Influence of processing conditions on heat sealing behavior and resultant heat seal strength for peelable heat sealing of multilayered polyethylene films

摘要

The effects of processing conditions for peelable heat sealing of multilayered polyethylene (PE) films on heat sealing behavior and heat seal strength were investigated. Two sets of seal bars, knurled shape and flat shape, were used for heat sealing. After the heat sealing, the sealed portion was cooled using a set of cooling bars. Heat sealing temperature was adjusted to yield the heat seal strength of 4.0 N/15 mm, 6.0 N/15 mm and 8.0 N/15 mm at the heat sealing pressure of 0.4 MPa for each set of heat sealing bars. The heat seal strength increased with the increase of heat sealing pressure for the knurled shape bars, while it was less affected by heat sealing pressure for the flat shape bars. In situ measurements of the sealing bar clearance and interface temperature revealed that the reduction speed of clearance was significantly affected by the pressure for knurled shape bars, while it was almost independent of pressure for flat shape bars. Even though the temperatures set for the similar heat seal strength were different between knurled and flat shape bars, the maximum temperatures at the interface were almost identical. The effect of the shape of seal bars on heat seal strength became less significant after the sterilization process.