Flame Retardation Of Polycarbonate With Modified Nanocarbon Black

Polycarbonate(PC)is a high-performance engineering plastic widely used in various industries,but its flammability and tendency to melt droplets pose great hazards,limiting its development in high-end applications.Therefore,it is of great significance to prepare highperformance flame-retardant PC.In this study,two modified nanocarbon black flame retardants were prepared by surface modification of nanocarbon black using siloxanes and sulfonates,and their effects on the comprehensive properties of PC(mainly flame retardant)were studied.Firstly,sulfonated nano carbon black(CB-g-SS)was prepared by grafting sulfonic acid salts onto the surface of nano carbon black using a thermal solvent method,and was added to PC by melt blending to obtain PC/CB-g-SS composite materials.The results showed that 3 wt%CB-g-SS could make PC reach UL-94 V-0 level in vertical combustion tests,and the oxygen index(LOI)of PC/CB-g-SS composite materials was improved compared to pure PC.The peak heat release rate(PHRR)and total smoke release(TSR)of PC/3CB-g-SS composite materials in cone calorimetry test were reduced by 48.1%and 24.8%compared to pure PC.It was found that CB-g-SS flame retardant mainly relied on the synergistic flame retardant effect of nano carbon black and sulfonic acid salts in the condensed phase,which could promote the formation of a dense char layer in the condensed phase,playing a good barrier effect.However,the total heat release(THR)of the composite material increased slightly in the cone calorimetry test,and the impact strength decreased with the increase of carbon black content.Secondly,based on the research of CB-g-SS flame retardant,POSS with a large number of active reaction groups was used as a bridge to graft onto the surface of nano carbon black,and then the active groups in the POSS molecule were sulfonated to obtain a sulfonated POSS-based nano carbon black flame retardant(CB-g-SSPOSS),which was added to PC by melt blending to obtain PC/CB-g-SSPOSS composite materials.The results showed that only 1 wt%CB-gSSPOSS could make PC reach V-0 level in vertical combustion tests,and the LOI of PC/lCB-gSSPOSS composite materials reached 31.3%.The PHRR and THR of PC/1CB-g-SSPOSS composite materials decreased by 39.0%and 8.7%respectively,and the TSR decreased by 20.9%.Through mechanism analysis,CB-g-SSPOSS relied on the synergistic flame retardant effect of nano carbon black,sulfonic acid salts and siloxanes in the condensed phase,showing extremely strong condensed-phase flame retardancy and smoke suppression ability.In addition,PC/CB-g-SSPOSS composite materials still maintained good mechanical properties while having good flame retardancy,with tensile strength equivalent to pure PC,and impact strength and elongation at break improved compared to PC/CB-g-SS,but slightly lower than pure PC.The transparency of PC/CB-g-SSPOSS composite films decreased,but the UV shielding ability was significantly improved.Thirdly,CB-g-SSPOSS was used as a synergistic flame retardant for HPTCP,and CB-gSSPOSS/HPTCP composite flame retardants were added to PC in a certain proportion.The results showed that PC composite materials with 0.5 wt%CB-g-SSPOSS and 3.5 wt%HPTCP could reach UL-94 V-0 level in vertical combustion tests,and the LOI was increased to 31.5%.Compared with pure PC,the PHRR,THR and TSR of PC/0.5CB-g-SSPOSS/3.5HPTCP composite materials decreased by 50.2%,27.0%and 26.2%respectively,showing excellent flame retardancy and smoke suppression.In addition,the mechanical properties of PC/CB-gSSPOSS/HPTCP composite materials could be maintained at a good level,and the composite films had a certain transparency and good UV shielding performance.