The heat sealing of Escal®barrier films

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Abstract
The mechanical properties of a heat‐sealed barrier film, Escal®, used for environmental enclosures in the field of preventive conservation, were investigated. The seals were made using an existing Crossweld® heat sealer. The objective was to determine the optimum settings for the heat sealer in order to produce the best heat seal in terms of its strength and integrity, for example as a barrier to gaseous diffusion. The heat sealer settings consisted of a weld setting and a cool setting. The three independent variables involved were welding temperature, welding time and cooling time. The polymer adhesive layer in the barrier film, which was used to create the seal, was linear low‐density polyethene. A tensile test was used to assess the seal strength, and the integrity was determined by examining peel fracture surfaces with a scanning electron microscope. The results indicated that, under the optimal weld settings, the seal was stronger than the barrier film. Weld setting 3, the optimum value with a weld temperature of 117°C, corresponds to the equilibrium melting temperature of linear low‐density polyethene.