Graphics Pressrun
For the second pressrun, the same four inks were used with 800 cpi, 2.0 bcm anilox rollers in each station (see Figure 2). Once impression was set and all of the graphics were registered, the press speed was increased to 110 fpm to remain consistent with the first pressrun. A sample was pulled and analyzed for Delta E 2000 and solid ink density on both sides of the press. The CHROMAFINE (PMA) formulation was run on press first and the Delta E 2000 value recorded for the orange ink was too light in color, indicated by a positive delta L* value. Adjustments were made to press speed and impression was increased, but this did not bring the Delta E 2000 value of the orange within tolerance. The anilox roller in the Clemson Orange station was then changed to a 550 cpi, 3.0 bcm to increase ink film thickness and darken the color. The press speed was increased to 115 fpm and the Delta E 2000 of the orange ink fell within the set tolerance for the experiment.
Table 5: The average static and kinetic coefficient of friction (COF) values for each ink type.
The plates, ink chambers, and anilox rollers in the orange and green ink stations were cleaned and replaced with the AquaGreen inks. Due to the Delta E 2000 measurements with the previous orange ink, the 550 cpi, 3.0 bcm anilox roller was used for the eco-friendly ink. Once impression and registration were set, a sample was pulled to measure Delta E 2000 and solid ink density on both sides of the press. The press speed was increased to 115 fpm and the Delta E 2000 value for the orange ink was too light in color for this formulation as well. The impression was increased and further adjustments to press speed were done to achieve the lowest Delta E 2000 value possible with the current press conditions.
A Delta E 2000 value of 3.0 was the lowest measurement attainable at press speed of 100 fpm. Ten samples were taken after running the press at this speed for one minute. Solid ink density and Delta E 2000 measurements were taken from 10 samples of each ink set and the average values for each ink are shown in Table 4.1 and Table 4.3. Again, the target Delta E 2000 values are shown in Table 4.2.
Sutherland Rub Test
Ink drawdowns were completed using a hand proofer with a 500 cpi, 3.0 bcm anilox roller. The five ink samples were used to complete a Sutherland rub test. The Sutherland rub test consisted of 30 passes using a two-pound weight. Differences in the rub resistance of the petrochemical-based inks compared to the eco-friendly inks were observed. Visually, the petrochemical-based inks had better rub resistance properties than the eco-friendly inks. Scuff marks consistently appeared on the eco-friendly ink samples for each iteration of the test. The images in Figure 3 show the visual differences in rub resistance between the CHROMAFINE petrochemical-based inks and the AquaGreen eco-friendly inks.
Coefficient of Friction
The coefficient of friction (COF) test records the amount of force required to move an ink sample and keep it moving for a set period of time. Six drawdowns of each ink color were used to complete this test. Each sample was pulled across the flatbed of a FP-2250 Friction/Peel Tester for a distance of 6-in. The additives within the ink or any coating that is applied on top of the ink can affect how easily the sample moves and the COF value. Generally, waxes and coatings decrease COF values. The average static and kinetic COF values for each ink type are shown in Table 5.
Experiment Findings
The results of the pressrun and the additional ink tests described in this report display the properties of eco-friendly inks (DPA) compared to petrochemical-based inks (PMA). Three of the four inks tested had an average Delta E 2000 measurement of 2.0 or below, compared to the target Clemson brand color. The average Delta E 2000 value for the orange eco-friendly ink was 2.96, which was not within the tolerance of the experiment. Overall, the petrochemical-based inks had a lower average Delta E 2000 measurement than the eco-friendly inks.
Ink drawdowns tested for rub resistance showed that eco-friendly inks did have less rub resistance than the petrochemical-based inks. This may be attributed to the petrochemical-based ink containing a wax or additive to prevent scratching of the ink surface. The PMA ink formulation also recorded a lower average COF measurement than the DPA inks, suggesting the ink may contain wax additives. An important consideration when using eco-friendly inks is that in some instances they may require an additional coating—such as an aqueous coating—to improve rub resistance.
Industry Research
There is an opportunity to expand this research into multiple avenues of the printing industry. This experiment could be augmented by using multiple biorenewable inks on biodegradable substrates and completing tests to determine if these products are compostable. An ink using a high percentage of biorenewable materials, printed on an eco-friendly substrate, could be considered compostable (Sun Chemical, 2018). The use of biodegradable films using eco-friendly inks could transform the flexible film industry, reducing plastic waste. As online shopping increases, it is also necessary to research eco-friendly ink alternatives for corrugated packaging. Research on eco-friendly product alternatives serves as an opportunity to educate consumers on the importance of environmentally friendly packaging.
Conclusions
Eco-friendly ink alternatives are comparable to petrochemical-based inks in regard to color matching using the flexographic printing method. Although the majority of the tested inks were within the Delta E 2000 tolerances, one of the eco-friendly inks was unable to meet the color difference metrics set for the experiment. This could potentially be a drawback for widespread adoption of these products if printers are unable to achieve the same color consistency with eco-friendly inks as with petrochemical-based inks. Further research is needed to discover methods for eliminating these variances in color on press.
The durability of eco-friendly inks is important to consider when deciding if they can be used for a printed piece. However, the addition of an ink coating in order to ensure rub resistance in products where eco-friendly inks are used may not be viable, depending on the added cost to the printer. Additional research in both of these areas would be necessary before more companies begin to use eco-friendly ink alternatives for consumer products.
Limitations
The Delta E 2000 measurements obtained from this study are specific to the use of a PrintKote paperboard substrate, and two water-based flexographic inks—one eco-friendly ink formulation and one petrochemical-based ink formulation. This experiment had a limited sample size. Additional testing would be needed to observe the effects of using other types of eco-friendly ink alternatives or a different paperboard substrate. Between the two pressruns, there were changes in press conditions as classes used the equipment during the academic semester. This could affect the ink buildup on the anilox rollers, ink laydown, print quality and Delta E 2000 measurements achieved for the final run.
Acknowledgments
I would like to thank Mr. and Mrs. Rossini, as well as the FTA Scholarship Committee, for awarding me the opportunity to complete the project. Thank you to my professors at Clemson University, Dr. Ingram, Dr. Woolbright, Dr. Chang, Mrs. Fox, Mr. Cox and Mrs. Edlein, for encouraging me to pursue my research and assisting me with the experiments.
I appreciate Dr. Evan Benbow and the team at Wikoff Color for providing me with more information on eco-friendly inks in the early stages of my research. Thank you to Jim Felsberg and Bruce Marshall along with their team at Sun Chemical for providing the inks for this project. Also, thank you to Wade Harris for providing the substrate and taking the time to discuss the best paperboard options for the experiment. This project would not have been possible without their guidance.
References
Bajpai, P. (2018). Biermann’s Handbook of Pulp and Paper – Raw Material and Pulp Making, Volume 1 and 2 (3rd Edition). (pp. 465-491). Elsevier.
Ginebreda A., Guillén D., Barceló D., Darbra R.M. (2011) Additives in the Paper Industry. In: Bilitewski B., Darbra R., Barceló D. (eds) Global Risk-Based Management of Chemical Additives I. The Handbook of Environmental Chemistry, vol 18. Springer, Berlin, Heidelberg
Sun Chemical. (2018). Going beyond environmental claims: Sun Chemical’s eco-friendly products, combined with responsible manufacturing, can help printers and brand owners achieve sustainability goals [White paper].
About the Author
Anissa Mollett is a May 2020 graduate of Clemson University, earning her M.S. in graphic communications. She earned her B.A. in graphic design in 2017 from Charleston Southern University.
Her passion for art began during her childhood as she transitioned from drawing on her mother’s walls to sketching cartoon characters daily in her notebooks. She decided to turn her passion for design into a career, developing a special interest in packaging and layout design. Anissa’s interest in sustainable packaging stems from her desire to positively impact society through art and design. After graduation, she plans to pursue a career in packaging design as well as opportunities for developing eco-friendly alternatives within the packaging industry.
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