygen and heat into the matrix.