Optimizing spin-coating of polyamide-6/CNC nanocomposites with improved mechanical properties

The Taguchi design was performed to determine the influence of five factors, namely Cellulose nanocrystal (CNC) loading (A), solution concentration (B), first sonication time after adding CNCs (C), second sonication time when polyamide-6 (PA6) is completely dissolved (D) and rotation speed (E) on the mechanical properties of (CNCs)-reinforced PA6 thin films (CNC-PA6). These nanocomposites were prepared by solvent mixing in formic acid (FA) and subsequent spin-coating. According to L18 orthogonal array, the present study demonstrated that CNC loading (A) is the most significant control parameter for both, Young's modulus and tensile strength. The optimum parameters were CNC loading 1wt.%, solution concentration (10 wt./v.%), first sonication time (30 min), second sonication time (60 min) and rotation speed (5000 rpm). The films obtained with these parameters exhibited higher Young's modulus and tensile strength. The effect of other factors was negligible, except for rotation speed, its influence on mechanical properties was relatively significant at 1 wt.% CNC loading and above. A smooth and uniform surface and well dispersed CNCs were obtained for the film spin-coated at higher rotation speed. These results were elucidated and proved with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Finally, differential scanning calorimetry (DSC), was performed for films produced with different CNC loading while other factors were kept at their optimum levels. The findings collected from DSC indicated that CNC loading did not impact the crystallinity of the films despite its tremendous effect on mechanical properties.

Automated summary

The Taguchi design was used to investigate the effects of five factors on the mechanical properties of CNC-reinforced PA6 thin films. CNC loading was found to have the most significant influence on Young's modulus and tensile strength. Optimum parameters were determined as CNC loading 1wt%, solution concentration 10wt/v%, first sonication time 30 min, second sonication time 60 min, and rotation speed 5000 rpm. SEM, TEM, and DSC were performed to confirm the results and understand the effects of CNC loading on crystallinity and mechanical properties.