Development of one-step synthesized LDH reinforced multifunctional poly(amide-imide) matrix containing xanthene rings: study on thermal stability and flame retardancy

New exfoliated poly(amide-imide)/Zn-Al layered double hydroxide (LDH) nanocomposites were synthesized by solution intercalation using synthesized organo-modified LDH (OLDH) as nanofiller obtained by one-step method. The designed poly(amide-imide) (PAI) containing bulky xanthene rings in the side chains, aliphatic chains in the main chains and amide groups in the side and main chains was synthesized via direct polycondensation reaction with desired molecular weight. Poly(amide-imide)/LDH nanocomposites (PAINs) were prepared by different contents of OLDH and morphology, mechanical, thermal and flame retardancy of PAINs were studied. The dispersion of OLDH was quantified by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and the results showed a good dispersion for OLDH in the PAI matrix. According to the results of mechanical tests, the tensile strength of PAIN containing 5 mass% of OLDH increased to 70.1 MPa from 57.3 MPa of neat PAI without OLDH addition. The thermogravimetric analysis (TGA) results showed that the addition of OLDH resulted in a substantial increase in the thermal stability of the PAINs. The temperature at 5% weight loss (T-5) was increased from 281 degrees C to 323 degrees C for PAIN containing 5 mass% of OLDH as compared to neat PAI, as well the char yield enhanced greatly. Significant improvements in flame retardancy performance were observed for the nanocomposites from microscale combustion calorimeter (MCC) (reducing both the heat release rate and the total heat released).