Effects of Liquid Contaminants on Heat Seal Strength of low‐density polyethylene Film

Abstract

Heat sealing is commonly applied for making form‐fill‐seal packages fabricated from thermoplastic films. One of the challenges frequently faced by the industry is inadvertent contamination of film–film interface by the product during filling, which can compromise package seal strength. In this study, the effects of dwell time (0.5–1.5 s), jaw pressure (28–1860 kPa), jaw configuration (narrow versus wide contact area) and jaw temperature (150°C–180°C) on the interface temperature and seal strength of a linear low‐density polyethylene (LLDPE) film were investigated. Three different film–film interface conditions were studied: (1) no contaminant; (2) with water contaminant; and (3) with vegetable oil contaminant. In the presence of liquid contaminant, jaw pressure played an important role in displacing the liquid from the seal area to form intact seals. Short dwell time (0.3 s) and low jaw temperature (150°C) was not favourable for forming intact seals in both water‐contaminated and vegetable oil‐contaminated films. The optimum jaw temperature and dwell time required to produce intact seals for oil contaminated films was 180°C and 0.3 s, respectively, whereas a combination of 165°C jaw temperature and 1 s dwell time was required to form intact seals for water‐contaminated films. Within the experimental conditions investigated, interface temperatures of 130°C–140°C resulted in the most optimum seal strength for both water‐contaminated and clean film specimens. Above 140°C, a weakening of seal strength was observed, presumably because of the change in melt flow characteristics and possible initiation of thermal degradation of the polymer. Copyright © 2011 John Wiley & Sons, Ltd.

Seal Strength Evaluation of Flexible Plastic Films by Machine Testing and Human Peeling

“…In general the seal strength of a heat sealed flexible pouch may vary, and can depend on the types of materials used for the sealing layer, the seal temperature, dwell time and pressure of the sealing jaw [1][2]. Since seal strength is one of the most important quality characteristics for evaluating packaging performance, researchers have attempted to analyze the seal strength of flexible packaging by varying packaging materials or sealing parameters by using standard testing procedures [3][4][5][6][7][8][9][10].…”

Effect of Liquid Contamination on Hermeticity and Seal Strength of Flexible Pouches With Lldpe Sealant

“…It may show seal strength and hermeticity trends on a large scale, but the scope of the study was to test a close range of sealing temperatures and dwell time that would most likely be used in industry. Within the sealing conditions investigated, the optimal seal temperature and dwell time were different than the study completed by Mihindukulasuriya and Lim [9] due to the wide range of dwell time and seal temperatures. However, Mihindukulasuriya and Lim [9] determined that vegetable oil has a slightly lower seal strength compared to water and the control.…”

“…Within the sealing conditions investigated, the optimal seal temperature and dwell time were different than the study completed by Mihindukulasuriya and Lim [9] due to the wide range of dwell time and seal temperatures. However, Mihindukulasuriya and Lim [9] determined that vegetable oil has a slightly lower seal strength compared to water and the control. In addition to the findings of Mihindukulasuriya and Lim [9], this study uses statistical analysis to not only test for a difference between contaminants, but if the difference is significant.…”

“…When in contact with a solid surface, the contact angle θ for water is 89.51⁰ 1.17⁰ and vegetable oil is 29.96⁰ 1.2⁰ [9]. Overall, the contact angle indicates the amount of contamination that comes in direct contact with the film over an area of the film.…”

“…According to Mihindukulasuriya and Lim [9] the liquid contaminant will act as a heat sink by absorbing the thermal energy that passes from the seal jaws through both plies of film. The thermal diffusivity of vegetable oil, 0.09 x 10 -4 m 2 /s at 20⁰C, is lower than water 1.4 x 10 -4 m 2 /s at 20⁰C Mihindukulasuriya and Lim [9]. However, this study uses a salt water solution instead of water.…”