Ionic Liquids Incorporating Polyamide 6: Miscibility and Physical Properties

The effects of 1-vinyl-3-butyl imidazole chloride (VBIM) on the structure and properties of Polyamide 6 (PA6) were investigated systematically. It was found that PA6/VBIM blends were homogeneous without phase separation. The glass transition temperature (T_g) of PA6 increased with small VBIM loadings followed by the decreasing in T_g with further increasing the amount of VBIM. The crystallization temperature decreased with the addition of VBIM because of the strong interactions between VBIM and the PA6 matrix, as well as the dilution effect when large amounts of VBIM was introduced to the matrix. According to rheological testing, small amounts of VBIM enhanced the storage modulus and melt viscosity of PA6. Tensile tests also show an increase in strength and modulus at relatively low loadings of VBIM. The strength of PA6 with only 1 wt % VBIM improved by 108% compared to that of neat PA6. Fourier transform infrared (FTIR) investigations revealed that the ions of VBIM preferred to form hydrogen bonds with amide groups in PA6. Therefore, VBIM acts as physical connection point for the neighboring PA6 molecular chains. The specific interactions between VBIM and PA6 account not only for the enhanced melt viscosity of PA6, but also for the improved mechanical properties. Moreover, outstanding antistatic property was also observed. The surface resistivity of the sample with 1 wt % VBIM was 1.50 × 10¹⁰ Ω/sq, which means good electric dissipation property.