PEI/PAA/APP三组分膨胀组装涂层阻燃改性苎麻织物

利用聚乙烯亚胺(PEI)的正电荷性及聚磷酸铵(APP)和聚丙烯酸(PAA)的负电荷性,通过层层组装技术在柔顺多孔的苎麻织物表面交替构筑了(PEI/PAA/PEI/APP)n膨胀型阻燃涂层,并对处理前后的苎麻织物的热稳定性和阻燃性等性质进行了表征.热失重分析(TGA)、微型量热仪(MCC)以及垂直燃烧测试(VFT)结果表明,阻燃处理后织物的热稳定性和阻燃性显著提高.同时与(PEI/APP)n试样相比,引入不同浓度的第3组分PAA在组装层数较少时通过增加PEI的电荷密度等作用可有效增加吸附量从而使上述性能有所提高,层数较高时由于APP和PAA的同性电荷紊乱,阻燃性的提升受到限制.

Flame Retardancy of Ramie Fabrics Treated by Layer-by-layer Assembly Technique of Tri-component PEI/PAA/APP

Multilayer flame-retardant coatings,consisting of opposite-charged polyelectrolyte polyethyleneimine (PEI),ammonium polyphosphate (APP) and polyacrylic acid (PAA),were constructed on the surface of soft and porous ramie fabrics by layer-by-layer (LBL) assembly technique.Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and field-emission scanning electron microscopy with an energy-dispersive X-ray (SEM-EDX) analysis confirmed that PAA was successfully introduced into the bi-component PEI/APP multilayer flame-retardant coatings.The P/C (phosphorus/carbon) ratio was clearly increased on the surface of the ramie fabric with the increase of the number of layers.The effect of PAA as a supplementary acid source on the flame retardancy of the treated ramie fabrics was studied by thermogravimetic analysis (TGA),microscale combustion calorimetry (MCC) and vertical flame testing (VFT).The results of the thermal properties showed that the char residue of the coated fabrics at high temperature during thermogravimetric analysis was significantly enhanced as compared with the untreated sample.Furthermore,the microscale combustion calorimetry revealed a reduction for both peak heat release rate (PHRR) and total heat release (THR).The surface morphologies of all the untreated and treated ramie fabrics after VFT demonstrated that the PEI/APP/PAA coated specimen preserved the integrity of the original texture of the ramie fabrics,and a dense and continuous expansion carbon layer was formed on the surface of the ramie fabric.The carbon layer effectively prevented oxygen and heat from penetrating into the substrate,thereby giving the ramie fabric excellent self-extinguishing properties.EDX spectra also revealed that the ratio of P/O (phosphorus/oxygen) and P/C of the char of the treated ramie fabric became high after combustion test.Compared to the bi-component (PEI/APP)n sample,the introduction of the third component PAA seemed to work at low assembly cycles by increasing the charge density of PEI,thus to improve the add-on of the FR coating on the fabric,but the concentration of PAA had little influence on the assembly process.However,the same charges may repel each other from the confusion of APP and PAA with high layers,causing the FR effect not that favorable.