Structure-Property Relationship of Biaxially Oriented Polyethylene (BOPE) Films Made via Double Bubble Film Fabrication Process

摘要

Mechanical and optical properties were compared between a double bubble biaxially oriented polyethylene (BOPE) film and a blown film. The double bubble film exhibited higher modulus, higher tensile strength, better optical properties, but lower tear strength. Morphological differences between the double bubble film and the blown film were investigated with differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS). It was found that in the double bubble process the large crystals were broken up into smaller fibrillar crystals with a larger long spacing. C-axis of the fibrillar crystals preferentially lay in the plane of machine direction and cross direction (MD-CD). The lower tear strength for double bubble films has been proposed to be due to the fibrillar crystal morphology. A sample with a larger low temperature melting peak showed a better tear strength with a similar stiffness.