PA612 Double Bubble Tubular Film Process – Processability and Structure Development

Abstract

Abstract Biaxially oriented Polyamide 612 (PA612) films made by double bubble tubular film extrusion were characterized. The processing characteristics of the polymer in the double bubble process were investigated. The development of crystallinity and orientation in the films was clearly considered. First bubble PA612 films showed a low level of crystallinity (X = 7.7%). Differential scanning calorimetry (DSC) indicated that the first bubble PA 612 films experienced a considerable increase in glass transition temperature (Tg), cold crystallization temperature (Tc) and crystallinity during aging at room conditions. The second bubble films were more highly crystalline (X = 22 to 28%) with poorly grown β unit cells. The WAXD and SAXS patterns showed that the crystallites of double bubble PA612 films became more perfect by annealing in a boiling 20% formic acid solution, resulting in a well-developed triclinic α crystals coexisting with minor proportion of β phase. The WAXD and SAXS patterns indicated that crystallography planes and lamellae in the second bubble films were oriented depending on SBUR × SDDR (second blow-up ratio x second draw down ratio). White-Spruiell biaxial orientation factors were calculated with the WAXD pole figure data. The hydrogen bonding (0k0) planes of biaxial double bubble films were found by WAXD to be aligned parallel to the sheet surface before and after annealing.