Effects of anhydrites before and after modification as well as their contents on the thermal and mechanical properties of polyamide 6/anhydrite composites

The anhydrite (AII) is treated with different methods: calcination (c‐AII) and surface modification (c‐AIIg, AIIg) by γ‐glycidoxy‐propyltrimethoxysilane (GPS), and the polyamide 6 (PA6)/anhydrite composites are prepared by a twin‐screw extruder. The effects of different anhydrites as well as their contents on the thermal and mechanical properties of PA6 composites are studied in the present work. Fourier transform‐infrared spectroscopy and X‐ray photoelectron spectroscopy demonstrate that the active GPS chains are chemically tethered onto the surface of the anhydrite. The differential scanning calorimetry measurements indicate that different anhydrites act as a heterogeneous nucleation agent in PA6 matrix and lead to the appearance of new γ‐PA6 crystalline form. Thermogravimetric analysis suggests that the addition of anhydrite after calcination or surface modification has little effect on the thermal stability of the composites. Moreover, it is found that the impact strength of the composites is decreased with the increasing content of different anhydrites, while the tensile strength is increased with the increase of c‐AIIg and AIIg content and the most significant improvement of the tensile strength of PA6/c‐AIIg and PA6/AIIg composites is obtained when the content of c‐AIIg and AIIg is 15 wt%, respectively. POLYM. COMPOS., 37:2360–2368, 2016. © 2015 Society of Plastics Engineers