Investigation Of Preparation And Performance Of Synergistic Flame Retardant Polyamide 6 Composites With Flame Retardant Chain Extenders

Polyamide 6(PA6)has been widely used in a variety of fields,including machinery manufacturing,telecommunications,electronic and electrical industries and so on due to its excellent mechanical strength and chemical resistance.However,PA6 materials is flammable.Moreover,the materials is easily hydrolysis degraded during melt processing due to its hetero-chain polymeric materials,which.Therefore,the PA6 material is endowed excellent flame retardant properties under maintaining its excellent mechanical properties,which is critical for preparing flame retardant PA6 materials with high comprehensive performance.In this these,three compounds containing epoxy groups were selected and used as flame retardant chain extenders because the epoxy groups can react with the terminal groups of PA6 including amino and carboxyl groups.The chain extenders mixed with aluminum diethylphosphinate(AlPi)respectively and incorporated into PA6 matrix,and the properties of materials were detailed investigated.The results indicated that 1.6 mm samples passes UL-94 V-0 rating during vertical burning tests when AlPi is used alone for flame retardant PA6 with the loading amount of 14 wt%.1,3,5-triglycidylisocyanurate(TGIC)containing triazine trione structure was used as chain extender and mixed with AlPi with a mass ratio of 3:97.The samples passed UL-94 V-0 flammability rating and the LOI value reached 30.5%when the total loading amount of flame retardant was only 11 wt%.This indicated that TGIC and AlPi presented an excellent synergistic flame retardant effect for PA6 material.With the addition of TGIC,the complex melt viscosity of materials was improved,the flammable gas was suppressed during combustion and the combustion intensity of materials was correspond reduced.Moreover,the residual char after combustion was also enhanced.Compared with PA6/AlPi composites,the mechanical properties of the PA6/AlPi/TGIC composites were improved due to the epoxy groups in the incorporated TGIC reacted with the terminal groups of PA6 matrix.In order to further improve the performance of the material,the hexa-[4-(glycidyloxycarbonyl)phenoxy]cyclotriphosphazene(CTP-EP)containing epoxy groups and phosphazene structure made in our laboratory was used as flame retardant chain extender.CTP-EP mixed with AlPi and used to flame retardant PA6.Compared with TGIC/AIPi flame retardant system,the CTP-EP/AlPi system presented the same flame retardant efficiency for PAS materials,but during the cone calorimeter test,the addition of CTP-EP made the ignition time(TTI)of the material significantly improved.Compared with TGIC,CTP-EP has a better cross-linking extension effect on PA6 materials,resulting in higher melt viscosity due to the six epoxy groups in the molecular structure.Thus the heat release rate,total heat release and other parameters was significantly reduced,and the surface of the char layer formed after combustion has become more compact.Compared with TGIC/AlPi system,the tensile,bending and impact strength of the material have been further improved due to the special structure of CTP-EP.Multiple flame retardant functional groups can play a synergistic flame retardant effect.In this work,9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)and 1,3,5-triglycidylisocyanurate(TGIC)were used to synthesis flame retardant chain extender DOPO-3,5-diglycidylisocyanurate(DOPO-TGIC)which have DOPO and triazine trione structure,and used in combination with aluminum diethylphosphinate for flame retardancy of PA6.The results indicated that 1.6 mm specimen successfully passed the UL-94 V-0 level and its LOI LOI was also enhanced.Compared to the use of TGIC as a flame-retardant chain extender,DOPO-TGIC/AlPi composites further increase the flame-retardant efficiency of the material due to the introduction of DOPO groups.