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Scratch behavior of extrusion and adhesive laminated multilayer food packaging films.

by:Top-In     2020-08-02
Foreword multi-layer flexible polymer film has been widely used in food, agriculture, medicine, electronic packaging and other fields.
In the process of multi-layer film production, lamination is usually used to glue multiple membrane nets together.
The most common method of lamination is bonding, extrusion, and lamination.
In many packaging applications, it is essential to maintain the structural integrity of the film in order to prevent the loss of the product.
Therefore, the loss of profits.
During the filling, transportation and processing phase of the product cycle, the film must be able to maintain its structural integrity in order to maintain sterility, freshness, product appearance or other key attributes.
One of the main problems is the failure of the membrane puncture, resulting in loss of barrier performance, packaging integrity and/or pressure change.
Due to the limitations of the laboratory test methods of most packaging films and the lack of direct correlation between laboratory test results and field performance, accurate puncture resistance tests were performed on production lines in a factory or pilot environment
This is time consuming and produces a lot of products.
Therefore, there is a need to develop a laboratory testing approach that is relevant to better real-world performance.
In addition, in order to better understand the puncture mechanism, the film of different lamination methods is evaluated on one layerby-
The layering after the damage will be very helpful.
The ability to understand more clearly the contribution of each layer of the film to its anti-damage ability contributes to the design and optimization of the laminated film to develop a better anti-puncture film.
A lot of research has been done before to develop an objective standardized test method to determine scratch resistance in bulk polymers (1-7).
In addition, work has been carried out to understand the effects of different material properties and test parameters and how they affect the scratch behavior of various polymers, including additives (4), (5), (8), (9)Test rate (10),temperature (11)Humidity (12).
Combined with the above research, the two blocks (13-15)
Coating System (16-21).
These results have proved useful for understanding scratch behavior in bulk and coating systems.
Understanding how independent polymer packaging films respond to similar approaches remains a relatively new concept.
Our previous work highlights the lack of applicability of many existing test procedures in reflecting the performance of real-world packaging films.
These test methods include stretching, slow puncture, Elmendorf tear, and Gelboflex test (22).
Damage to similar scratches was observed on many food packaging films, and it was found that the conventional laboratory tests of these films were not necessarily related to the field test results of the mechanical integrity of the film during filling, transportation, and the processing process. Hare et al.
Continue to modify and verify the applicability of the standardized ASTM/ISO scratch test method (22-24).
Scratch test parameters and film properties were tested, including scratch rate, backing material, fixtures for fixing the film, film side and film orientation.
The results show that the developed method can provide consistent and quantitative results for packaging films related to field performance data.
In addition, the damage seen in the scratch test is related to the damage observed on the packaging used on site.
On the basis of this method, Hare et al.
Two food packaging films were tested in an attempt to correlate field performance with scratch performance and layered performanceby-
Analysis by using the developed Cross-layer microscope
Slicing and imaging procedures (25).
It is found that due to the progressive loading properties of the above test methods, the modified scratch test can be used to effectively evaluate the response of various loads and damage types to the scratch test by placing an order layer (25).
Studies have shown that for the film system tested, films with excellent scratch properties are closely related to a given field performance and exhibit excellent layer adhesion and integrity throughout the scratch test, since all layers contribute to the distribution of stress throughout the layer (25).
It is clear that the developed scratch test method provides multi-functional test parameters that can be used to provide similar conditions for the situation that the product will see in field use, and after that provided obvious advantages over other test methods
Test analysis scan by cross execution
And portrait
Slices of damaged samples.
Specifically, because the scratch test applies progressive loads on a specified length, a single test sample can be analyzed at many locations of the scratch path, so it can be analyzed at different load levels.
The evolution of in-layer damage can be visualized and analyzed to determine the advantages and disadvantages of engineering film structures, which cannot be done by other commercial testing methods at present.
In these experiments, the experimental model Film system provided by a major food packaging company was used. EL)
Laminated film and adhesive (AL)film.
The two films have similar structures through which a proprietary set of extruded olefin sealing layers are combined with metal-oriented polyethyleneterepthalate (metalizedPET)layer.
The two films use the exact same closed layer, and the only difference between them is the processing method they attach to the metallized PET layer.
The adhesive laminated film system uses a set of sealing layers that are connected to the metallized PET by adhesive amino groups, resulting in a middle layer between the seal and metallized PET to facilitate adhesion.
The extrusion laminated film system uses the same set of sealing layers that are bonded with the metallized PETlayer, and in the process of extrusion through a set of molds, a combination of heat and pressure is used.
Abnormal thickness of adhesive laminated film [98 [micro]
M, and the nominal thickness of the extruded laminated film is 106 [micro]m.
A schematic diagram of the film can be seen in Figure 1. 1.
The length of the scratch sample is cut to 6 \", 2. 5\"in width (15. 24 x 6. 35 cm).
The scratch test was performed on a four-generation rowing machine made by Surface machine Systems.
Use at least eight samples per test.
Scratch test method scratch test follow standard scratch test method ASTM D7027-
05/1 S0 19252: 08 (26), (27).
Although the machine is similar to the linear increase load setting, the method has been modified to accommodate the test of the independent packaging film (22), (25).
Since the scratch test variable has a significant effect on the behavior of the film, the test variable is selected to obtain consistent and reliable results.
Use a pneumatic fixture to fix the film on the padded material by drawing a vacuum of 86 baipa below the sample, allowing ambient air pressure to uniformly fix the film on the entire surface.
The backing material used is poly (
The scratch length is set to 100mm and the scratch speed using 1-1 is 1 mm/s
Spherical stainless steel tip with diameter mm.
The scratch speed is selected to correspond to the product processing speed expected in the field service.
The film was tested on the outer surface of both machine directions (MD)
And horizontal (TD)
Film direction.
The linear load range for scratch testing is set to 1-15N.
The final load was chosen to create a puncture between about 50% and 75% of the total scratch length.
Scratch damage analysis, such as scratch behavior of bulk polymers
When testing the film on a hard padded material, the sliding behavior is observed, relative to the stiffness of the film (28-30), (25). Jiang et al.
It is shown that although the scratch tip is designed to move at a constant speed, due to the friction between the tip and the material and the limited spring constant of the load cell used to measure the friction, the actual tip speed oscillates (31).
The scratch tip causes the material to deform, allowing the material to accumulate before the scratch tip under normal load.
When the stored strain energy exceeds the additional resistance generated by the accumulation of the material, the tip moves to hinder the material.
This process will be repeated, resulting in periodic rods. slip behavior. Hare et al.
Showed the stick.
By means of an optical microscope, it is easy to observe the sliding behavior on the film surface similar to the structure used in this work (25).
Examples of puncture were visually identified and confirmed using the Olympus BX60 optical microscope.
Use a millimeter scale ruler to measure the length of scratches that occur during puncture.
Then record the load of this measurement point directly from the output of the scratch.
The puncture load used in this work is the average of at least eight samples used by each film system. Cross-
Segmentation imaging of the sample is performed in a similar manner to the previous report (25)
, Thus separating the scratch damage from the test sample, resulting in about 10-mm wide by110-mm long.
The isolated part is then placed on the glass cutting surface, the metallized PET layer is in contact with the glass, and then the adhesive layer is placed up.
The fresh razor blade cools in liquid nitrogen and then goes straight through the sample perpendicular to the scratch direction, resulting in cleancross-
Part of the area of interest.
These individual parts are stable in the clay model during the use of Keyence VK imaging
9700 purple laser scanning co-Focusing microscope (VLSCM).
Harriet Al\'s previous job
It has been shown that this slicing method does not introduce the damage facts that may affect the scratch damage analysis (25).
Results and discussion of scratch test results.
The scratch performance of the two films is shown in the figure. 2.
As shown in the picture, there are obvious differences between films.
The extruded laminated film shows the maximum load required to produce the puncture of both systems.
This shows that ELfilm exhibits excellent mechanical integrity between metallized PETand sealant layers, and therefore is able to distribute these labels better
Stress caused by its structure.
Scratch damage observation on the surface of the external film.
Since the film systems tested here have the same structure, they deform in a similar manner and when viewed from the top of the scratch path, exhibit similar damage features.
A microscopic examination was performed to show the main damage features and their transformation during scratches.
The representative features shown come from the EL system, but are also applicable to the AL system.
A slight scratch damage will be seen at the beginning of the test, as shown in the figure3.
However, due to the low load involved at this stage of the test, coupled with the stress distribution of the soft multi-oil sealing layer, it is not easy to observe damage within the layer.
Any visibility of the top scratches--
At the earliest stage of the test, the downward observation may be due to an increase in surface roughness of the metallized PET layer, which is known to result in an increase in light scattering, resulting in an increase in scratch visibility (8).
As shown in the figure, smooth ironing deformation becomes obvious with the increase of normal load3a.
Smooth ironing deformation transition to large scale
Sliding behavior as shown in the figure
3b, when the tip moves, the obstruction caused by the accumulation of film in front of the tip.
The accumulation of this material leads to the tensile stress at the bottom and behind, similar to the model of Jiang et al. (32).
Then arrive at a point where the tensile stress caused by the scratch tip pulls the relatively hard metallized PET layer apart and then pierces the glue coating as shown3c. Cross-
Refer to the section view of the sample. Cross-
Segmentation imaging of scratches
The damaged film system enables us to conduct an in-depth investigation on alayer. by-
The difference between these film systems during scratches depends on their handling conditions.
Development and Use of slicing methods for imaging scratches
The damaged sample is imaged using a newly cut sample without the need to embed the sample in epoxy resin and polishing like an optical microscope sample preparation.
By eliminating the need for embedding, the softerpolyolefin layer is not subject to the heat generated by the curing process of epoxy embedded compounds, thus preventing potential stress relaxation.
The above method uses a razor blade cooled in liquid nitrogen.
The frozen blade is used to provide accurate cutting, and by reducing the temperature of the olefin layer at the interface with the blade, thereby increasing its modulus and strength, minimizing possible plastic deformation.
Image of undamaged sample can be seen in Figure 14.
As can be seen in the image, each system has a clear layer dividing line, maintaining good layer integrity, without crushing or obvious deformation due to the slicing process. Cross-
Cross section diagram of surface scratches. Scratch-
Many points on the scratch path are sliced and imaged on the damage samples to better understand the damage evolution during the scratch process.
The sample is taken from the smooth deformation area, the early part of the rod
Late part of sliding area and bar-
Slide Area before puncture.
These sections describe well how the film responds as normal loads increase, and how each layer contributes to scratch performance.
Observable layerto-
The layer damage between the TD and MD directions of the two film systems is similar.
The image can be seen in the figure.
EL system and figure 5.
AL system. As seen in Fig.
5, the EL system showed excellent layer adhesion and integrity throughout the testing process.
It can be seen in the figure.
5b, even in the position where the scratch height is deformed, such as the edge, the metallized PET layer remains bonded to the olefin seal layer.
Again, during the night stickSlip phase diagram
SC, the ELsystem maintains its integrity, thus distributing scratch damage in the alarger area.
In fact, the damage through these layers seems to be more uniform than the distribution of other model systems, because all layers react to the stress that is applied to them during the test. As seen in Fig.
6, the AL system does not maintain the same integrity as the EL system during testing.
In the smooth deformation stage
6a, the adhesive laminated film looks similar to the EL film, but the difference becomes more obvious as the damage progresses.
In the early stages of Persistenceslip, Fig.
6b, there is a local layering between the metallized PET layer and the sealing layer, especially at high strain positions such as the edge of the scratch path.
Failure of adhesive layers at these points does not allow the induced stress to be transferred directly to other layers in a consistent manner during scratch testing, again focusing the damage in a small area.
This is also evident in the side Rod process --Slip phase diagram
6c, where these adhesive layer failures grow and continue to lead to concentrated damage areas directly below the insurance tip.
This study highlights the difference in scratch behavior of two highly similar packaging film systems formed under different lamination conditions.
Scratch testing was able to divide these systems in quantitative and recurrent regions, and provided valuable insights into the effects of different layering methods on the structural integrity of the film layer under scratch damage.
It is clear that, through this test, weak structure and poor layer integrity will result in poor scratch performance.
It can be seen that the stress distribution between layers can better resist puncture and film failure, and the stratification between layers will concentrate these stresses, resulting in premature failure.
Scratch testing provides an obvious advantage of being able to conduct an in-depth analysis of each of its layers after damage to the afilm.
In addition, due to the progress of the developed method, damage can be observed from a large number of loads, so that the evolution of intra-layer damage can be observed.
This allows packaging engineers to selectively quickly and effectively identify the advantages and disadvantages of their adhesive film structure and adjust the lamination process accordingly.
This study highlights the excellent strength shown by the extruded laminated film compared to its weak bonded laminated film.
The tip used in these experiments is 1-
Spherical tip of mm stainless steel.
However, different tip geometry and material types may lead to different film properties.
Similarly, different backing materials can also lead to different behaviors, such as neoprene.
Compared to the rigid backing, the neoprene can be used to simulate the Air backing in the packaging product.
This may change the behavior of the film under load by reducing the deformation resistance of the scratch tip, resulting in completely different scratch behavior and performance.
The test variables selected for this work are selected not only because they apply to products used in the field, but also because they have results and image quality compared to other tips, backgrounds and scratch speeds
Because of this, the results given here are consistent from one sample to another and can be used for more detailed and reliable analysis.
Although there are limitations, the scratch test method provides significant flexibility test conditions to meet the requirements of the mechanical integrity assessment of the packaging film and the optimization of the laminated structure design.
Conclusion The scratch test method has been used to evaluate a set of two packaged films that laminate custom PET using the same PE-based closed layer by adhesive lamination and extrusion lamination methods.
Test results obtained directly from scratch are combined with Cross
Segmentation imaging of scratchesdamaged films.
The results show that the stronger layer integrity obtained by the extrusion lamination transformation method provides excellent stress redistribution and subsequent excellent scratch performance.
Scratch testing offers unique advantages over other film testing methods. It allows post-
Test analysis of test samples on layer-by-
Due to the progressive loading nature of the atch cratch test, it is layered under a wide range of loading conditions.
This approach can be an effective tool to help package movies and even provide feedback to guide the design of multi-layer films.
Special thanks to Allan Moyse for making materials and components for this study.
Corresponding: RedJue Sue; e-
Email: tamsue @ tamu
Edward contract Grant sponsor: consortium for polymer scratch behavior at Kraft Food, defense logistics and TAMU. DO! 10. 1002/pen.
23544 online release in the Wiley Online Library (
Wileyonlinelibrary. com). [C]
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Panoskiniakis (2)(1. )
Department of Mechanical Engineering, Polymer Technology Center, Texas A & M University, Texas University station 77843-3123(2. )
Kraft Foods Global
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