| Thermoplastic elastomer(TPE)composed of oil-filled styrene-ethylene/butylene-styrene block copolymer(O-SEBS)and polypropylene(PP)possesses excellent mechanical properties,electrical properties and chemistry stability.It has been widely used in wire and cable,medical equipment,automotive industry and other fields.However,TPE is flammable and its extensive application is limited.Currently,there are some key problems such as low flame retardant efficiency and poor water resistance in flame retardant TPE composites.Therefore,the investigation and development of flame retardant systems with high efficiency and excellent water resistance for TPE composites has important scientific significance and good practical application prospects.In this thesis,the O-SEBS was prepared by mixing SEBS with naphthenic oil at a mass fraction of 2:1,and the O-SEBS/PP composites(TPE)was prepared by blending O-SEBS with PP at a mass ratio of 2:1.Piperazine pyrophosphate(PPAP)combined with aluminum diethylphosphinate(AlPi)were incorporated into the O-SEBS/PP composites to preparing the flame retardant composites.The 1.6 mm samples passed UL-94 V-0 rating without dripping during vertical burning test and the limiting oxygen index(LOI)was 28.5%when the total loading amount of flame retardant was 25 wt%with the mass ratio of PPAP/AlPi was 4:1.Compared with the previously reported works,the presented PPAP/AlPi system exhibited high flame retardant efficiency for O-SEBS/PP composites.Compared with that of neat O-SEBS/PP composites,the heat release rate(HRR),total heat release(THR)and smoke release rate(SPR)of the flame retardant composites significantly reduced with the introduction of PPAP/AlPi.The Py-GC-MS tests indicated that PPAP/AlPi system exerted flame retardant effect in gas phase,which interrupted the combustion reaction and then declined the combustion strength of the samples.Moreover,the expanded,dense and integrated char layer was generated on flame retardant composites surface during combustion,which effectively inhibited the transmission of oxygen,heat and flammable gases between the combustion zone and the interior matrix underlying the char layer.PPAP/AlPi system exerted good synergistic flame retardant effect both in gas and condensed phase,and the O-SEBS/PP composites were endowed excellent flame retardant performance.PPAP presented good flame retardant effect for TPE materials,however,the water resistance performance of PPAP was required to be further improved.In order to solve the water resistance properties of flame retardant TPE composites,dimelamine pyrophosphate(DMPy)combined with AlPi were introduced into TPE materials.The results revealed that the 1.6 mm samples acheived UL-94 V-0 rating and the LOI was 27.2%when the total addition amount was 38 wt%with the mass ratio of DMPy/AlPi of 1:1.After the sheets were soaked in water at 70℃ for 168 h and dried to constant weight,they still passed UL-94 V-0 rating with the LOI value of 26.4%.It indicated that the prepared flame retardant TPE composites exhibited excellent water resistant performance.The measurement of X-ray photoelectron spectroscopy indicated that PPAP/AlPi migrated towards to the materials surface during water resistance test.The combusition parameters such as heat release rate(HRR)of the material after water resistance test were slightly lower than those of flame retardant TPE before water resistance test.The contents of flame retardant elements were slightly increased on the surface of residue char due to the water resistance tests.The mechanical properties of the samples were almost no declined after water resistance test.It could be concluded that the obtained flame retardant TPE composites by incorporating DMPy/AlPi system possessed superior water resistant performance. |
