氨基碳纳米管/DOPO衍生物的协效阻燃及其对尼龙6性能的影响

Synergistic Flame Retardancy of Amine-based Multi-walled Carbon Nanotubes/DOPO Derivatives and Its Effect on the Properties of Nylon 6

将DOPO衍生物(DIDOPO)和氨基碳纳米管(MWCNTs)以一定的比例进行复配,添加到尼龙6(PA6)中熔融共混制得复合材料.运用万能试验机、热重分析仪、示差扫描量热仪、锥形量热仪及扫描电镜测试了各样本的力学性能、热稳定性、结晶性以及燃烧性能,并观察了炭层形貌.测试结果表明,加入MWCNTs后,复合材料的拉伸强度显著增强,与PA6/DIDOPO复合材料相比,其拉伸强度平均提升了55%.从非等温结晶曲线可以看出,加入MWCNTs后PA6复合材料的结晶初始温度(Tonset)和结晶峰温(Tc)都有明显提高,但由于MWCNTs的异相成核作用,结晶度降低.此外,锥形量热测试表明,当MWCNTs的添加量为2 wt%时,其热释放速率峰值(PHRR)为367.28 kW/m2,较纯PA6降低了58.9%.扫描电镜和拉曼测试分析表明MWCNTs的加入促进了致密结构炭层的形成,与DIDOPO有协效阻燃的作用.

A novel DOPO derivative(DIDOPO)is incorporated together with amine-based multi-walled carbon nanotubes(MWCNTs)into PA6 by melt blending.Mechanical properties,thermal stability,crystallinity,and combustion properties are measured using universal testing machine,thermogravimetric analyzer,differential scanning calorimeter,and cone calorimeter,respectively.After combustion,the morphology of char layer is further observed by a scanning electron microscope.The results show that MWCNTs-incorporated flame-retardant nanocomposites exhibit a tensile strength that is 55%higher than that of the PA6/DIDOPO composites.From the TG and DTG curves,it can be seen that the T5 wt%of PA6 composites increased slightly and the maximum weight loss rate temperature(Tmax)gradually improved after adding MWCNTs,indicating that the addition of MWCNTs delays the process of thermal degradation of the PA6 composites.With the incorporation of MWCNTs,the amount of residual carbon is also increased.From the non-isothermal crystallization curve,it can be seen that the crystallization initial temperature(Tonset)and crystallization peak temperature(Tc)of the PA6 composites are significantly improved with the addition of MWCNTs.However,the crystallinity is lower due to the heterogeneous nucleation of the MWCNTs.From UL-94 datas,the combustion time(t1+t2)is increased with the incorporation of MWCNTs into PA6/DIDOPO composites,which results in a V-1 level in the UL-94 test and a slightly increased LOI value.This phenomenon can be attributed to an increment in melt viscosity and a decrement in flow properties.Combined with the curves of effective combustion heat,total smoke release and CO release rate,it can be concluded that the synergistic effect between MWCNTs and DIDOPO weakens the thermal degradation process of the PA6 composites,thus increasing the incomplete combustion and reducing the complete combustion of the PA6 composites,which is beneficial to the flame retardance of the materials.Addition of 2 wt%MWCNTs results in a peak heat release rate(PHRR)of 367.28 kW/m^2,which corresponds to a 58.9%lower rate than that of pure PA6,as revealed by cone calorimetry.Based on SEM and Raman,a continuous and compact char layer is observed upon addition of MWCNTs,which is ascribed to a synergistic effect between MWCNTs and DIDOPO.