Preparation of melamine borate coated red phosphorus microcapsules and use of zinc borate as synergistic flame retardant in polyethylene

Abstract

Microcapsules (Mic-MBP) based on the melamine borate coated red phosphorus (RP) were prepared, and its synergistic flame retardant with zinc borate (ZB) on polyethylene (PE) was investigated. The flame retardant properties of the PE/20% Mic-MBP/10%ZB were superior to that of PE/20%RP/10%ZB. Furthermore, the limiting oxygen index of PE/20%Mic-MBP/10%ZB was 25.2%, and PE/20%Mic-MBP/10%ZB reached the UL-94V-0 rating. Compared with PE, the peak heat release rate (pk-HRR), total heat release (THR) and average effective heat of combustion (av-EHC) of PE/20%Mic-MBP/10%ZB had decreased. In addition, the flame retardant mechanism was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) and Fourier transform infrared spectroscopy (FT-IR). The results showed that the residual char of PE/20%Mic-MBP/10%ZB had thermal stability, and the formation of phosphorus free radicals and nonflammable gases effectively reduced the burning intensity of the gas phase. It indicated that Mic-MBP/ZB showed a condensed and gas phase flame retardant effect.

Preparation and Characterization of Cyclodextrin Coated Red Phosphorus Double−Shell Microcapsules and Its Application in Flame Retardant Polyamide6

“…The RP acted as acid source, and the shell materials acted as gas and carbon sources. During combustion, Mic−DP first decomposed to nonflammable inert gases, including NH 3 and H 2 O [ 23 ], resulting in the reduction of concentration of flammable volatiles. Then, RP formed phosphorous acid and phosphorous free radicals, which reacted with crossed β−CD to promote the formation of carbon layer and trapped the active free radicals in the gas phase, respectively.…”

“…Pyridine and acetone were purchased from Guangzhou Chemical Reagent Factory, Guangzhou, China. Microcapsules based on melamine borate coated red phosphorus (Mic−MBP) were prepared by our laboratory [ 23 ].…”

Enhanced flame retardancy, smoke suppression, and acid resistance of polypropylene/magnesium hydroxide composite by expandable graphite and microencapsulated red phosphorus

“…This is not unexpected as MRP and other phosphorus-containing FRs are known to be able to generate POÁ free radicals in case of oxidation, which captures HÁ and ÁOH free radicals and terminates chain reaction in flame. [5,[34][35][36][37] Insufficient combustion in the gas phase leads to increase of smoke release.…”

Investigation of the synergistic effect of red phosphorus and magnesium hydroxide on the thermal degradation behavior and flame resistance of the intumescent fire‐retardant polypropylene system

“…30,31 However, RP has some drawbacks such as strong moisture absorption and chemical instability, leading to the requirement to combine it with other flame retardants. It has been found that RP exhibits a flame-retardant synergistic effect with novolac and melamine, 32 aluminum isobutylphosphinate, 33 melamine borate and zinc borate, 34 and titanium dioxide. 35 In this work, RP and MH were introduced into PP/EG composites to enhance the compactness of the char structure due to the covering and adhesive efficiency of high-viscosity compounds generated by the thermal decomposition and interaction of these materials.…”