LOGOJET Understanding UV Printing Adhesion User Guide

: August 8, 2024
: LOGOJET

Table of Contents

Understanding UV Printing Adhesion
Specifications
Product Usage Instructions
Surface Preparation
Choosing the Right Ink
Primers and Adhesion Promoters
Surface Treatments
Mechanical Abrasion
Proper Curing
- FAQ
Q: How do I know which primer or adhesion promoter is suitable
Q: Can I use any UV-curable ink for all substrates?

Understanding UV Printing Adhesion

“`html

Specifications

Printing Technology: UV Printing
Substrates: Glass, Metal, Plastic, and more
Ink Chemistry: UV-curable inks designed for specific
substrates

Product Usage Instructions

Surface Preparation

Properly clean the substrate surface using lint-free wipes to
remove contaminants like dust, oils, and grease that can affect
adhesion. Ensure the surface is free from static to optimize ink
bonding.

Choosing the Right Ink

Select the appropriate UV-curable ink formulated for the
specific substrate to ensure optimal adhesion. Consider the
material’s flexibility or rigidity needs when choosing the ink.

Primers and Adhesion Promoters

Follow manufacturers’ application guidelines for primers and
adhesion promoters tailored to different substrates. Pay attention
to storage instructions and expiry dates for maximum
effectiveness.

Surface Treatments

Flame Treating:
– Surface Cleaning: Remove contaminants
– Surface Activation: Enhance ink receptivity
– Mold Release Removal: Improve adhesion
– DIY Feasibility: Suitable for various applications

Corona and Plasma Treatments:
– Surface Activation: Modify at a molecular level
– Industrial Use: Often in large-scale production
– DIY Feasibility: Not recommended due to complexity

Mechanical Abrasion

Lightly sand or abrade the surface to create a rough texture for
better ink adhesion, especially effective for metals and hard
plastics.

Proper Curing

Maintain a controlled printing environment with optimal
temperature, humidity, and dust levels to ensure consistent
adhesion quality.

FAQ

Q: How do I know which primer or adhesion promoter is suitable

for my substrate?

A: Refer to the manufacturers’ recommendations for primers and
adhesion promoters designed for specific substrates. Choose based
on the material you are printing on.

Q: Can I use any UV-curable ink for all substrates?

A: It is essential to select UV-curable inks formulated for the
specific substrate you are printing on to achieve the best adhesion
and print quality.

“`

Understanding UV Printing Adhesion: Concepts, Tools, and Tricks
UV printing technology has revolutionized the printing industry with its ability to print on various substrates, including glass, metal, plastic, and more. How-
ever, one of the critical factors determining the quality and durability of UV prints is adhesion. Let’s dive into the concepts of UV printing adhesion and
explore tools and tricks to overcome adhesion challenges.
What is UV Printing Adhesion?
Adhesion in UV printing refers to the ability of the UV-curable ink to stick to the substrate. Unlike other inkjet technologies, UV ink does not require a porous substrate or a coating for proper adhesion. UV ink is cured or solidified on the substrate surface through exposure to UV lamps during the printing process. However, without proper adhesion, the cured ink may not be durable enough for the intended application. Think of UV ink adhesion the same as a paint project at home. Without proper cleaning and surface preparation, you will likely have poor or undesired results. Ensuring strong adhesion is essential for producing durable and high-quality prints.
337.330.8471 | Sales@LogoJET.com | LogoJET.com

Key Concepts in UV Printing Adhesion
Surface Energy
The substrate’s surface energy significantly impacts adhesion. High surface energy materials, like ABS and Polycarbonate plastics, and products coated with a polyurethane or resin-like metals, typically provide better adhesion for UV inks. Conversely, low surface energy materials, such as certain Polyethylene and polypropylene plastics, glass, and raw metals, can pose adhesion challenges if no pretreatment is applied. Porous substrates, such as wood or paper-based medias, are generally not affected by surface energy. Having a dyne level kit to test surface energy (shown in photo) can be ideal, as UV digital inks generally perform best in the 40-50 dyne level range.
Ink Chemistry
The formulation of UV-curable inks affects their adhesion properties. Inks are designed with specific chemistries to adhere to different substrates, while providing the right flexibility or rigid needs. Choosing the right ink for the material is crucial for achieving optimal adhesion.
Surface Preparation
Properly preparing the substrate surface enhances adhesion. This involves cleaning the surface to remove contaminants like dust, oils, grease and in some cases even static, which can hinder ink bonding and print quality. Proper materials like clean, lint-free wipes will help prepare the surface without scratching sensitive materials.

Tools and Tricks to Overcome Adhesion Challenges
Primers and Adhesion Promoters
Applying an adhesion promoter can significantly improve ink adhesion, especially on difficult substrates like plastics. These products create a bondable surface, enhancing the ink’s ability to stick. This process is best applied manually by applying the liquid pretreatment to a lint-free microfiber cloth and applying to printable area before printing. This process is fast and dries within a few seconds and in some cases can be applied in advance up to 24 hours before printing if the applied area is not handled with fingerprints.
Always be sure to follow the manufacturers’ application suggestions and guidelines. There is no single best adhesion promoter, as they are each designed for specific substrates and applications. Also, pay close attention to storing instructions and expiry dates, as some have a 6-12 month shelf life.
Surface Treatments
Flame treating, corona, and plasma treatments are all methods used to prepare surfaces for better adhesion of UV digital ink. Here’s how they compare:
Flame Treating
Surface Cleaning: Removes dust, oils, and contaminants. Surface Activation: Oxidizes the surface, enhancing ink receptivity. Mold Release Removal: Eliminates mold release agents for better adhesion. DIY Feasibility: Can be done in-house with appropriate equipment, making it accessible for various applications.

Corona and Plasma Treatments
Application: Typically applied during the manufacturing process. Surface Activation: Modify the surface at a molecular level to improve adhesion. Industrial Use: Often used in large-scale production; standalone devices can be integrated into workflows for continuous treatment. DIY Feasibility: Generally not a DIY option due to the complexity and cost of the equipment.
In summary, while corona and plasma treatments are more industrial and integrated into manufacturing, flame treating offers a flexible and accessible method for improving print adhesion in a variety of settings, including those with mold release coatings.
Mechanical Abrasion
Lightly sanding or abrading the surface can create a rough texture, providing more surface area for the ink to adhere to. This method is particularly effective for metals and hard plastics.
Proper Curing
Proper curing of UV ink is crucial for ensuring strong adhesion and durable prints. Insufficient curing can lead to poor adhesion and print durability issues. Adjusting the curing parameters, such as UV lamp intensity and exposure time, based on print speeds, can help achieve optimal results. Regular maintenance of the lamps, including cleaning the UV lamp glass, is essential for proper UV light emission. Additionally, maintaining the correct distance between the UV lamp and the printing surface is important. UV printers are calibrated to have the UV curing lamps at an optimal distance from the product for proper curing. Increasing that distance can result in improper curing, leading to poor adhesion and print durability issues.
Environmental Control
Maintaining a controlled printing environment helps in achieving consistent adhesion. Factors like temperature, humidity, and dust levels can impact the printing process and adhesion quality.

Testing and Quality Control
Regularly testing the adhesion of prints ensures that any issues are detected early. This is highly recommended considering materials can change across various batches and printing with expired inks can also impact durability. Traditional nail scratch, cross-hatch adhesion tests, tape tests, and pull-off tests are commonly used methods to evaluate adhesion strength.
Consideration of Substrate and Application
Understanding the intended use of the printed object is crucial. For example, printed artwork displayed in a museum typically isn’t exposed to abrasion, moisture, or extreme conditions, making most substrates suitable. On the other hand, a printed mug, which undergoes frequent handling and exposure to wear and tear, demands the best possible adhesion. Offering customers various materials with different adhesion levels (poor, better, best) can be beneficial, especially if the item is for novelty or daily use. Additionally, some materials may have hydrophobic coatings applied during manufacturing, designed to repel liquids and hinder ink adhesion. In such cases, the aforementioned methods may have little or no effect on improving ink adhesion.
Conclusion
Achieving strong adhesion in UV printing is a combination of selecting the right materials, preparing the substrate, and fine-tuning the printing process. By understanding the concepts of UV printer adhesion and employing the tools and tricks discussed, you can overcome adhesion challenges and ensure high-quality, durable prints.

Matrix of Materials and Pretreatment Requirements

By applying the appropriate pretreatment methods, you can ensure high-quality, durable prints on a wide range of substrates. Understanding and implementing these techniques will help overcome adhesion challenges on your product application.

The matrix below shows options for increasing adhesion when required. These methods should not be used together. For example, when applying corona treatment, additional pretreatment is not necessary.

MATERIAL
Glass for display purposes Glass for dish wash applications Metal (example: aluminum, stainless steel) uncoated Metal (example: aluminum, stainless steel) coated Aluminum Composite Material (DiBond, MaxMetal, AluPoly) Injection Molded Plastics Polypropylene, Polyethylene, Nylon Corrugated Polypropylene for Signage (corona treated i.e. Coroplast) Plastic ABS, Polycarbonate PET (polyethylene terephthalate) HDPE (high density polypropylene) Nylon Foam Board PVC Kydek Tyvek Adhesive Vinyl Banner Material Wood Ceramic – Glazed Ceramic – Non-Glazed Acrylic – cast Acrylic – extruded Laser engravable plastic stock* Laser engravable UV coated plastic stock Paper/Cardboard Fabrics Genuine Leather Synthetic Leather Polished Stone (example: marble, granite)
Porous Unfinished Stone (tumbled travertine, slate, botticino) Rubber Soft Rubber Sublimation blank materials (polyester coated)

Pre-Treatment Recommended Yes Yes Yes
No
No
Yes
No
No No Yes Yes No Yes No No No No No Yes No No Yes Yes No No No No Yes Yes No
Yes Yes Yes

PreTreatment x x
x
x x
x x x
x x x x x

Flame x x
x

Corona or Pyrosil Mechanical

Plasma

Abrasion

x x

Always test the material, as not every substrate is obvious and may contain blends, coatings, mold releases, or other factors affecting adhesion. *no pretreatment required for engravable stock developed and designed for printing with UV LED cured inks. (Example: Digimark,Trotec Digital Print Series, etc)
www.logojet.com

Pretreatment Methods
MANUAL HAND APPLICATION TOOLS Pretreatment: a liquid that is manually applied to a microfiber cloth before printing. Improves UV bond to surface.
Isopropyl Alcohol: commonly used to clean most materials before printing to remove contaminants, in some cases increase adhesion and prepare surface.
Flame Treatment: Alters the surface of plastics like polyethylene to improve ink bonding.
Mechanical Abrasion: Roughens the surface, increasing the area for ink to adhere, especially useful for metals.
Pyrosil Treatment: Especially effective for glass, creating a durable, dishwasher-proof bond.
INDUSTRIAL APPLICATION TOOLS Plasma Treatment: Enhances surface energy and cleans the substrate, improving adhesion for various materials. Corona Treatment: Increases surface energy, particularly useful for lowenergy plastics. *typically can be applied during product manufacturing process
www.logojet.com

Essential Pretreatment Tools for Your Printing Mix

TOOL Adhesion Promoter

PURPOSE Low odor, general all purpose

RESOURCES www.logojet.com

Bohle Metal Adhesion Promoter
Marabu P2 Poly adhesion Promoter Marabu P4 Stainless Steel Promoter Supply 55 (AP2155)

Best for metals and other materials that have sensitive coatings or other promoters ruins the surface, the Bohle is less aggressive Best for plastics, especially PP/PE

www.logojet.com www.logojet.com

Best for metals

www.logojet.com

Best for plastics, especially PP/PE www.supply55.com

Supply 55 (AP3155) LogoJET

General all purpose

www.supply55.com

RedHot Adhesion Promoter

General all purpose

www.mimakiinkjet.com

Dyne Level Test Kit
Pyrosil Handheld Kit for Flame Treatment Corona Treatment Equipment
Plasma Treatment Equipment
Flame Treatment Tools
Mechanical Abrasion Tools (sand paper or scouring pad) UV Curing system

To test surface energy
Best to treat glass that is intended for dishwash purposes For increasing surface energy of plastics For increasing cleaning and activation For materials like polyethylene
For creating texture on metals and hard plastics To ensure proper curing of UV inks

Amazon Accu Dyne Test Full Set www.chemical-concepts.com
www.tantec.com
www.tantec.com
Handheld Local Hardware Store Automatic/Professional Series Local Hardware Store
Built into UV printers

Isopropyl alcohol (91 or 99%)

Used to wipe materials of dust, Local Hardware Store debris, fingerprints before printing

To summarize, using the correct pretreatment methods ensures superior adhesion and durability in UV printing. Scan the QR code here to read the full blog article for more details or contact LogoJET to speak with a Technical Specialist about your project.