Synthesis Of A Novel N-alkoxyamine Containing Flame Retardant And Its Application In Polypropylene Film

Polypropylene(PP)film has been widely used in capacitor,electrical packaging,circuit board printing and sealed packaging due to its excellent electrical insulation,high transparency and sealing performance.However,PP matrix is flammable and its limiting oxygen index(LOI)value is only 17.0%.Polypropylene film is very flammable with serious droplets during combustion caused by its thin thickness and large specific surface ratio.Polypropylene film can reached required flame retardant rating with a large loading amount of traditional flame retardant used in PP sheets,which will severely deteriorate its mechanical,transparency and insulation properties.Therefore,it is of great significance to develop the flame retardant with high efficiency for polypropylene film.Hindered amines presented excellent photostabilization.Moreover,these compounds could decompose to generate nitroxide radical during heating or combustion.The produced nitroxide radical can quench the free radicals in the gas phase,and possessed high flame retardant efficiency.In this thesis,a novel flame retardant containing N-alkoxyamine groups 2,4,6-tri-(1-cyclohexyloxy-4-imino-2,2,6,6-tetramethylpiperidine)-1,3,5-triazine(T-TEMPOC)was designed and synthesized from cyanuric chloride,4-amio-2,2,6,6-tetramentylniperidine and cyclohexane.The chemical structures of the obtained compound and intermediates were well characterized and confirmed by Fourier transform infrared(FTIR),nuclear magnetic resonance(1H-NMR),electron paramagnetic resonance(EPR),mass spectra(MS).The results of thermogravimetric analysis(TGA)tests indicated that the initial thermal decomposition temperature of T-TEMPOC was 219 ℃.T-TEMPOC presented good thermal stability and satisfied the processing requirements of PP film.The composition of pyrolysis products of T-TEMPOC was investigated by pyrolysis gas chromatography mass spectra(Py-GC/MS)tests,and the results demonstrated that T-TEMPOC could decompose and generate different kinds of nitroxide radicals.The synthetic T-TEMPOC was incorporated into PP and prepared flame retardant PP film(NOR-PP film).The flame retardancy of films was investigated by vertical burning(UL-94),limiting oxygen index(LOI)and micro combustion calorimeter(MCC)tests.The results revealed the NOR-PP film with the thickness of 0.2 mm successfully passed UL-94 VTM-0 rating and its LOI value reached 27.3%when the loading amount of T-TEMPOC was only 2.0 wt%.The NOR-PP film was self-extinguished within 3-6 s after the films deviated from fire and there was no dripping during tests.This indicated the synthesized flame retardant possessed superior flame retardant efficiency for PP film.The mechanical properties tests revealed the introduction of T-TEMPOC slightly decreased the mechanical performance of the materials.The microscale combustion calorimeter tests demonstrated that the incorporation of T-TEMPOC into PP film obviously decreased the heat release rate(HRR)and total heat release(THR).From the TGA data,It could infer the introduction of T-TEMPOC inhibited the initial thermal degradation of PP on heating and thus enhanced the thermal stability of PP film.The composition of pyrolysis products of NOR-PP film during heating was measured by Py-GC/MS,and the mechanism of flame retardant on PP film could be deduced.T-TEMPOC could be decomposed and produced nitroxide radical on heating.In the initial stage on heating,nitroxide radicals could quench the alkyl radicals generated from thermal degradation of polypropylene,which could inhibit the degradation PP macromoleculars induced by radical and then improved the thermal stability of materials.During combustion,the nitroxide radicals could quench the radical chain reaction of combustion by capturing free radicals,thus inhibited the combustion of materials.Moreover,nitroxide radical was regenerated under the existing of peroxide generated from combustion.The cyclic process of nitroxide radical quenching free radicals and self-regeneration was constructed.