The Influence Study Of UiO-66/ammonium Polyphosphate On The Flame Resistance Of Polystyrene

Polystyrene(PS),as one of the five universal plastics in the world,has a very wide range of applications.This is mainly attributed to its excellent physical properties,such as low density,easy to process,heat-resisting,good wear resistance,good size stability and low cost and so on.At present,its main application fields include architecture,electronic equipment,automobile and aerospace,etc.However,PS is like a double-edged sword,which not only brings convenience and benefits to people,but also brings potential dangers to people's life.PS is a kind of organic macromolecule material which is easy to burn.Once PS start to burn,it will release a lot of toxic smoke,stimultaneously accompanied by melting dripping phenomenon.On the one hand,the toxic smoke will not only cause the trapped people and rescuers difficulties with breathing or even asphyxiation,but also increase the difficulty of rescue work.On the other hand,high temperature melt droplets can easily ignite the surrounding combustibles,thus increasing the combustion range and expanding the fire hazard.Therefore,in this trend,researchers have been committed to looking for high flame retardant efficiency,with ability to inhibit the release of smoke and environmental protection halogen-free flame retardants to improve the fire safety of polystyrene.Uio-66 is a kind of metal-organic framework materials(MOFs)containing flame retardant element zirconium(Zr),and its structure is formed by the octahedral framework containing Zr and 12 organic terephthalic acid ligands.Uio-66 has excellent thermal and chemical stabilities,and is one of the MOFs with best thermal stability.Generally speaking,some ligand defects will occur in the synthesis process of crystals,which will usually result in the porosity of UiO-66.Many studies have shown that the combination of MOFs and organic polymer materials can improve some properties of polymer materials.Ammonium polyphosphate microencapsulated by melamine resin(MFAPP)contains a large amount of nitrogen(N)and phosphorus(P)elements.MFAPP has low density,good stability,low toxicity and good dispersion.MFAPP decomposed When heated and on the one hand,it will release a large amount of non-combustible gases such as ammonia(NH3)and water vapor to dilute the surrounding air and combustible volatiles to delay combustion;on the other hand,polyphosphoric acid,monophosphoric acid and other products generated by APP's decomposition will act as a flame retardant in the condensed phase.In this paper,we studied the influence of introducing UiO-66 into PS matrix by melt blending on the fire safety performance of PS/UiO-66 composites.At the same time,the changes of the combustion performance and flame retardant performance of PS composites were further studied when UiO-66 and MFAPP synergistically acted on PS matrix.In this study,we used the X-ray diffraction(XRD),scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS)and transmission electron microscopy(TEM)to test and characterize the structure and morphology of APP,MFAPP,UiO-66 and PS composites and its residues.At the same time,we analyzed thermal properties and mechanical properties of PS composites,respectively by limiting oxygen index(LOi)test,thermogravimetric analysis(TGA)and electronic universal testing machine.Through cone calorimeter(CC)and micro calorimeter(MCC),we researched and analyzed the combustion performance of the PS composites.Finally,the graphitization degree of the residue were aslo analyzed by Raman spectrometer.The research results are as follows:(1)The introduction of UiO-66 can enhance the thermal stability of PS/UiO-66 and improve its flame retardant performance.To some extent,an appropriate amount of UiO-66 can also improve the mechanical properties of its composites.The results of cone calorimeter test showed that,comparing with the maximum heat release rate of pure PS(pHRR),PS/UiO-66-5wt%composites decreased to 540 kW/m2 from 744 kW/m2,decreased by 26.8%.The total heat release(THR)of PS/UiO-66-5 wt%composites was 58 MJ/m2,decreased by 14.7%compared with that of pure PS(68 MJ/m2).At the same time,the maximum smoke emission rate(pSPR)of PS/UiO-66-5wt%composites decreased from 0.77 m2/s(pure PS)to 0.42 m2/s,and the total smoke emission decreased from 63.6m2/m2(pure PS)to 41.1 m2/m2.Subsequently,thermogravimetric infrared analysis(TG-IR)was carried out on PS composites,and the results were basically consistent with the CC results mentioned above,indicating that the addition of UiO-66 has smoke suppression effect on the PS composites.(2)PS/MFAPP or PS/MFAPP/UiO-66 composites were prepared by by melting and blending.We studied the synergistic effects of MFAPP and UiO-66 on the PScomposites.XRD,SEM and other structural and morphological test results show that UiO-66 and MFAPP are evenly dispersed in PS matrix and compatible with the PS matrix.TG results showed that the introduction of MFAPP and UiO-66 can improve the thermal stability of PS composites to a certain extent.It can be concluded from the MCC results that the addition of UiO-66 and MFAPP can significantly reduce the heat release rate and the total heat release amount of PS composites.Among them,the pHRR value of PS/MFAPP/UiO-66-3wt%decreased to 564.3 W/g,decreased by 50.4%compared with that of 1137 W/g of pure PS,and the THR value also decreased to 32.1 kJ/g,reduced by 22.8%compared with that of 42.6 kJ/g.In addition,the test results of mechanical properties showed that appropriate amount of UiO-66 can improve the tensile strength of PS composites to a certain extent,while the elongation at break increases first and then decreases with the increase of addition amount.