Modeling and experimental analysis of squeeze flow of sealant during hot bar sealing and methods of preventing squeeze-out

Morris, Barry A.; Scherer, Jonathan M

doi:10.1177/8756087915578183

Cited by 11 publications

(24 citation statements)

References 11 publications

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“…If the amount of squeeze-out increases, adequate sealing cannot be supplied and the defects occur in the sealing region. 46 That is why using sealants that have a wider process window or applying a precise temperature control is critical to prevent sealing failures.…”

Section: Factors Behind the Heat Sealing Problemsmentioning

confidence: 99%

“…As a result, squeeze-out increases linearly with increasing pressure because the extra force will push out the molten sealant easily from the sealing area. 46…”

Section: Pressurementioning

confidence: 99%

“…In that case, increasing the shear rate via changing seal bar design can cause a dramatic decrease of polymer viscosity, and that may raise the squeeze-out problem at the seal interface. 46 Also, different crimp angles might alter the pressure distribution and create different stretched regions within the sealing area. Even if this factor has not been clearly understood yet, some studies are pointing to its importance.…”

Section: Seal Bar Designmentioning

confidence: 99%

“…Moreover, it has been known that there is a small amount of shearing and stretching that occurs in the sealing area due to the patterns of grooved seal bars. 46,47 Even though the film tension is an unavoidable part of the packaging process, its effects at molecular level on seal formation mechanisms are still unknown.…”

Section: Film Tensionmentioning

confidence: 99%

“…Nonetheless, the rheology of melt polymer during the sealing can be arranged by changing the process temperature depending on the polymer characteristics. 46 As an example, Morris 58 indicated that ionomers show less squeeze-out than the plastomers at low sealing temperatures. This feature is coherent with the high viscosity of ionomers at low temperatures and low shear rates.…”

Section: Rheologymentioning

confidence: 99%

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Understanding the factors affecting the seal integrity in heat sealed flexible food packages: A review

et al. 2021

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Seal area represents the most problematic part in food packaging for controlling the moisture and gas ingress and preserving product quality. Understanding the mechanism of heat sealing, which is a widely used method in flexible packaging, is critical for maintaining product quality throughout the storage and preventing food waste.Likewise, understanding the factors causing the leak formation in the seal interface helps to avoid failures and increase integrity for all seal types produced by heat sealing methods. This review looks at heat sealing and its mechanisms in flexible food packaging materials and particularly focuses on the reasons behind the encountered seal integrity problems that have a detrimental effect on food quality and shelf life.Heat sealing mechanisms, form fill seal systems and seal types were analyzed. Then, factors affecting the leak formation have been grouped as process parameters, material properties, contaminants, and further processes, which is uncharted territory in open literature. Finally, the details of these groups and their interrelationships were examined and discussed. Revealed key factors as shown in this study are expected to guide future research for understanding leak formation mechanisms in flexible food packaging.

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Section: Factors Behind the Heat Sealing Problemsmentioning

confidence: 99%

“…As a result, squeeze-out increases linearly with increasing pressure because the extra force will push out the molten sealant easily from the sealing area. 46…”

Section: Pressurementioning

confidence: 99%

Section: Seal Bar Designmentioning

confidence: 99%

Section: Film Tensionmentioning

confidence: 99%

Section: Rheologymentioning

confidence: 99%

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Understanding the factors affecting the seal integrity in heat sealed flexible food packages: A review

et al. 2021

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

Aghkand

Ajji

2021

J of Applied Polymer Sci

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In this work, effects of sealing temperature, time, pressure, as well as sealant thickness and viscosity on squeeze out flow (SOF) in heat sealing were examined. A new image analysis approach is presented to quantify SOF in heat sealing. It was found that increasing temperature or pressure could improve SOF but only in thick 130 μm sealants and reducing the sealant thickness to 50 μm suppressed SOF. Reducing viscosity in 50 μm sealant films was also found to improve SOF only at high-sealing pressure and long sealing times. Three approaches were used to model SOF: analytical one-dimensional model, numerical one-dimensional model using finite difference method (FDM), (iii) Numerical two-dimensional model using finite element analysis. Heat transfer was modeled, and it was shown that heat transfer induces a delay in SOF. When the FDM and the heat transfer models were combined, a good agreement between experimental and model prediction could be obtained. In addition, modeling results showed that SOF occurred in shear rates within the transition region between the Newtonian and Power-law regions. This indicates the importance of considering the Carreau-Yasuda fluid behavior in modeling of SOF.

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Estimating minimum required dwell time for the heat sealing of talc containing polypropylene/low‐density polyethylene packaging films

et al. 2023

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Dwell time is one of the main parameters influencing heat seal quality and process efficiency in flexible packaging. In this study, the rheological behaviour of polypropylene (PP)/low-density polyethylene (PE-LD)-based compound films containing different ratios of talc was examined. The minimum dwell time required to supply a sufficient sealing was estimated based on heat conduction time and reptation time.Reptation is a rheological concept used to described the behaviour of a polymer melt, and the reptation time is the time required for a molecule to escape from its surrounded entangled structure. The results showed that increased levels of talc are associated with elevated complex viscosities, storage and loss modulus as well as an increased seal strength. The estimated minimum required dwell time at the seal initiation temperature (SIT) dropped sharply with the initial introduction of 10 wt% talc.However, increasing the talc ratio to 30 wt% did not create any major change in the estimated time value. Also, observed T-peel strength values for 0.1 and 0.5 s dwell time at SIT confirmed the predicted minimum required dwell time values. On the other hand, when the seal temperature is increased to the higher end of the operation window, time estimations did not match with the observed seal strengths. Here, the melting already starts and the molecules diffuse up to a certain distance before the interface temperature reaches the desired level. Recalculation of the average diffusion distance by including this pre-melting situation can present a better approach for the temperatures above SIT. When the molecules diffused around halfway along the sealant thickness observed, seal strengths reached a sufficient level (2.5 N/25 mm) for both SIT and the highest end of the operation window. In conclusion, it has been revealed that knowing the reptation time and the required time for the heat conduction during the sealing process can help to predict the minimum required dwell time to achieve quality sealing, especially at low sealing temperatures.Additional surface characterizations also helped to elaborate on the influence of changing insoluble filler ratio on the seal initiation properties. It has been showed that the added talc increases the surface free energy and supplies easier wetting at

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Modeling and experimental analysis of squeeze flow of sealant during hot bar sealing and methods of preventing squeeze-out

Cited by 11 publications

References 11 publications

Understanding the factors affecting the seal integrity in heat sealed flexible food packages: A review

Understanding the factors affecting the seal integrity in heat sealed flexible food packages: A review

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

Estimating minimum required dwell time for the heat sealing of talc containing polypropylene/low‐density polyethylene packaging films

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