How to prepare LSE substrates by using Corona Treatment

2. Some doubts about Corona Treatment
By corona treating on a HDPE surface, how much will the surface tension/energy increase?
It's the same as PE . In Pe you have 2 varieties like LDPE or HDPE. The Surface
Tension will increase from 33 to approx. 45 or 46 dynes/Cm2
Once corona is treated on a HDPE sheet, within how much time do we have to apply the
HMA? How will it be different in summer and winter?
Generally the Corona treatment is good enough for 3 to 4 months. Later on it starts feeding
on its own.
Will the tensile strength of the HDPE sheet be affected if corona is treated?
No, the Corona Treatment dont alter any Physical property atall.

3. Some doubts about Corona Treatment
Are fumes emitted harmful for us? What are the best safety practices while dealing with
corona treatment on HDPE sheets?
There are no fumes emitted while Corona Treatment. However the Ozone gas is emitted
and it has a strong odor. Generally the Ozone emitted is exhausted out of the shop floor
with a suitable ducting made of HDPE or PVC or Steel Pipe . A Exhaust fan is essential for
the same.
Best practice of choosing HMA for HDPE sheets?
The choice of HMA depends on the required peel strength, shear and Tack Properties.
Generally HDPE can not be coated by Direct coating Method while coating HMPSA or SB
PSA , however WB PSA can be directly coated. In case if you wish to coat HMPSA on
HDPE film or sheet, then Transfer coating method is the most popular one. That is coating
HMPSA on silicone coated paper or Si coated PET film and then Laminating the same with
HDPE film , corona treated. later on you may remove the si liner and produce self wound
HDPE tape. However prior to rewinding the HDPE film needs to be coated with a Non
Silicone coating , in order to have smooth unwinding of HDPE Tape.

4. Which is the best adhesive that can be used for a corrugated sheet manufacturing process ( i
just heard starch is used, but no in-depth knowledge)?
Starch is still used as an adhesive for corrugated sheets or box manufacturing , However
starch based adhesive are hygroscopic in nature and hence they absorb moisture ,
especially in the rainy season hence syn adhesive based on PVA are mostly prefered. I have
a Lecture ready on the same.
You may find a URL pasted below to now more about Corrugation adhesives.
https://www.slideshare.net/ashrikant58/pk130-pkppt-on-adh-4-corrugated

5. Specifying the right Corona Treater when Buying from an OEM
When purchasing a new line or press from an OEM, the specifications on the corona
treater is often a secondary consideration. However properly specifying the corona treater
pays massive dividends down the road. Let’s look at some tips to keep in mind when
working with an OEM on a new line that features a corona treater.
First, its important to recognize that corona treaters are custom pieces of equipment. This
is a great advantage for companies who think about how they are going to initially use the
corona treater and how they might need to use it in the future. It’s not uncommon for two
companies purchasing the same OEM press for the same application to specify a different
corona treater configuration for the same application. Likewise it is possible that two
different OEMS might specify slightly different corona treater specifications for the same
application.

6. How do these Specifications Alter the Corona Treater?
These are the types of details which will often come out in direct conversations with a
corona treater supplier. By sharing additional information with your OEM the
specification for the corona treater dramatically changes:
Needing to treat conductive materials eliminates metal electrode & covered roll
systems
More difficult to treat films, increased additives and higher line speeds require higher
watt densities
Higher watt densities may impact the power supply, electrode configuration, ground
roll sizing and exhaust requirements
In the scenarios above, ABC company paid a little less for their corona treater, but they
also sacrificed flexibility to accommodate any potential future changes in their
operations. If their line remains dedicated to running the same exact application,
they’ve made a wise choice and saved themselves a few dollars. Company XYZ
invested a little more upfront, but also positioned themselves to accommodate a number
of future scenarios by incorporating

7. Get your Application and Integration Right the First Time
You’ll find Enercon equipment integrated on printing, coating, laminating and
extrusion lines with every major OEM in the world. Enercon works very closely with
all OEMS to ensure they also recognize critical variables that can impact corona treater
selection. The important thing to remember is a corona treater is a custom piece of
equipment. And defining the application variables at the beginning of the project will
avoid application issues down the road which ultimately can lead to spending a lot
more to upgrade in the field.
When it comes to integrating with OEM equipment Enercon has a team of engineers
dedicated to managing all aspects of these OEM projects to ensure all objectives from
both the OEM and end user are satisfied. Seamless mechanical, electrical and control
integration ensures a smooth start-up and operation. Enercon’s experience with our
partner OEMS also adds value to new treaters for existing OEM installations. Our
engineering team will save you time and money by offering systems that are custom
designed to fit mechanically and electrically to meet your project’s unique
specifications.

8. Improve Print Quality & Productivity by
Controlling
Substrate Surface Energy
Poor ink adhesion affects print quality, creates
downtime, and leads to lost customers. In many
cases the cause is rooted in complications from
the substrate surface. The good news is that
surface variables can be eliminated with the
proper use of a corona treater.
A common misunderstanding is that pretreated
films eliminate the need for additional in-line
treatment. This technical paper examines the
factors that accelerate dyne decay and provides
a solution to overcome them.

9. Corona Treatment For Extruded Film (Cast & Blown Film)
Most cast and blown film extruding applications are best served with a covered roll
surface treater. Enercon offers two types of covered roll systems for extruding
applications. Our original covered roll system is designed to meet the needs of the
high performance lines and our new blown film station capably handles the
requirements of lower speed applications.
Covered roll systems can only treat non-conductive materials. You should always
consult with an Enercon Application Expert to determine the best system for your
application.
Enercon’s line of covered roll treaters support all aspects of the extrusion industry.
From wide to ultra-wide applications these systems rely on metal electrodes and a
dielectric covered rolls. They can be configured for treatment over the entire length of
the web or for lane, skip or pattern treatment..

10. Enercon’s patented design combines the advantages of an ozone-safe work area with
the latest benefits of advanced technology. The long-term reliability of the Enercon
design is further enhanced by the unique air-flow which cools the electrodes, pulls a
constant supply of oxygen into the corona, and removes the ozone directly from the
airgap.
Enercon offers two covered roll systems for extruding applications. The Covered Roll
system is capable of handling virtually any extrusion applications including high end
blown film lines. New to the Enercon line-up is AirTreat™ which provides remote
and automatic electrode segment actuation which helps reduce scrap and improve
productivity.

11. Covered Roll System
This system is available in a variety of sizes and configurations to meet the needs of
the extruding industry. Metal electrode options include fixed length stainless steel
tubes and stainless steel segmented electrodes. Segmented electrodes allow for lane
treating. Roll coverings are either made of a removable sleeve, or material that is
vulcanized or coated onto the roll. Ceramic, silicon, epoxy, and hypalon, are some of
the more commonly used coverings. Visit the Covered Roll product page for more
information.
Blown Film System
This compact system was specifically designed for blown film lines with limited
speed requirements. These systems rely on segmented aluminum electrodes and
dielectric roll coverings. Based on application requirements the roll covering may be
made of silicone, ceramic or epoxy. Visit the Blown Film product page.

12. Ultra-Wide Web
Enercon’s Ultra-Wide surface treaters are designed for reliable treatment for lines up
to 10 meters wide. The system’s unique electrode mounting assembly virtually
eliminates electrode warping due to thermal expansion. This assembly ensures
consistent treatment across the entire length of the web. Our Compak 9000 power
supply efficiently handles the power requirements of these ultra-reliable systems. Visit
the Ultra-Wide product page for more information.

13. Corona Treating Frequently Asked Questions (FAQ)
Wonder how corona treating works and what it really does to surface of your substrate?
We've answered these questions and a few others that we are commonly asked.
Can all types of substrates be treated on either a bare roll, covered roll, or universal
roll system?
No. Covered roll system can only treat non-conductive substrates. Bare roll or universal
roll systems can treat both conductive and non conductive substrates.
What is the difference between a covered roll treater, bare roll treater and a
universal roll treater?
The difference between the two systems relates to where the insulator is in the treating
station. In a covered roll station the roll is insulated with some type of dielectric material
and the electrode is bare metal. In a bare roll system the roll has no insulation, but the
electrode is insulated. In a universal roll station both the ground roll and the electrode are
insulated.

14. What does corona treating do to the surface of converting films?
Corona treating forms low-molecular-weight (LMWOM) on film surface; oxidizes film
surface; and forms positive and negative sites by adding and deleting electrons.
What is corona?
Corona is ionized air created by discharging high frequency high voltage energy across a
metal or insulated electrode. This electrode is positioned over a grounded roll. The space
between the electrode and the roll is typically .060". It is in this air gap that corona is
generated.
What is dynes/cm^2?
Dyne level is a unit of measurement used to determine the surface energy of (in our
industry) the surface of a films or foils. Most polyolefin films have low dyne levels some
where between the high twenties to low thirties. In order to be able to convert these films,
the surface tension will need to be between the high thirties to mid forties. Corona
treating is used to accomplish this increase in dyne level. How does your application
stack up? Visit our recommended treatment range matrix.

15. Some video’s
https://youtu.be/sh6cESlhDLM
https://youtu.be/1Yoq-1Jjr68
https://youtu.be/xQui0-QYbBk

16. How Bump Corona Treating Improves Laminating, Coating & Printing
Whose responsibility is it to make sure a film is ready to be converted? Film supplier or
Converter? Depending on what part of the world you are in this question can spark an
inspired debate.
Both the film supplier and the converter are in business to make money. When printing,
coating & laminating applications go wrong it’s a financial hit in either scrap material or
in lost customers. So what’s a converter to do?
The tendency in emerging markets is for converters to reject film at the receiving door if
it fails a dyne level test. And this is somewhat understandable. Many emerging market
converters have no way of successfully converting film with low dyne levels. They
expect their supplier to provide ready to convert film.

17. What mature market converters have come to recognize is that there are a number of
factors outside the film supplier’s control and it is in their own best interest to take
control of their process by adding “bump treating” into their standard process.
“Bump treating” refers to the installation of corona treater(s) on the converting line
immediately prior to the application of inks, coatings and laminations. This “fresh”
corona treatment provides converters with more control of their process. It enables them
to overcome unexpected fluctuations in incoming film dyne levels and increases their
operating window.
This article will review the factors that have driven leading converters in mature
markets to take control of their processes by adopting “bump treating” as a standard best
practice.

18. From Resin to Converted Product
To understand the differing views on this concept we need to follow the journey of a
film from resin to finished product.
The whole concept behind surface treatment is to improve wettability and promote
adhesion. When most films are extruded from resin their surfaces are non-porous and
chemically inert with very low surface energy. Film extruders will corona treat their
freshly extruded films to increase their surface energy. In fact, film’s that are not corona
treated at the time of extrusion may never be receptive to future corona treatment.
Surface energy is commonly measured in units of measure called dynes. 1 dyne equals a
centimeter-gram-second unit of force. Most converters will have a target dyne level
range that works well for their specific process. While dyne levels do not guarantee
adhesion, generally speaking higher dyne levels produce better adhesion results than
lower dyne levels.

19. Why Dyne Levels Decay
The increase in a film’s dyne level is not permanent. In fact, dyne
level decay and surface contamination are for the most part, out of the
film extruder’s control once the roll of film leaves their facility. Some
of the reasons for this include: Additives: additives are included in a
film extrusion recipe for a variety of reasons such as enabling better
film handling. When a film is freshly corona treated organic and
inorganic contaminants are removed from the surface layer which
actives the surface and increases its surface energy. Over time
additives will migrate to the surface of the film which will diminish
the effects of the corona treatment.
Contamination: handling of the film or exposure to dust, debris or
oils after corona treating can impart contaminants on the film’s surface
Environment: high levels of humidity are known to accelerate dyne
level decay
The increase in a film’s
dyne level is not
permanent. There are
several variables that can
effect the decay of corona
treatment.

20. Environment: high levels of humidity are known to accelerate dyne level decay
Natural decay: even without additives, external contamination, or environmental
factors dyne levels will decay over time. The precise level of decay will vary based on
many factors including the specific substrate and original level of treatment. Under
normal circumstances dynes levels will decay and eventually level off.
This should provide you with a good understanding of some of the reasons dyne levels
will decay at a rate that is often out of control of the film supplier.
Potential pitfalls of dyne level readings?
As a matter of best practices most converters will spot check the incoming dyne level of
films prior to converting. This is a recommended quality control procedure, but caution
should be taken when interpreting the results.

21. Consistency: does your operation have a dyne level test that is consistent and
repeatable? The most accurate results will come from a Meyer rod draw down test.
Some companies use a pass/fail test with dyne pens which can be acceptable, but are
subject to a greater variance in results.
Interpretation: is your staff properly trained in interpreting dyne level test results? It’s
not uncommon for two highly trained people to interpret the same dyne level test with a
margin of error of 1-2 dynes. The message here is that a difference of one dyne is not to
be taken too literally.
Results: does your team understand what they are testing? It’s important to note that a
dyne level test only tests one small portion of the film. There’s no guarantee that the
entire roll of film holds the same dyne level. Furthermore dyne level is only an indicator
of a film’s wettability and actual adhesion is dependent on additional variables including
numerous process parameters.

22. Real world examples
Let’s compare two companies, Company ABC who has invested in a corona treater for
converting and Company XYZ has not.
Scenario 1: Film arrives from a supplier with an acceptable dyne level, but is
inventoried for several weeks prior to converting. The dyne level decays over these few
weeks to the point that it cannot be converted in its current state. Company XYZ
struggles with converting the film and ultimately fails to produce saleable product and
making delivery. Meanwhile Company ABC has no problems converting the film as
they “bump treat” it in line with great success.
Scenario 2: Historically the two companies have laminated film on a solventless
laminator without the need for corona treatment. One day a roll of film appears to have
irregular patterns of surface energy throughout the film. Again Company XYZ struggles
with inconsistent results. Meanwhile Company ABC has eliminated the variable of
surface energy and produces high quality products roll after roll.

23. What Industry Experts Say about Bump Treating
An instructor from a flexographic printing program says, “Films are pretreated, but
they're not guaranteed to be perfect when it comes time to print. Treatment degrades
over time so that's one issue you have to contend with. And, even if the film makes the
grade on a dyne test you still have the possibility of additives rising to the surface.
These surface imperfections can result in pinholing and other quality issues. A corona
treater can help eliminate these problems."
A Director of Engineering from a company that offers custom coating sees other
benefits to bump treating, "There's something to be said for a fresh treat. Dyne level
does not always guarantee adhesion. Dyne level is simply a measurement of wetting-
out. We've seen materials with equal dyne levels, one freshly treated and one from
inventory and the freshly treated material consistently provides the better adhesion."

24. While there are some applications that almost always require bump treating, such as
many water based printing processes, you may be surprised to learn that many
converters find benefits from bump treating solvent printing processes. One solvent
printing Operations Manager recently told us, “There's no doubt that our lines with
corona treaters have less delays and downtime. The treaters provide a safety net that
assures surface dyne levels are optimal for printing."
The Key is Taking Control
Education is key to ensuring both the film extruder and converter understand the
relevance of dyne levels, the role of corona treatment and the expectations that they
should have for each other. The film supplier strives to supply pretreated film within a
dyne level range that can be converted. The converter should take responsibility for
converting that film and do their best to eliminate surface energy as a variable by
employing a corona treater to bump treat films prior to converting.