Preparation and mechanism of fly ash based composite fillers with different morphologies and its application in filling polyamide 6

In order to realize the high value-added utilization of coal-based solid waste fly ash (FA) and enhance the performance of polyamide 6 (PA6), three kinds of core-shell structure FA-based composite fillers with different shell morphologies (nano-flake, spherical and rod-like particles) were prepared using FA as raw material, MgSO4, MgCl2, Mg(NO3)2 and NaOH as coating agents, which were noted as composite powder 1 (CP1), composite powder 2 (CP2) and composite powder 3 (CP3). The specific surface areas were enhanced to 97.41, 58.59 and 20.21 m2 g-1 from 1.71 m2 g-1 (FA), while the corresponding pore volumes were increased from 0 to 0.31, 0.22 and 0.06 cm3 g-1. Si-O-C-O-Mg and Si-O-Mg-OH bonds were formed between Si-O-Si, Si-O bonds on the surface of FA and hydrated MgCO3 (MCH), Mg(OH)2 (MH). Three types of CPs were filled into PA6, respectively. After filling, CP2 caused silver grain effect when the material was damaged, which had better toughening effect on the matrix. Compared with pure PA6, the limiting oxygen index of pure MH, FA, CP1, CP2, and CP3 increased by 0.60, 0.70, 1.30, 2.30 and 4.10%, respectively. The thermal deformation temperature was increased by 29.10, 46.20, 53.70, 31.90 and 42.00 degrees C respectively. The melting index decreased by 1.05, 0.70, 0.49, 0.17 and 0.47 g/min, respectively.