Characterisation of heat-sealing part of laminated oriented nylon and polyethylene films

Abstract

In order to clarify the relationship between heat-sealing conditions and the strength of the heat-sealed part, the crystalline structure of the heat-sealed part of the film was evaluated by differential scanning calorimetry (DSC) and Fourier transform infrared (FT IR) spectroscopy. The laminated films that include a biaxially oriented nylon (ONY) film and a cast linear low-density polyethylene (LLDPE) film with an appropriate adhesive were heat-sealed by using an impulse type heat-sealer. First the possibility of adhesion was examined by changing the processing conditions and the maximum temperature was measured. As for mechanical properties, a peel strength test was performed to evaluate the strength of the heat-sealed parts. However, the strength could not be evaluated by the peeling test alone, because the fracture shifted from the heat-sealed part to the edge of the heat seal accompanied by necking and yielding of the film. In order to solve this problem, a tensile specimen with a semicircular notch was proposed to evaluate the strength of the heat-sealed part. Tensile strength increased with increasing crystallinity of the LLDPE indicated by the melting peak in the DSC measurement and FT IR spectra. It was found that crystallinity profoundly affected the mechanical properties of the heat-sealed part.