By Olivia Cahoon
Part 1 of 3
Adhesion promoters or primers help ink adhere to uncommon printable materials. Objects used in the manufacture of appliances, medical, and automotive parts, for example, are ideal candidates. Applied either by automated devices or manually, adhesion promoters increase a printed product’s durability and quality. Some are universal, while others are designed for metal, tile, glass, or a specific paper-based material.
Adhesion Promoters
The use of adhesion promoters in the digital printing process enhance ink and coating adhesion on difficult-to-print-to substrates like aluminum, brass, ceramics, glass, granite, metal, and plastic. They may also ensure ink remains on a substrate. Water-based, solvent-based, or UV-curable adhesion promoters provide enhanced durability and expand the variety of printable media.
According to Susie Mendelssohn, sales manager and international marketing manager, INX Digital, in addition to better ink adhesion, adhesion promoters act as a general cleanser prior to printing and reduce static electricity on the surface. Minimizing static electricity also lessens ink drop deflection and the potential for new particles to attract to the substrate during printing.
Mark Six, technical product manager, wide format solutions, The Mosaica Group, recommends adhesion promoters for materials with very low surface tension or low dyne value. Without good adhesion, he says the material will likely crack or flake off when cut, routed, or handled. Adhesion can also effect abrasion resistance and other factors like smudging.
Application Methods
Application of adhesion promoters is done manually or with automated systems, the process used primarily depends on the type of printer available. “An automatic process is more convenient and preferred to a manual one as results are more consistent,” admits Six.
“An automated process typically removes the room for human error, whereas manual application can result in an uneven or spotty application of the product,” agrees Mendelssohn.
Many older print devices don’t offer an inline priming option, so the adhesion promoter needs to be applied by hand. Some objects may feature an uneven surface or strange shape that would be difficult to run through an automated machine requiring the manual application of adhesion promoters, explains Six.
With manual application of liquid adhesion promoters, Mendelssohn says there is the benefit of the substrate being wiped clean at the same time the product is laid down.
When applying by hand, there are several options. Pedro J. Martinez, CEO, Afford Industrial S.L., says manual processes are performed by dampening, spraying, or using a brush application.
Additionally, Michael Pender, president, Supply55, Inc., suggests using a microfiber cloth or a metal spray gun in a paint booth. “We see most customers applying adhesion promoters to the substrate by hand with a microfiber cloth directly before printing.”
Adhesion Volumes
The volume of primer required is dependent on its chemical nature. For inkjet printing, Martinez says a very thin layer, usually five milliliters per square meter, is enough. “The added cost of an adhesion promoter is roughly 0.5 to one dollar, although it depends on the promoter type, application method, and substrate.”
While the amount of product applied varies based on the substrate, testing prior to committing to a full run helps to confirm the required level of primer. “Each substrate performs differently and requires testing before printing to establish the correct workflow,” recommends Pender.
Raising Costs
Adhesion promoters bring an added cost for the printer and in conjunction, the customer. Using an adhesion promoter or primer takes extra time and extra labor.
According to Six, the extra costs and processes required to adhesion promoters should pass along in the end price. Building the added expense into the quote helps to prepare for jobs that require promoters or primers.
Curt Baskin, field marketing manager, Sun Chemical Corporation, believes the price of a project should be raised due to the extra step in the process.
Sticky Solutions
Adhesion promoters offer the ability to print on a wider variety of substrates while enhancing durability and quality. Before using an adhesion promoter or primer, it’s important to know which application method—manual or automatic—will be used. The next part of this series features a roundup of available adhesion promoters.
Click here to read part two of this exclusive online series, Difficult Substrates Solved.
Mar2018, Industrial Print Magazine