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The synergistic effect between a char forming agent (CFA) and microencapsulated ammonium polyphosphate (MAPP) on the thermal and flame retardancy of polypropylene (PP) are investigated by limiting oxygen index (LOI), UL‐94 test, cone calorimetry, thermogravimetric analysis (TGA), scanning electron micrograph (SEM), and water resistance test. The results of cone calorimetry show that heat release rate peak (PHRR), total heat release (THR), and the mass loss of PP with 30 wt% intumescent flame retardant (IFR, CFA/MAPP = 1:2) decreases remarkably compared with that of pure PP. The HRR, THR, and mass loss decrease, respectively from 1140 to 100 kW/m2, from 96 to 16.8 MJ/m2, and from 100 to 40%. The PP composite with CFA/MAPP = 1:2 has the best water resistance, and it can still obtain a UL‐94 V‐0 rating after 168 hr soaking in water. Copyright © 2008 John Wiley & Sons, Ltd.

A novel intumescent flame retardant (IFR) poly(butylene succinate) (PBS) with an antidripping property using fumed silica as a synergistic agent was prepared. Ammonium polyphosphate, melamine, and fumed silica were added in PBS via melt blending. It was revealed that the flame retardant PBS exhibited both excellent flame retardance and antidripping properties when the three components of IFR coexisted at an appropriate proportion. The lowest total loading of flame retardant could be reduced to 17 wt % with the synergism of fumed silica, for the goal of vertical flammability (UL-94) V-0 rate. Scanning electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the morphology and composition of residual char, respectively. The combustion properties and thermal degradation behavior of the IFR-PBS composites were fully evaluated, and the possible flame retardant mechanism was proposed.

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Starch containing polypropylene (SCP) semibiocomposites were prepared by melted blend method. Microencapsulated ammonium polyphosphate (MCAPP) was added to the SCP not only to improve its flame retardant properties but also to restrain the reaction between ammonium polyphosphate (APP) and starch during processing. The flame retardant properties of SCP have been investigated by limited oxygen index (LOI), UL-94 test, and cone calorimeter test. The results of cone calorimeter show that the peak of heat release rate and total heat release of SCP decreases substantially compared with that of pure PP. The thermal degradation and gas products of PP/starch/MCAPP systems were monitored by thermogravimetric analysis (TGA) and thermogravimetric analysis−infrared spectrometry (TG-IR). Scanning electron micrograph (SEM) and X-ray photoelectron spectroscopy (XPS) measurements were utilized to investigate the chemical structure, as well as the surface morphology of the residual char.