Thermomechanical characterisation of polyamide 6 over a wide range of rates and temperatures

Polyamide 6 is a widely used engineering plastic; however, its thermomechanical properties are not well understood, particularly at medium and high strain rates. In this research, the thermomechanical properties of Polyamide 6 were extensively characterized. Differential Scanning Calorimetry was performed to investigate the glass transition temperature and crystallinity. Frequency sweep Dynamic Mechanical Analysis was carried out through the secondary- and glass-transitions, and the temperature dependent storage moduli obtained from different sweep frequencies were used to construct a master curve. Quasi-static tensile tests at two loading speeds were conducted with digital image correlation for full-field strain mapping. Compression properties were measured at strain rates between 0.001 and 6000 s-1 at room temperature, and temperatures between -60 and 200 degrees C at 0.01 s-1. The mechanical response is highly rate- and temperature-dependent; at large strains and elevated rates, apparent softening occurs owing to heat generation, which was quantified using an infrared camera.