| Unsaturated polyester(UPR)has been widely applied in ships,construction,automotive,electronics and other areas due to its advantages of low cost,easy processing,excellent mechanical properties and corrosion resistance.However,the intrinsic flammability severely retrained their applications.Intumescent flame retardant(IFR)can effectively improve the flame retardancy of unsaturated polyester.However,most IFR systems are multi-component,and the components were difficult to be uniformly dispersed.The synergistic flame retardant effect of components in IFR was not satisfied.The mono-component IFR intergrated the components into one molecule,which lead to much better synergistic flame retardant effect between gredients.The mono-component IFR was expected to endow more excellent flame retardant properties for the unsaturated resin.In this thesis,melamine methylphosphonate(MMP)was synthesized from methylphosphonic acid and melamine.Its chemical structure was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy.The thermogravimetric analysis(TGA)tests indicated that the initial thermal decomposition temperature of MMP was 228? and the char residual was 41.2 wt%at 800?.The flame retardant exhibited excellent thermal stability and charring capability.When 21 wt%MMP was introduced,the UPR thermosets achieved UL-94 V-0 grade during vertical burning tests and the limiting oxygen index was as high as 38.5%.Compared with the previous reported works,MMP exhibited much higher flame retardant efficiency for UPR thermosets.The cone colorimeter(CONE)tests showed that the addition of MMP reduced the combustion parameters such as heat release rate(HRR),total heat release(THR)and smoke release of UPR thermosets,and the char residue at the end of combustion was enhanced.The continuous,expanded,impact and partially graphitized char layer was formed on the surface of the FR-UPR thermosets during the combustion.The char layer exhibited good strength and thermal stability,which effectively blocked the transfer of heat and mass between combustion zone and the interior of the char layer during combustion.As a result,the combustion intensity of the matrix was effectively inhibited.The pyrolysis-gas chromatography-mass spectrometry(PY-GC-MS)analysis of the flame retardant and materials indicated that the flame retardant generated phosphine radical.This compound effectively captured the free radical generated from UPR and then blocked the free radical chain reaction of the material during combustion.As a result,the unsaturated polyester materials was endowed excellent flame retardant performance due to the introduction of MMP.Meanwhile,the mono-component intumescent flame retardant defined as piperazine methylphosphonic acid neopentylglycol ester(PPMPNG)made in our lab was used to preparing the flame retardant UPR thermosets.When the loading amount of PPMPNG was 15 wt%,UPR thermosets achieved UL-94 V-0 grade with the LOI value of 32.1%.PPMPNG presented superior flame retardant efficiency for UPR materials.The Py-GC-MS tests indicated that the flame retardant decomposed and produced phosphine oxide radical containing compounds.Some derivatives containing phosphine oxides were detected during pyrolysis process.It revealed the combination of phosphine radical and the decomposition product of UPR.The CONE tests indicated that PPMPNG exerted excellent flame retardant effect both in gas and condensed phase,and then the combustion intensity of the material was effectively reduced.Compared with pure UPR,the parameters such as HRR and THR of the flame retardant material were effectively declined.The analysis of the char layer after combustion showed that a high-quality,partially graphitized char layer was generated on materials surface during the combustion.It effectively inhibited the degradation and combustion of the material underlying the char layer.Comsequently,the flame retardant performance of UPR thermosets was effectively enhanced. |
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