Squeeze flow in multilayer polymeric films: Effect of material characteristics and process conditions

Aghkand, Zahra Kanani; Ajji, Abdellah

doi:10.1002/app.51852

Cited by 3 publications

(3 citation statements)

References 24 publications

(38 reference statements)

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“…With thin seal layers, SOF is only increased at high seal pressure and long seal time if viscosity of seal material is reduced. A 10‐fold seal pressure increases SOF only with thick seal layers 58 …”

Section: Polyolefinsmentioning

confidence: 99%

Seal materials in flexible plastic food packaging: A review

2023

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Flexible packaging has many advantages in the food industry, arising from low weight, formability, multilayer complexity and cost. Heat sealing is a very efficient technique to close flexible food packaging. Currently, many thermoplastic materials are used in seal layers. A seal can be formed when these materials are heated and brought into contact; thereafter, polymer chains diffuse across the seal interface and entangle. Hydrogen bonds, polar and ionic interactions are molecular forces that can come into play, depending on the thermoplastic materials that are used in the seal layer. Bonds between identical polymers, referred to as autohesion, are formed in pouch applications (e.g., horizontal and vertical form-fill-seal packages). In lidding applications, the flexible film is sealed to a rigid cup, tray or bottle, whereby bonds can be formed between non-identical polymers because the materials are often provided by different suppliers. All heat seal technologies imply heating of seal layers but differ in the heating principle. In the food industry and in most scientific seal studies, the seals of mono-and multilayered packaging are mainly formed by conductive heating. Recently, the use of emerging technologies, such as ultrasonic and laser heating, is increasingly described in recent papers. Applied seals are characterized by strength after a specified cooling time. Immediately after heating, this strength is referred to as hot tack. A good seal performance is crucial to guarantee food safety and quality. Besides strength, tightness is important to prevent food degradation, caused by microorganisms and external gases, and to keep aromatic gases inside the package. This review aims to give a literature overview that can support stakeholders in the food industry to improve and optimize the material selection in flexible packaging, in order to obtain seals with desired tightness and strength. Heat seal studies on materials and seal technology of flexible food packaging, such as pouches and lidding films, are considered. Scientific data are categorized from a materials' perspective, based on chemical structure, which is revealed by chemical and thermal analysis. A majority of the seal studies is categorized in a first section on polyolefins as seal layers. The following sections describe the seal functionality of (i) ethylene copolymers, such as ionomers; and (ii) polyesters, such as poly (ethylene terephthalate), pol (lactic acid) and poly (butylene succinate). The role of plasticizers, fillers and other

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Section: Polyolefinsmentioning

confidence: 99%

Seal materials in flexible plastic food packaging: A review

2023

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“…As for the dwell time, it is determined by the material requirements and the speed of the tool. It was also shown that in order to get a good seal, a minimum pressure is needed, however, a higher pressure is ineffective or even detrimental to the seal quality because it causes material squeeze flow 16,17 . T‐peel tests on single layered polymer films showed three types of failure, depending on the mechanical strength of the sealed zone: peeling, tearing and peeling + tearing 14 .…”

Section: Introductionmentioning

confidence: 99%

“…It was also shown that in order to get a good seal, a minimum pressure is needed, however, a higher pressure is ineffective or even detrimental to the seal quality because it causes material squeeze flow. 16,17 T-peel tests on single layered polymer films showed three types of failure, depending on the mechanical strength of the sealed zone: peeling, tearing and peeling + tearing. 14 It was also shown that for complex films, the same failure types were observed, but with 3 different ways for tearing failure: tearing of the entire film can happen at one side of the seal, or only a breaking of the sealant layer, while the third option is the tearing of the sealant layer with a delamination between the sealant and external layer of the films.…”

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confidence: 99%

Influence of process parameters on sealing strength of polymer films in an innovative continuous heat sealing technology

2022

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An innovative process for packaging films sealing has been recently promoted: Heat is provided on the upper side of the polymer films. In this paper, sealing conditions are studied for two PET-PE films. Melting temperature of the sealant layer material was determined by differential scanning calorimetry (DSC), through both conventional and successive self nucleation and annealing procedures. Interface temperature was measured during sealing, and a temperature model was fitted to compute the effective sealing time for each process parameter. Unconventional T-peel tests were established with disk-shaped seal samples. Strengths of the seals formed for different process parameters were measured. Results have shown that the melting temperature measured by DSC (108 C and 99 C for PE70 and PE120, respectively) is the seal initiation temperature of the materials. Results of T-peel tests can be divided in two regions: A growth region where seal strength values increase, up to a threshold at which the seal strength is almost constant (20 N/10 mm). In the growth region, we propose a time-temperature relationship between seal strength, tool temperature, and effective sealing time in the form of an Arrhenius model C exp α T

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Modeling the squeeze flow of droplet over a step

2022

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In this paper, we study the squeeze flow of a droplet confined between two plates in presence of a step. Understanding this fluid mechanics problem is of utmost importance particularly for nanoimprint lithography, wherein the photoresist droplets are dispensed on a substrate, and imprinted and cured into a desired pattern. Often, the desired pattern includes various steps and trenches, the droplets need to flow over. Here, we use the lubrication theory to find the instantaneous pressure and velocity fields. A volume-of-fluid advection algorithm is also used for evolving the volume fraction in time. The obtained results reveal that for step sizes comparable to the gap between plates, the squeeze flow characteristics become quite distinct across the step. Under such circumstances, the fluid finds it less expensive to reverse its flow direction towards the deep region to pass through the low-resistance zone, which leads to a net mass flow rate across the step from shallow to deep region. Such a mass transfer is found to be enhanced by applying larger squeezing forces. This phenomenon becomes less noticeable for liquid film thicknesses much larger than the step size. As a result, it takes large droplets longer time to reach to the regime wherein a substantial mass flow rate occurs. In addition, the results suggest that thedimensionless characteristic features such as the ratios of volume and area of liquid in deep (or shallow) region to those of the total liquid collapse onto their corresponding master curves.

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Squeeze flow in multilayer polymeric films: Effect of material characteristics and process conditions

Cited by 3 publications

References 24 publications

Seal materials in flexible plastic food packaging: A review

Seal materials in flexible plastic food packaging: A review

Influence of process parameters on sealing strength of polymer films in an innovative continuous heat sealing technology

Modeling the squeeze flow of droplet over a step

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