Heat sealability of laminated films with LLDPE and LDPE as the sealant materials in bar sealing application

Abstract

The heat sealability of laminated films with linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) as the sealant materials was investigated. A laboratory heat sealer was used to study the response of laminated films to temperature, time, and pressure. Platen temperature was confirmed as primary factor in controlling heat-seal strength. Dwell time must be sufficiently long to bring the interfacial temperature to a desired level. When the desired heat-seal strength has been achieved, further increase of dwell time did not improved heat-seal strength. Platen pressure had little effect above the level required to flatten the materials for good contact. Bar sealing process window for each sample were developed. The optimum combination of platen temperature and dwell time for each laminated film can be obtained in the respec-tive process windows. Strength of heat-seal and its failure modes are closely related. Plateau initiation temperature closely corresponds to the final melting point of sealant materials. Relatively higher platen temperature was required to seal laminated films with lower thermal conductance. Required dwell time corresponds closely to the heat flow rate of bar sealing process. Laminated films made from extrusion lamination process provided lower level of achievable heat seal strength when compared with the laminated films made from dry-bond lamination process.

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 bar sealing parameters on OPP/MCPP heat seal strength

“…Therefore, proper control of process parameters such as platen temperature, dwell time and pressure based on the characteristics of each laminate film is important to ensure that the pouch is leak-free and can withstand maximum loading during handlings. In packaging, the term 'acceptable heat seal' refers to the heat seal that when subjected to loading, will break at the laminate film instead of at the heat seal [2]. In other words, the strength of the heat seal is greater than the strength of the laminate film.…”

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

“…Yuan et. al [5] tested a similar structure to what is used in this study, Polyethylene-Terephthalate, PET (film laminate) and linear low-density polyethylene, LLDPE (sealant layer). An increase in seal strength occurred from 0.1 seconds to 1 second dwell time for the majority of sealing temperatures within the range of 103⁰C and 130⁰C.…”

“…The pressure applied to seal both sides of the film together will remain the same throughout the study. Pressure is needed to seal two film surfaces together, but increasing the pressure has no effect on seal strength [4,5].…”

“…According to Yuan et. al [5], a sealing temperature of a few degrees before the melting temperature, T m , seal strength will significantly increase and result in a peel, delaminating a tear mode or combination of the failure modes. If the sealing temperature is more than a few degrees below the melting point, then a peel failure mode will more likely occur and the result will be a lower strength than the other failure modes.…”