Over seven million tons of polyethylene-coated paper products are manufactured every year, making PE the most used coating agent for paper packaging.
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The popularity of PE comes from its effectiveness and cost-effectiveness, which is hard to match with other materials.
So, let’s look at what poly-coated paper is and understand why it is the most popular paper coating solution globally.
As the name suggests, PE coating paper is a paper roll coated with polyethylene to make the paper water and grease-resistant.
The coating substance (PE film) is heated up and made into a thin film no more than 0.04cm thick. The hot film is then pressed onto the surface of the paper board to create a layer. This process will make a tricky coating hard to strip off the paper.
So the resulting polyethylene-coated paper is water-resistant and sturdier, making it perfect for manufacturing all types of food packaging.
Polyethylene is made from sources that come from natural gas and crude oil. The process involves creating multiple reactions of ethylene molecules in the presence of a catalyst.
This reaction breaks the double bond of the molecules and helps the carbon atom connect to the chain. The length of the chain defines the molecular weight of the resulting material.
The thickness of PE coating paper is calculated in grams per square meter. The higher the GSM number, the heavier the paper due to its thickness.
Generally, the quantitative thickness of PE coating used on paper is 10-20 GSM.
However, the required thickness of PE coating changes according to various requirements.
Some common examples that can help you choose the correct quantitative thickness of PE coating appropriate for your purposes are mentioned below:
As mentioned earlier in this article, different paper applications require a different thickness of PE coating to be effective.
Following that same point, you need to put a different thickness of PE coating on various paper types as well. Some examples are mentioned below.
Matte Finish Treatment
Matte PE film is used for making high-quality product packaging labels that have impeccable sharpness and uniformity for the print on top of it.
Whether it is for printing labels of cold drinks or grocery items, matte PE film can be used to create visually attractive labels that are vibrant.
Matte PE film has a non-reflective surface, which allows the labels to be very easy-to-read and detect even in the middle of other products.
Glossy Finish Treatment
Glossy PE film is used for making various types of packaging products, mainly products like PE-coated paper cups.
It provides excellent water and moisture protection, making the cups very effective.
Apart from food packaging, glossy PE film is also used for making bright and shiny packaging that can draw the attention of onlookers and help products stand out.
Single Side PE Coated Paper
Single side PE coated paper has plastic coating on paper only on one side. It is used for making disposable food packaging containers.
The insides of the container are coated with PE to make the container water and moisture-resistant and sturdy and resistant to tearing.
However, the PE-coated side is also not great for printing branding information, which is also why customers choose double pe coating if they have a great demand on printing quality
Double Side PE Coated Paper
Double-sided PE coated paper is mainly used for disposable cold food packaging, namely ice cream cups. Just like single side, PE coated paper; the insides are coated to make the paper water and moisture resistant.
However, the outer layer needs to be covered with pe film in the paper container used to serve cold drinks.
Double pe coating is done to ensure that the cup does not crumble upon the condensation of atmospheric moisture on the cup when cold drinks are served in it.
In addition, the double coating makes the packaging products very sturdy and maintains their shape even when used to serve cold food or beverages.
Moderate MVTR Permeability
MVTR or moisture vapor transfer rate is the property that tells how good your packaging material is at keeping dry products dry and moist products moist against environmental differences.
Any good packaging material is expected to keep the products in their original state, whether dry or wet, regardless of environmental conditions.
PE coating achieves intermediate results in this case as it provides average to good MVTR permeability.
Good Grease/Oil Resistance
When you pack your favorite fries at a restaurant, the PE-coated packaging will ensure that your hands remain oil and grease-free.
The PE coating does not let the oil or grease permeate through the paper packaging and keeps the outer surface of the packaging dry and oil-free.
Good Heat-seal Ability
One of the best features of PE coating paper is that it can be sealed shut using heat.
Since the paper packaging is lined with plastic, the heat sealing machine can remelt the plastic and seal the package shut.
This will help you keep the contents inside the paper package hot or cold as they were meant to be.
Relative Chemical Inertness
Even though PE is a chemical product, it is relatively inert to other chemicals and materials.
This makes PE coating paper very easy to use in different industries. Chemical inertness is one of the contributing factors to the versatility of PE coating
Flexible
Paper by itself is flexible to a certain extent, but it tends to tear if you crease, groove, and fold it repeatedly.
That lack of sturdiness can be fixed when the paper is coated with polyethylene.
PE coating by itself is very stretchable and flexible. When force is applied to polyethylene, it stretches instead of breaking.
So, paper coated with PE also gains the good properties of polyethylene, making the product very flexible and sturdy
Highly Permeable To Oxygen Gases
Oxygen may be the giver of life, but oxygen promotes bacteria and other microorganism growth that will spoil any food or other items inside the packaging when it comes to packaging.
PE coating is limited in this department because it is highly permeable to oxygen gases, making it not a suitable packaging material with a long-term shelf life.
Is PE Coated Paper Biodegradable?
No, PE coated paper is not biodegradable. It can be recycled, but that is a long and slightly expensive process compared to other products.
However, new coating solutions have been developed, such as PLA liner and water-based barrier coating, which are 100% biodegradable and sourced naturally instead of being sourced from crude oil and natural gas.
Is PE Coating Paper Microwavable?
No, PE coating paper is not microwavable because PE has a low-temperature resistance performance of around 80-100 Centigrade.
If that temperature barrier is reached or crossed, PE can expel poisonous substances such as PFAs. So, that’s why most PE-coated paper products are not microwavable.
So, that is all the information you need to know about PE coating paper to prove why it is the industry leader in paper coating.
Sure, PE has its disadvantages and problems regarding biodegradability, but it is still one of the most cost-effective paper coating solutions available on the market.
It also has a tried and tested track record of providing excellent paper coating service. So, if you are interested and wondering about PE-coated paper price, you should know that it will be less than the most equally effective paper coating solutions in the market.
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Read More »Troubleshooting Common Slitting and Cutting Problems for flexible packaging manufactures
Blades are needed for converting blown film into desired dimensions. This text focuses on common problems and their solutions when cutting or slitting blown film. It will go through 13 common problems for flexible packaging manufacturers. It also describes the most common parameter adjustments operators can do to avoid problems and optimize production.
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The main reasons for slitting and cutting problems are blunt or improperly sharpened knives. Sharper knives provide greater efficiency when cutting any material. Sharper knives produce a cleaner cut without tearing, resulting in greater efficiency, higher throughput, and a better quality end product.
About problems encountered when slitting and converting blown film containing many additives and mineral-based fillers, and how to solve them, you can read in a dedicated article"7 Challenges in Slitting Blown Film with Filler Masterbatches".
Content:
Interrupted slits are extremely important to avoid when producing blown film and foil. Interrupted cuts are usually caused by damaged blades or an incorrect cutting angle. Bottom knife runout or low lateral contact pressure can also result in interrupted slits. Professional blade sharpening is a repetitive process in which quantity and quality go hand in hand. A larger quantity usually leads to better quality. So buy and resharpen your machine blades in batches, and you're more likely to get more consistent quality.
Inferior cutting edge quality can be the result of poor blade quality or improper settings during the cutting process. A blunt or burred blade alternately a blade with poor grinding will result in inferior cutting edges. Other reasons can be offset knives, blade vibrations, or wrong web guidance. Too high lateral contact pressure or the wrong shear angle are also reasons for worsened cutting edges.
Therefore, if you notice a deterioration in the quality of the cutting edge, start by replacing the blades. If the quality of the cutting edge has improved, you can choose a blade with better characteristics (e.g. with a different coating or made of a different material). If blade vibration is the cause, try using a slightly thicker blade or knife. Changing the blade from 0.13mm to 0.20mm can significantly affect blade vibration, although in general you should try to use as thin a blade as possible. Vibrations alter the cutting angle. Blade and equipment vibrations should therefore be avoided.
Steel is a relatively soft material that will not stand long-term abrasive wear. Poor steel gives short durability as the blade edge will wear down quickly. Many factors influence abrasive wear and how blade material is removed. Fragments of the blade edge are separated, generating small fractures in the blade edge. Similar to grinding the film grit will wear down the blade edge. The more abrasive additives in the film, the faster the blade will be worn down.
Hard metal and ceramics are much harder than steel and can be used to protect the edge or make blades that withstand abrasive wear much better than steel. A Sollex customer converting process with a film containing white chalk showed how durable hard metal and ceramic coatings could be. A normal razor blade lasted 20 minutes. The same blade with Sollex ceramic coating lasted 2 weeks. Different web materials require different blades. However, it is possible to have blades with high performance and long durability.
Material changes give different abrasive wear on the blade. Different films wear the blade down in different ways. A laminated film with PP, PE, PET and additives such as Titan (TiN) wears down almost all blades. One Sollex customer had a problem with this film until he found 5V. A top-performing, hard metal, long-lasting slitter blade that endures abrasive wear. There is a correct blade for each purpose.
Other reasons for short blade service can be too high lateral contact force or too large shear angle. Equipment vibrations can ruin the blade and be the root cause for short blade service.
For top and bottom knives, a too-large knife overlap or outrunning bottom knives will severely diminish the blade service lifetime. In addition, it is important that the axial speeds of the top knives to bottom knives are the same as the material web. Finally incorrect regrinded knives will also play games with the cutting quality and the knife lifetime. Read more about this topic in Slitting Methods to Cut Web Material: Shear, Crush and Razor Slitting blog post.
High-performance industrial razor blades provide a cleaner cut of web materials compared to top and bottom blades. Cleaner cuts reduce the presence of dust particles between film layers, resulting in an end product with higher quality.
Razor blades provide inferior slitting quality in blown plastic film production. Dust is the most unpleasant production factor for film manufacturers. Even if you use a razor blade, you can get dust. Each film is unique and requires a precise blade for cutting. For example, white film cut with an ordinary razor blade can produce dust, as demonstrated in this picture.
The picture shows a white film being cut at 250 m/min. But the same film being slit with a Sollex-K blade (ceramic-coated blade) produces almost no dust and can run in 350 m/min. We have found that dust generation with razor blades is related to blade thickness, topography, and blade edge friction.
When using circular top and bottom knives, blunt top knives or improperly sharpened top knives are most likely to cause dust formation. Parameters such as too much knife overlap or cutting angle should also be considered when minimizing dust. Finally, unstable blade guidance is a common factor in dust formation during cutting. Make sure that the blade guides are fixed and sturdy so that no dust is generated.
It is a relatively common problem for film manufacturers to tear film instead of cutting or slitting. Torn film gets useless, so avoiding tears is imperative for flexible packaging manufacturers. The material web line usually tears off at the point of intersection.
We find several reasons for tearing. For razor blades, tearing appears when the topography of the blade edge affects the web. A blade optimized for slitting film with white chalk may tear a thin, stretched film at high speed. Counterwise, a blade made for stretch film may be useless for slitting film containing white additives.
For top and bottom knives when shear slitting, teared film occurs when there is a knife offset for the top and bottom knives, which means they are wrongly adjusted for a tangential cut. An alternative is that the knife overlap is too large. Not strictly related to the slitting process but still a very common cause for tears is incorrect web guidance or that the exhaust waste strip needs to be adjusted.
One possible serious consequence of material tear can be the lack of roll separation. Basically, the material web does not separate because the tear glues the film back together due to electrostatic attraction.
Other reasons for the non-separation of the rolls could be that the listing tools are damaged or the web tension is too high. As always, in order to correctly separate rolls, the web should be guided or supported at the point of intersection. Material jamming in front of the slitting zone and roll separation can be the result of too slow feed of the bottom blade.
Another consequence of tearing could be an uneven roll edge. Winding layer after layer of rough roll edge looks like absurd annual rings from a cut tree rather than a desired CD-disc. Again, blade edge friction and material type play an important role. Therefore, it is critical to have the right blades for the specific application. Annual rings when slitting stretch plastic film can also be created by inconsistent material tension or a loose shaft.
A rough edge of the roll, a non-straight edge, or the more common name for annual growth rings creates electrostatic stress between rolls of film. Placed together on the pallet, these tensions can act like glue, making it impossible for your customer to separate the rolls. As a result, your customer may complain about the quality or find the shipment useless.
Non-straight section lines can occur when using top and bottom knives. Non-straight section lines are usually the result of loose knives or a worn-out bottom knife. Make sure the cutting equipment is properly fixed and the bottom knives are resharpened or new.
"Angel hairs" is a clear sign that the cutting process is not working properly. Look for vibrations and monitor the operation of the top and bottom knives. It may be time to replace or regrind. If this scenario happens often, you may want to consider a different blade design to make it work.
Optimized industrial razor blades produce clean cuts. Poor blades can cause corrugations on the material cut edge. When the web is winded, corrugations upon corrugations give a raised roll edge. This builds up the material edge. Edge-built-up films are often considered unusable as they possess large difficulties to unwind.
If you are experiencing edge buildup up when using top and bottom knives, it might make sense to try using razor blades instead. Since the top and bottom blades work at high cutting speeds, they produce poor-quality cuts. The cut with a razor blade will be cleaner.
If industrial razor blades create a buildup of edges on the web of material, it is recommended that you first check the direction of the web and make sure that the foil is slightly stretched against the cutting blade. Also, make sure that there is constant material tension and that the shafts are fixed. After checking the settings of the slitting process, the next step is to test the blades of different thicknesses. A general recommendation is to try thinner and thicker blades to look for improvements or deteriorations. For example, if you are using a 0.20mm razor blade, test how a 0.13mm or 0.30mm blade will affect your cutting and edge build-up. So, for thin stretch film at high speed, check 2-013-Z, 2-020-Z or 2-030-Z. For film containing white additives such as chalk, try 2-013-K, 2-020-K or 2-030-K. For thick multilayer films containing layers of Polypropylene (PP), Polyamide, and Elastomers (TPE) we have found that our blade 2-020-V works well to avoid Edge build-ups. Like-wise when it comes to adding colors 2-020-X works wells when slitting in printed areas and still minimizing edge build-ups-
Check which solution gives the lowest edge buildup - iterate from there.
Burrs and dents are the worst proof of insufficient blade quality. Burrs and dents show that the blade manufacturing process is malfunctioning. Alternatively, the batch is useless. Burr is blade material (most likely steel but can be ceramics or hard metal) that has not been removed by the last and finest grinding of the blade. Dents are small cracks in the blade that imply that the blade has been damaged. With burrs and dents on the blade edge, it's time to change blades.
There is a very effective way to check blades for burrs and dents. Take two blades and slowly slide them edge to edge. You will feel burrs and dents directly. An alternative is to use light on the edge to see spatial differences.
Blunt slitting tools can cause the material web to penetrate between the top and bottom knives. Regrinding is therefore a serious and professional craft. For high-performance circular knives, you need a really good regrind and someone you trust. The optimal way is to let your original manufacturer regrind. Then you will have the most similar re-grinding as the original knife. When regrinding you will get new angles or shorter diameters. So blade design and performance will change. Wrong or bad grinding / regrinding can result in too low lateral control pressure. In addition, improper regrinding can result in chips, dents, and burrs on the cutting edge.
Bad handling of sharp knives is probably just as tough on blades as when they are worn out. Therefore, packaging and storage are extremely important for long blade durability. Depending on the design, size, and quantity, there are many different packaging options for knives and blades. With proper handling and packaging, blades can be stored for a very long time.
A quality blade packaging should:
The steel will all corrode. Since stainless steel is resistant to rust, it can still corrode over time. A blade has to be lubricated to prevent corrosion. Wrapping it in protective paper is the second step. Utilizing a vacuum is a third tactic to prevent oxygen from reaching the steel. Because cardboard absorbs moisture, it is the recommended material for second packing. Lastly, the inside is shielded by a wooden exterior box.
Maintain a regulated, low-humidity atmosphere in any spaces where blades are kept or utilized. Relative humidity should ideally be less than 50%. It is recommended to keep the temperature between 20 and 22°C (68 and 72°F).
Industrial blades from Sollex are always supplied well-oiled and vacuum-sealed.
You may learn about how to keep industrial knives and blades from corroding here.
Learn more about industrial knife materials in an article Overview of Materials for Industrial Machine Knives.
Sollex is your industrial blade manufacturer and supplier. We are based in Sweden, Europe and work solely with knives and blades. We have a wide product range with different industrial razor blades such as slitter blades, straight three hole blades, round 3 hole slitter blades, injector blades, industrial double edge razor blades. In addition, we keep a lot of machine knives in stock.
Try Sollex Zero Friction blades: Type Z for stretched thin films without additives. For film with additives, such as white pigments, try Type K blades. A basic TiN coating blade type T can be used in a wide selection of applications.
PP with additives (for instance, such as calcium carbonate, which makes it similar to rubber) is really tough on the blade. Cutting such film requires extreme performance and durability. Sollex V quality, such as 5V, can work in extreme cases. Normal PP without additives should work with Sollex K and Z blades. C blades stay sharper even longer as they are self-grinding. But the C quality is also a bit fragile. If you require something between V and K, Sollex X quality is a good choice.
Read our guide about product qualities and coatings here.
Our industrial-type razor blades are made of high quality stainless steel with different coatings on the edge or side of the blades. Sollex blades are available in solid tungsten carbide or ceramics. If you do not find the razor blade you are looking for, Sollex are able to manufacture industrial razor blades according to your drawing.
Download PDF with Sollex Slitter Blades for Plastic Industry
Contact Sollex and we'll be happy to help you with samples so you can test them on your production line. You are welcome to contact us at +-15 75-00 or at if you have any questions regarding our industrial razor blades.
About the author Johan Falk is an expert on knives and blades and the CEO of Sollex. You can contact him directly on: 708 744 786 or . For general sales questions drop an to or call us on 35 15 75 00
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Sources:
1. Wikipedia
2. Dienes https://www.dienes.de/en/, Accessed the 2 January
3. Fortis https://www.fortisblades.com/, Accessed the 2 January
4. ROBERT HARRISON, WITTMANN INC., Eliminate Dust, Fines and Longs For Better Regrind Quality, https://www.ptonline.com/articles/eliminate-dust-fines-and-longs-for-better-regrind-quality, Accessed the 2 January
5. What is a burr? https://scienceofsharp.com//01/13/what-is-a-burr-part-2/, Accessed the 2 January
6. Source (for all SEM pictures here) from the scienceofsharp web page https://scienceofsharp.com/, Accessed the 2 January
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