Thermo gravimetric analysis (TGA) of PA6/G and PA6/GNP composites using two processing streams

The thermogravimetric (TGA) responses of PA6 composites filled with synthetic Graphite (G) and Graphite nanoplatelets (GNP) each on 5 cumulative loading levels were investigated using two processing streams each of a common processing strain. To determine the effect of the 2 carbon fillers on the thermal stability of unfilled PA6, the temperatures at which 5, 20 and 50 wt% losses occurred were observed for the composites and the unfilled PA6. Weight lost at 460 °C and the carbon char at 600 °C were also noted. Effects of varying extrusion screw speeds as well as sonication amplitudes with time were given cognisance. To evaluate the effect of processing on the thermal response of the composites, two in situ polymerised streams and 2 melt extrusion streams with each set being equivalent in ‘magnitude of strain histories’ were characterised using TGA. The TGA for the unfilled PA6 and its graphite composite were conducted under inert (N2) blanketing and reactive (air) media. Initially, TGA responses of the fillers were studied and both GNP and G remained stable in N2. The onset of weight loss under N2 blanketing for G and GNP were respectively 820 ± 27.6 °C and 777.3 ± 17.7 °C. At temperature close to 900 °C, G showed relatively poorer thermal stability compared to GNP. A residue of 1.3% for G and 2.0% for GNP were left. The thermal stability of the streams G200/3 and G100/6 remained within a close range thus indicating that varying screw speeds and durations did not play a significant role on influence the thermal stability of the melt processed composites. For the composites, thermal stability were comparable with unfilled PA6, especially in the melt-processed systems, while Some changes occurred in the 2 in situ polymerized systems (20/20 and 40/10) which was ascribed to the presence of small molecules from the catalysing species or unconverted monomers. © 2020 The Authors