Water resistance, thermal stability, and flame retardation of polypropylene composites containing a novel ammonium polyphosphate microencapsulated by UV-curable epoxy acrylate resin

Abstract

In this work, ammonium polyphosphate (APP) was microencapsulated by UV-curable epoxy acrylate (EA) resin. The resulting novel EA-microencapsulated APP (EA-APP) was characterized by Fourier transform infrared spectra, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, granulometry, and thermogravimetric (TG) analysis. EA-APP was used to flame retard polypropylene (PP). The water solubility of EA-APP and the water resistance of PP/EA-APP systems were investigated. The thermal stability and combustion behaviors of PP/EA-APP composites were studied through TG and cone calorimeter (CC) tests, respectively. The water resistance test showed that the EA shell could significantly improve the water resistance of PP/APP. TG data illustrated that the char residue of EA-APP greatly increased by 149% compared with uncoated APP, and the thermal stability of PP/EA-APP composite was improved because of the microencapsulation of APP, with an increment of 248% for the char residue compared with PP/APP. CC test results indicated that the peak value of heat release rate, the total heat release, and the peak of smoke production rate of PP/EA-APP decreased in comparison with PP/APP. The mechanism for the improvement of flame retardancy in CC test was discussed based on the experimental results. EA resin containing a large number of hydroxyl groups might promote the dehydration reaction in EA-APP, which facilitated the formation of char residue and the stabilization of APP. Consequently, the flame-retardant efficiency for APP was improved because of the presence of EA shell. Copyright © 2014 John Wiley & Sons, Ltd.