The Surface Modification Of Intumescent Flame Retardants And Their Application In Polypropylene And Polylactic Acid

Polypropylene(PP)is used in many areas including automotive industries,electronic appliances and building due to its non-toxicity,easy processability and good mechanical properties,etc.Polylactic Acid(PLA)is a renewable and biodegradable material without any pollution from its synthesis to recycle.PLA has been applied in tableware,food packaging and medicine,etc.However,the inherent flammability of the two polymers leads their use accompanied with serious fire hazards.Therefore,the flame retardancy of PP and PLA has been a key factor for their wide use.Intumescent flame retardant(IFR)is commonly used in flame retardant modification of polymer in consideration of its low(no)toxicity,low smoke and other advantages.However,the relatively high loading and poor compatibility certainly damage the mechanical properties of flame retardant materials.Meanwhile,the majority of IFR is also easily exudative and moisture-sensitive.In this work,IFRs were surface modified with different methods,and then were incorporated with PP and PLA,respectively.The flame retardancy and other properties of two polymer composites were studied.The main content of this work is as follows.1.Pentaerythritol octahydrogen tetraphosphate(PEPA)was surface modified by silane coupling agent KH550 to prepare Si-PEPA,and then was introducted into PP with melamine polyphosphate(MPP).The results indicate that the LOI of PP/IFR composite is improved to 32.5%from 31.5%,and the pHRR and THR are respectively decreased to 166 kW/m2 and 66 MJ/m2 from 241 kW/m2 and 94 MJ/m2 due to the modification.The PP/IFR composite containing Si-PEPA can still reach UL-94 V-1 rating after soaking in water at 70? for 72 h.Besides,the tensile strength of PP/IFR composite containing Si-PEPA is improved to 33.1 MPa from the 30.0 MPa of PP/IFR composite containing PEPA.2.TPU-IFR flame retardant masterbatch was prepared with thermoplastic polyurethane(TPU)as carrier,maleic anhydride grafted polypropylene(MA-g-PP)as compatilizer and IFR,and the effects of TPU-IFR on flame retardancy and other properties of PP were studied.The results show that TPU-IFR masterbatch has an improved flame retardancy efficiency than IFR.When the content of IFR is 18 wt%,the UL-94 rating of PP/22.5TPU-80%IFR composite is improved to V-0 from V-1 of PP/18IFR,and the LOI is increased to 31.5%from 29.2%.The PP/22.5-80%IFR composite can still reach UL-94 V-1 rating after soaking in water at 70? for 168 h.Besides,the samples containing TPU-IFR masterbatch have improved mechanical properties.3.Ammonium Polyphosphate(APP)was respectively coated with polysiloxane(PSi)and polyborosiloxane(PBSi),preparing Si-APP and BSi-APP,and then was introduced into PLA.The results indicate that the two coated APP have better flame retardancy efficiency than APP.The PLA composite containing only 5 wt%BSi-APP can reach UL-94 V-0 rating,and the LOI is improved to 26.7%.PLA/7%Si-APP and even PLA/5%B Si-APP can keep the UL-94 V-0 rating after soaking in water at 25 ? for 168 h.Meanwhile,the PLA composites containing coated APP have better mechanical properties.