Application of single site catalyst metallocene polyethylenes in extruded films: Effect of molecular structure on sealability, flexural cracking and mechanical properties

Sadeghi, F.; Ajji, Abdellah

doi:10.1002/cjce.21964

Cited by 5 publications

(23 citation statements)

References 18 publications

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“…This can be a result of the presence of plastomer in the lower 15 μm of the seal layer. Compared with film 1, the peak value (0.43 ± 0.03 N mm −1 ) is high, suggesting more and/or deeper entanglement, this was previously described in literature . For both films, the hot tack strength decreases strongly in a similar way at elevated temperatures (greater than or equal to 150°C).…”

Section: Resultssupporting

confidence: 72%

“…This spring back effect is similar when wrinkles are present. The effect is discussed in several papers . Figure shows the hot tack results of all films.…”

Section: Resultsmentioning

confidence: 95%

“…In scientific and technical papers, several tests are performed on packaging films with contaminated seals such as seal strength, leak rate, and degree of particle encapsulation (caulkability) . This study is focussed on seal strength.…”

Section: Introductionmentioning

confidence: 99%

“…This study is focussed on seal strength. Hot tack tests are performed to evaluate the resistance of packaging films against spring back forces . The relation of seal through contamination and hot tack performance is part of this study.…”

Section: Introductionmentioning

confidence: 99%

“…The relation of seal through contamination and hot tack performance is part of this study. In the last decades, the influence of seal material composition on the contaminated seal performance was the topic of a limited amount of studies, and these studies did not include a well‐described application method for solid contamination . Moreover, there are no methods described in these studies to obtain the optimal or maximal seal performance through contamination.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation and optimization of seal behaviour through solid contamination of heat‐sealed films

et al. 2019

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A method is presented to apply solid powder/granulate contamination (ground coffee and blood powder) in between the heat conductive seals of flexible packaging materials. A response surface method is tested and validated to optimize seal strength of heat conductive sealing with and without solid contamination. In this study, a maximal seal strength is defined as optimal. Using these methods, three typical packaging films with varying seal layer composition (metallocene linear low‐density polyethylene (LLDPE), plastomer, and sodium ionomer) are maximized towards contaminated seal strength. Contamination caused a decrease in seal strength and narrowed down the process window (seal temperature and time combinations) in which at least 90% of the maximal strength is obtained. The influence of seal layer composition on the clean and solid (ground coffee and blood powder) contaminated seal performance (seal strength, process window, and leak tightness) was evaluated. The film with the plastomer‐based seal layer outperformed the other films with respect to the width of the process window. It also reached a higher seal strength and a higher amount of leak tight seals (evaluated with the dye penetration test) after optimization. The hot tack test was evaluated as predictive test for the contaminated seal strength. The results of this study do not support an indicative relationship.

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Section: Resultssupporting

confidence: 72%

“…This spring back effect is similar when wrinkles are present. The effect is discussed in several papers . Figure shows the hot tack results of all films.…”

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evaluation and optimization of seal behaviour through solid contamination of heat‐sealed films

et al. 2019

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Polyethylenes in blown films: Effect of molecular structure on sealability and crystallization kinetics

Moreira

Dartora

Santos

2016

Polymer Engineering & Sci

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Three types of polyethylene (PE), with different molecular structure, were selected and used in the production of films using a semi‐industrial blown film extrusion line. Carbon nuclear magnetic resonance and crystallization analysis fractionation tests were performed on the PE polymers to assess their molecular structure. Sealability properties of the films, as well as crystallization kinetics, were evaluated and the results are discussed according to the molecular structures of the polymers. It was found that distribution of short chain branching (average comonomer sequence nH or nO) on the backbone of the PE chains are the main factor controlling the beginning of sealability. The completely random placement of the comononer on the polymer backbone (monomer dispersity 100%) generated crystals with smaller size and a lower melting temperature. Sealing was controlled by crystal distribution, chain diffusion, and entanglement formation at the interface. PE with lower melting point and linear molecular structure showed greater hot tack strength. PE with long chain branching showed a delay on seal process leading to lower sealing speed. POLYM. ENG. SCI., 57:52–59, 2017. © 2016 Society of Plastics Engineers

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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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Application of single site catalyst metallocene polyethylenes in extruded films: Effect of molecular structure on sealability, flexural cracking and mechanical properties

Cited by 5 publications

References 18 publications

Evaluation and optimization of seal behaviour through solid contamination of heat‐sealed films

Evaluation and optimization of seal behaviour through solid contamination of heat‐sealed films

Polyethylenes in blown films: Effect of molecular structure on sealability and crystallization kinetics

Seal materials in flexible plastic food packaging: A review

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