Considerations When Printing and Marking Fluoropolymers
Fluoropolymers are among the most versatile and durable polymers available to manufacturers. But some of the physical properties that make them attractive for very challenging applications, such as their very low Coefficient of Friction (CoF), also cause them to be difficult to print or otherwise mark.
The Q&A below offers insight into some of the points to consider when printing or marking applications manufactured from fluoropolymers.
Q. What are typical fluoropolymer applications that require printing or other forms of marking?
A. Typical applications are ring and band marking of wire and cable, as well as the printing serial numbers or brand names. For medical applications, the markings often are used for branding but also can be indicators to aid in locating a tube in a patient’s body.
Q. Why is printing on fluoropolymers such a complex process?
A. Fluoropolymers typically have non-stick properties that make it difficult for ink to adhere to the substrate. Also, the surface tension of the resin substrate is very low, complicating the wetting of the surface with a wet ink.
Q. Are there limitations on the colors that can be used for printing of fluoropolymers?
A. The limitation for inks used to mark fluoropolymer substrates is that they have to be able to withstand high curing temperatures, as this is the adhesion mechanism. This limits the selection of the colorants to very heat-stable pigments. Collaborate with your supplier to determine which colors are available for your application.
Q. Why are low temperature inks recommended for printing on fluoropolymers ECTFE, ETFE, and PVDF?
A. Although commonly called Low Temperature inks, in fact these still need to be heated during curing - so they are in practice heat curable inks.
But because the melt temperatures of ECTFE, ETFE and PVDF are lower than those of other commonly used fluoropolymers, a lower curing temperature material is needed, hence the Low Temperature designation.
Q. How permanent is the printing on a cable or other part made from fluoropolymers?
A. When the material is cured properly, the print will melt into the top layer of the surface of an application. This provides a very good adhesion to the fluoropolymer, and an extremely long-lasting mark.
The printing and striping inks used with the fluoropolymers PTFE and FEP are formulated from the same resins as the substrate. The use of the same matrix material creates a uniformly melted top layer.
Q. Do I require special equipment for printing on fluoropolymers?
A. No, multiple printing techniques can be used, including bath-and-wheel printing, tampon printing, screen printing and gravure marking. Unfortunately, inkjet printing is not possible.
Q. Are printing/marking solutions available that meet Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) legislative standards?
A. Yes, there are solutions available that will help your company and its applications stay compliant with the REACH legislation.
Q. What is the benefit of water-based formulations for printing inks? Is there any downside to water-based inks?
A. The striping and printing inks for FEP and PTFE are water-based. No solvents will be introduced in the manufacturing site, and they are environmental friendly. The Low Temp inks recommended for printing on fluoropolymers ECTFE, ETFE, and PVDF also are water based, but do contain solvent.
Q. What is a typical application for the Low Noise Dispersion (LND) coatings?
A. There are different types of LND dispersions in use. One of the most common is selected mainly to serve as a coating on low-noise coaxial cables with a dielectric core of PTFE. The PTFE LND-based coating functions as a shield that reduces the influence of outside radiation.
The PTFE LND will reduce RF noise in coaxial cables when they are in motion (e.g. EKG sensor cables). Low-noise coaxial cables (e.g. RG-404/U) are defined in U.S. military specification MIL-C-17E.
LND dispersion could also be selected as an antistatic coating on PTFE-impregnated glass cloth, or as a resistance carrier for heating bands.
Q. Are all fluoropolymer printing processes done offline, or can some be done online?
A. Printing can be done inline, after an extruder. Talk with your ink supplier to help realize a swift and efficient installation of your equipment.
Do you have more questions about printing or marking fluoropolymers?
Avient offers a full range of colorant or additive concentrates, and specialty compounds, based on these materials, as well as the necessary printing and marking inks. Put our experience to work for you. Contact us to learn how our fluoropolymer solutions can enhance your products.