Preparation and characterisation of polyamide-polyimide organoclay nanocomposites

Background: Ternary nanocomposites containing an organomodified layered silicate polyimide additive within a polyamide matrix have been investigated to gain greater insight into structure-property relationships and potential high-temperature automotive applications. Results: Polyamide nanocomposite blends, containing 3 wt% of organoclay, were prepared and compared with organoclay-reinforced polyamide and neat polyamide. Nanoclay addition significantly increased heat distortion temperature, as well as both the tensile and flexural moduli and strength. The addition of polyimide demonstrated further increases in heat distortion temperature, glass transition temperature and the flexural and tensile moduli by about 17, 21 and 40%, respectively. The tensile and flexural strengths were either unaffected or decreased modestly, although the strain-to-failure decreased substantially. Morphological studies using transmission electron microscopy (TEM) and X-ray diffraction showed that the nanoclay was dispersed within the ternary blends forming highly intercalated nanocomposites, regardless of the presence and level of polyimide. However, TEM revealed clay agglomeration at the polyamide-polyimide interface which degraded the mechanical properties. Conclusions: A range of improvements in mechanical properties have been achieved through the addition of a polyimide additive to a polyamide nanocomposite. The decrease in ductility, arising from the poor polyamide-polyimide interface and nanoclay clustering, clearly requires improving for this deficiency to be overcome.