Effects of Pre-stretching on the Physical Properties of LLDPE Stretch Films, 2001 Engineering / Finishing & Converting Conference Proceedings

J. S. Downey, D. Climenhage--Pre-stretching LLDPE films specifically formulated and manufactured for use in roll wrapping applications can significantly improve many of their physical properties which help protect the substrate from damage during handling and storage. Film thickness, cross-sectional area, retained tension, tear strength, cling strength and puncture strength were investigated at pre-stretch levels of 0 to 400%. The thickness of the stretched film was found to be proportional to n ((-0.5) where n is the number of times the film has been elongated. Retained tension was observed to increase with increasing pre-stretch, thus providing greater radial pressure to the wrapped rolls. The ultimate tear strength changed only slightly with increasing pre- stretch, however, much more work was required to produce a tear failure in pre-stretched films. Cling strength had the tendency to decrease at high elongation but would be more than enough to bond the loose end of the film to the underlying wraps. Puncture strength per micrometer of thickness increased with increasing pre-stretch levels. It is believed that these changes in physical properties as a result of pre- stretching can significantly improve roll protection in many different wrapping applications.