Synergistic Flame Retardant LDPE With Microencapsulated Red Phosphorus And Aluminium Hypophosphite

Low-density polyethylene(LDPE) is lightweight, and has good electrical insulation properties, chemical resistance and good processing properties. However, LDPE is flammable and has poor heat resistance. It can easily cause a fire burning and produces LDPE melt drip when burned, which is easy to ignite other items and lead to the spread of fire, thus it is important to retardant LDPE. The traditional halogen flame retardant has certain environmental issues and security issues when burning; inorganic flame retardant will be some effect if only a lot of added, but will affect the mechanical properties of the material. Therefore, we have a research to improve flame retardant properties of the composites with halogen-free flame retardants. The main contents and results are as follows:1 Preparation of microencapsulated red phosphorus(MRP) and its application in the LDPE. MRP is prepared by in-situ polymerization, phenolic resins and melamine resins are the wall material. The stability and morphology of microencapsulated red phosphorus are characterized. Compared with the uncoated red phosphorus, moisture absorption, oxidation resistance, PH3 release and ignition points of MRP have been improved; thermal stability are enhanced. Besides, MRP can improve flame retardant properties of LDPE, when the loading of MRP is 10 phr, LOI index increased to 22.6 and the vertical burning pass V-2 rating levels. But TSR is increased.2 Aluminium hypophosphite application in the LDPE. AHP can significantly improve the flame retardant properties of LDPE and solve the melt drip phenomenon. When the loading of AHP is 50 phr, LOI index of the composites is 27.5, and the UL-94 reaches V-0 levels. AHP reduced maximum heat release rate and TSR of composite significantly, which improve the safety of the composite; AHP can promote the formation of a carbon layer, the strength of the char is gradually increased with the increase of the content of AHP.3 Microencapsulation red phosphorus and aluminum phosphate compound flame retardant LDPE. Aluminium hypophosphite and microencapsulated red phosphorus compound significantly improved the flame retardant properties of the composite materials, They have good synergy, this synergy reduce the loading of the flame retardant, HRR and TSR of the composites and extend the burning time of the composites. AHP can significantly promote the formation of char, phosphoric acid which generate from the degradation of MRP can mix with char to improve the barrier properties of the protective layer. the maximum weight loss temperature of LDPE / 40AHP-MRP composites is increased. In addition, the tensile strength, flexural strength and flexural modulus are increased, the elongation at break and the processing property are decreased, but after modified with EVA, elongation at break and processability are improved.