Orientation,Structure and Properties of Double-Bubble Oriented Lldpe Films

Abstract

Biaxially oriented linear low density polyethylene (LLDPE) films are produced using the double-bubble process with different machine direction (MD) orientation levels and the same transverse direction (TD) blow-up ratio. Their mechanical behavior is characterized in terms of the tensile strength and tear resistance. The microstructure and orientation are characterized using microscopy, x-ray diffraction (XRD), and Fourier transform infra red spectroscopy (FTIR). The results indicate that MD tensile strength increases with increasing MD stretching (draw) ratio while the TD tensile decreases. Tear resistance remains mainly constant in TD and decreases in MD with increases in draw ratio. Morphology analysis reveals that overstretching lamellae tend to align perpendicular to MD with an increase of their lamellar dimensions. c-axis orientation of lamellae in MD increases with draw ratio while a-and b-axes orient towards normal direction (ND) and TD respectively. A good correlation is observed between c-axis orientation and MD tear resistance and tensile strength.