Effects of the biaxial orientation on the mechanical and optical properties and shrinkage of polyamide 6-66-montmorillonite-nanosilica nanocomposite films

摘要： Polyamide 6–66 (PA6-66)–montmorillonite (MMT)–nanosilica (NS) nanocomposite ?lms were fabricated through a cast ?lm process and then biaxially stretched on a laboratory stretcher. Uniaxial or biaxial stretching induced the elongated conformation of MMT and NS. The b axis of the α crystals and the amorphous phase were revealed to align along the machine direction (MD) after stretching, with the uniaxial orientation playing a more signi?cant role. Furthermore, the crystallinity of PA6-66 stretching increased with the stretching ratio. Uniaxial stretching gave rise to a signi?cantly enhanced tensile strength along the MD, whereas it slightly decreased the mechanical properties along the transverse direction (TD). In contrast, the ?lms subjected to biaxial stretching exhibited more balanced mechanical properties. Uniaxial and biaxial stretching led to decreased transmittance and increased haze in the PA6-66–MMT–NS ?lms; this could have been due to the elongated nanostructure of the two nano?llers, which inhibited the transmission and facilitated the scattering of visible light. The thermal shrinkage of the ?lms increased with increasing stretching ratio, and the biaxially oriented ?lms presented nearly equal shrinkage in the MD and TD. The addition of nano?llers decreased the shrinkage attributed to the mobility inhibition of the polymer chains during heating. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47504.