Study On The Performance Of Phosphorus-containing Polyurethane Synergistic Ammonium Polyphosphate Flame-retardant EPDM

EPDM rubber has the characteristics of good electrical insulation,aging resistance,solvent resistance,and strong filling ability.However,EPDM is a non flame-retardant polymer material with low limiting oxygen index.It is easy to cause smoke suffocation death during fire disaster,so the study of low-smoke flame-retardant EPDM rubber has the theoretical and practical significance.Phosphorous polyurethane elastomers were synthesized and used as carbon sources to form intumescent flame retardant（IFR）with ammonium polyphosphate（APP）to obtain flame-retardant EPDM.Meanwhile two smoke suppression synergists（Ammonium octamolybdate or zinc hydroxystannate）were chose to compound with the IFR for researching the effect of flame retardant on the flame retardant and physical and mechanical properties of EPDM.The modification of ammonium polyphosphate（APP）to improve the water resistance of APP and the compatibility with the matrix material was carried out.Rotorless vulcanizer,vertical combustion,oxygen index,cone calorimetry,thermogravimetric infrared combined use,thermogravimetry,tensile machine and other characterization methods were used to analyze the vulcanization characteristics,flame retardancy,thermal degradation,physical and mechanical properties of flame-retardant EPDM etc.With MDI being used as the hard segment,PCL or PTMG as the soft segment,and BDO or N,N-bis（2-hydroxyethyl）aminomethylenephosphonic acid diethyl（FRC-6）as the chain extension,phosphorus-containing（or non-phosphorus-containing）polyester and polyether polyurethane were synthesized.The IFR and ¹H-NMR confirmed that polyurethane elastic materials had been successfully synthesized.Elemental analysis showed that phosphorus has been successfully introduced into the structure of phosphorus-containing polyurethane;Thermogravimetric data showed only one T_max peak in the phosphorus-containing polyurethane,indicating the better compatibility of soft and hard segments The highest carbon residue rate of phosphorus-containing polyurethane of 8.8%was obtained.The results of polyurethane/APP/EPDM showed that EPDM with phosphorus-containing polyurethane had the highest values of oxygen index and carbon residual rate.Compared with the addition of pentaerythritol/APP,the improved was obtained tensile strength,tear strength,elongation at break and abrasion resistance of polyurethane/APP flame-retardant EPDM.Among them,hosphorus-containing polyurethane/APP/EPDM has the best physical and mechanical properties.The results of Smoke suppression synergist/phosphorus-containing polyurethane/APP flame-retardant EPDM showed that ammonium octamolybdate or zinc hydroxystannate had a synergistic effect with IFR.The oxygen index of EPDM containing zinc hydroxystannate reached 28.5%and flame retardant is FV-0.Compared to EPDM with polyurethane/APP,EPDM with polyurethane/APP/zinc hydroxystannate had reduced heat release and smoke generation,higher carbon residue rate and carbon layer height,and improved tensile strength and tear strength.The main degradation products of EPDM were carbon dioxide and alkane gas.Ammonia gas is generated after APP is added.The addition of smoke suppression synergist and phosphorus-containing polyurethane has little effect on the degradation products of EPDM during combustion.The APP was modified with silane coupling agent,polyurethane and polyurea respectively.The modified APP has lower water solubility and higher hydrophobicity compared to APP.Modified APP/PER flame-retardant EPDM results showed that all modified APP can improve the flame retardant performance of EPDM.EPDM with polyurea modified APP had the best flame retardant performance,with vertical combustion being FV-0 level,oxygen index being 27.7%.After being soaked in hot water for 24 hours,it maintained high flame retardant performance with FV-0 level and 27.6%oxygen index.