Synthesis Of Layered Rare Earth Metal Phosphonates And Their Flame-retardant Effect On Carbon Fiber Reinforced PC/ABS Alloys

Carbon fiber?CF?reinforced polycarbonate/acrylonitrile-butadiene-styrene copolymer?PC/ABS?alloy is widely used in the automotive industry,electronic appliances,mechanical instrumentation and communication equipment due to its good mechanical properties and heat resistance.However,when PC/ABS/CF composite was ignited,the polymer matrix was hard to carbonize,and the gap between CF and matrix provided a diversion channel for the molten drop.It would accelerate the polymer degradation during combustion,which caused“candle wick ignition”effect.It deteriorated the flame retardant properties of the composite and severely limited the application of the composite in the field of high flame retardant requirements.In order to address this problem,two kinds of lamellar phenylphosphonate rare earth metal salts were synthesized,and then combined with polyarylphosphate?PX-220?to flame-retard PC/ABS.The flame-retardant system could accelerate the char-forming rate of the polymer matrix and reduce the molten drop.It could rapidly catalyze carbonization of the polymer chain on the surface of the polyurethane/epoxy resin coated carbon fiber?EPCF?,and EPCF was utilized as the support framework of the char layer,thus effectively overcame the“candle wick ignition”effect,and the PC/ABS/EPCF composites with excellent mechanical properties and flame retardant properties were prepared.The synergistic flame-retardant mechanism of lamellar phenylphosphonate rare earth metal salts and carbon fiber were also studied.The main contents and results are as follow:Firstly,Polyarylphosphonate?PX-220?and hexaphenoxytriphosphazene?HPCTP?were combined to flame-retard carbon fiber reinforced PC/ABS alloy.The effect of EPCF,HPCTP and PX-220 on the mechanical properties and flame retardancy of PC/ABS was studied.It was found that when the amount of HPCTP/PX-220 was 15wt%and the mass ratio of HPCTP to PX-220 was 3:7,the limiting oxygen index?LOI?of PC/ABS was increased from 20.0%to34.0%,and it passed the UL-94 V-0 rating.Meanwhile,the peak heat release rate?PHRR?,average heat release rate?AV-HRR?and total heat release?THR?of the composite decreased by 61.3%,43.4%and 20.7%,respectively.Moreover,the maximum decomposion rate of the composite was reduced by 34%.The results of scanning electron microscope and energydispersive X-ray spectroscopy?SEM-EDX?,thermogravimetry-Fourier transform infrared spectrometry?TG-FTIR?and laser Raman spectroscopy?LRS?showed that HPCTP and PX-220 could promote the Fries rearrangement and cross-linking of PC,which quickly formed a dense char layer on the EPCF surface.HPCTP decomposed and released non-combustible gases such as NH₃,which diluted the combustible gases and oxygen around the polymer matrix.High efficient flame retardancy was realized through the synergism of the gas phase and condensed phase flame-retardant mechanism.Secondly,lanthanum phenylphosphonate?LaPP?was synthesized with lanthanum chloride and phenylphosphonic acid via reflux method,and characterized by SEM,X-ray diffraction?XRD?and Fourier transform infrared spectrometry?FTIR?.Subsequently,LaPP and PX-220 were combined to flame-retard PC/ABS/EPCF.The effect of LaPP and PX-220on the flame retardancy and thermostability of the PC/ABS/EPCF was investigated.The results showed that when the amount of LaPP/PX-220 was 8wt%and the mass ratio of LaPP to PX-220 was 2:3,the LOI value of PC/ABS/EPCF was increased from 20.0%to 30.6%,and it passed the UL-94 V-0 rating.Meanwhile,PHRR,AV-HRR,and THR of the composite decreased by 59.9%,33.5%,and 23.1%,respectively.The results of SEM-EDX,TG-FTIR,LRS and X-ray photoelectron spectroscopy?XPS?revealed that LaPP and PX-220 could promote the Fries rearrangement reaction of PC,inhibit the production of phenols and prevent PC from degradation and catalyze polymer carbonization on the EPCF surface.LaPP and EPCF could also be used as the skeleton to further improve the strength and compactness of the char layer.Meanwhile,LaPP could capture peroxy radicals during combustion,and inhibit the degradation of the polymer,thus further improved the flame-retardant efficiency.Finally,cerium phenylphosphonate?CePP?and zirconium phenylphosphonate?ZrPP?were synthesized with cerous nitrate,zirconyl oxychloride and phenylphosphonic acid through reflux method.The effect of the combination of the three metal salt phenylphosphonates?LaPP,CePP and ZrPP?and PX-220 on the flame retardancy and thermostability of the PC/ABS/EPCF were studied.The results showed that the lamellar metal phosphonates have a good synergism with PX-220 for flame-retarding PC/ABS/EPCF.When the amount of flame retardant was 8wt%and the mass ratio of metal salt phenylphosphonate to PX-220 was 2:3,LaPP,CePP and ZrPP could increase the LOI values of PC/ABS to 30.6%,30.4%and 30.2%,and they reached V-0,V-0 and V-1,respectively.Meanwhile,their PHRR,AV-HRR and THR were significantly decreased.The results of SEM-EDX,TG-FTIR,LRS and XPS revealed that LaPP,CePP and ZrPP could effectively improve the flame retardancy of PC/ABS by layer barrier and free-radical trapping effect.They could quickly catalyze polymer carbonization on the EPCF surface.Moreover,the size of LaPP and CePP is relatively larger,resulting better barrier effect and better flame retardancy.