包覆型MCA/PA 6复合材料的制备及其阻燃性研究

以水为反应介质、无水乙醇为溶剂,将正硅酸四乙酯(TEOS)制备成二氧化硅(SiO_2)溶胶,利用溶胶的网络结构对三聚氰胺氰尿酸盐(MCA)进行表面包覆,制备出包覆型MCA阻燃剂;通过熔融共混方式,将包覆前后MCA与聚己内酰胺(PA 6)切片混合制备成不同阻燃剂含量的阻燃PA 6复合材料;采用红外光谱仪X射线光电子能谱仪、差示扫描量热仪、热重分析仪、垂直燃烧法和极限氧指数法等研究了阻燃PA 6复合材料的结构、热性能及阻燃性能。结果表明:SiO_2溶胶成功接枝在MCA表面,且主要分子结构没有发生改变;随着阻燃剂含量的增加,PA 6复合材料的熔点均有降低,但下降幅度较小;包覆型MCA在材料燃烧过程中能够有效参与成炭,在材料表面形成致密的保护层,增强PA 6复合材料的凝聚相阻燃效果,提高其阻燃性能;随着阻燃剂含量增加,PA 6复合材料的阻燃性逐步提高,添加包覆型MCA质量分数为8%时,PA 6复合材料阻燃性可达到UL-94 V-0等级,极限氧指数为28%。

Preparation of coated MCA/PA 6 composites and its flame retardancy

Tetraethyl orthosilicate(TEOS)was prepared into silicon dioxide(SiO 2)sol by using water as reaction medium and absolute ethanol as solvent.The surface of melamine cyanurate(MCA)was coated with sol network structure to prepare coated MCA flame retardant.The flame retardant PA 6 composites with different flame retardant content were prepared by melt blending polycaprolactam(PA 6)chip with coated and uncoated MCA.The structure,thermal properties and flame retardant properties of flame retardant PA 6 composites were studied by infrared spectrometry,X-ray photoelectron energy spectrometry,differential scanning calorimetry,thermogravimetric analysis,vertical combustion method and limiting oxygen index test.The results showed that SiO 2 sol was successfully grafted on the surface of MCA,and the primary molecular structure did not change;the melting point of PA 6 composite decreased at a slight amplitude with the increase of flame retardant content;however,the coated MCA can effectively participate in char formation during the material combustion process and form a dense protective layer on the surface of the material,which enhanced the condensed phase flame retardant effect of PA 6 composite material and improved its flame retardancy;the flame retardancy of PA 6 composite increased gradually with the increase of flame retardant content;and the flame retardancy and the limiting oxygen index of PA 6 composite can reach UL-94 V-0 level and 28%,respectively,when the mass fraction of coated MCA was 8%.