| Fiber-reinforced polypropylene composites are the material based on thermoplastic resin polypropylene(PP)and reinforced fibrous skeleton.It is gradually replacing engineering plastics and metals widely used in automobiles,machinery,electrical appliances,construction and other industries due to the advantages of low density,low price and recyclable use.However,polypropylene is extremely flammable with high burning rate,a large amount of heat and forming molten droplets during combustion,which make it difficult to apply to a flame-retardant environment,and the environment and personal safety are also jeopardized by burning.In this paper,a novel intumescent flame retardant system for fiber-reinforced polypropylene materials was constructed in order to get a reinforced and flame-retardant.The flame retardant performance,mechanical performance and related mechanisms were also investigated.1)An intumescent flame retardant polypropylene composite was prepared with a novel intumescent flame retardant system,which was built of combining aluminum diethyl hypophosphite(ADP)with ammonium polyphosphate(APP)and pentaerythritol(PER).The results showed that the combination of ADP and APP/PER can effectively improve the flame-retarded compared with traditional intumescent flame retardants.When the ratio of ADP and IFR(APP:PER=3:1)was 1:6,the total additionkept at 24wt%,the limiting oxygen index(LOI)of flame-retarded polypropylene reached to 29.8%,and the vertical combustion rating passed UL94 V-0.However,APP/PER/ADP has a poor flame-retardant effect on glass fiber reinforced polypropylenedue to the wick effect from glass fiber.Glass fiber treated with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide grafted vinyl silane coupling agent(DOPO-A172)and then combined with APP/PER/ADP was used to prepare flame retarded glass fiber reinforced polypropylene.The results showed that DOPO-A172 showed interfacial flame-retardant properties,which can increase the LOI of composites from 23.9% to 25.8%,but still can not achieve any flame retardant level.2)The laboratory-made phosphorus-nitrogen expanded flame retardant(MPN)was used to prepare flame-retardant glass fiber reinforced polypropylene composites.It was shown that MPN has a good flame retardant effect in polypropylene composites.When the addtion of flame retardant was 22wt%,the composite reached UL94 V-0 rating.When the amount was 24wt%,the LOI of compositewas as high as 37.9% meanwhile,the notched impact strength,tensile strength and bending strength of the composite were 8.3k J/m2,56.5MPa and 98.8MPa respectively.MPN made the composite an environment-friendly material with low smoke and low toxicity during combustion process.The surface-modified silica(Si O2-ME)was used as a flame retardant synergist to enhance the flame-retardant effect of glass fiber-reinforced polypropylene composites.The results showed that Si O2-ME has little effect on the flame-retardant properties of the composites,but could significantly improve the mechanical properties of flame-retardant fiber reinforced PP composites.When the addition amount of flame retardant and Si O2-ME were respectively 24wt% and 2wt%,the flame-retardant PP composite passed UL94 V-0,the LOI value reaches to 28.8%,meanwhile,the notched impact strength was 9.9 k J/m2,the tensile strength was 67.0 MPa,and the bending strength was 106.6 MPa.3)Flame-retardant sisal fiber reinforced polypropylene composites were prepared with APP/PER/ADP as flame retardant.The results showed that when the amount of flame retardant was 24wt%,the flame-retardant of PP/SF composite passed UL94 V-0 and the LOI reached 24.6%.Ni NO3 was used inthe flame-retardant PP/SF composite,due to its catalytic carbonization effect.It isshown that the addition of Ni NO3 could improve the residual carbon quality of PP/SF composites,which made its flame retardancy rating reached UL94 V-2,and the LOI raised to 26.1%. |
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