Dr. Pekarovicova, professor, joined the Department of Chemical and Paper Engineering in 1997 as a visiting scientist. She teaches courses in the printing and chemical engineering programs.
Particle Size of Pigments for Soywater Based Inks
Prashant Kotkar, Alexandra Pekarovicova, and Paul D. Fleming III, Western Michigan University;
Dipesh Sonar, American Ink and Technology
Most of the commercially available water-based inks are formulated and manufactured using acrylic chemistry-based resins. Excluding from being nonrenewable, they are also non-biodegradable raw materials. Besides being used as resins for water based printing inks, they are used in various different applications, such as in prosthetic dentistry, automotive industry, medical devices, paints, storage tanks, metal buildings, rail car coatings, bridges, pipes, sealant/adhesive, paper and printing industries. Transparent coatings made of acrylics contain of about 20-25 weight% solids and do not meet the requirements of VOC regulations anymore. Therefore, these kinds of materials need to be replaced by some other alternatives that are natural water borne polymer systems,which was the motivation behind the present research. The aim of this work is to develop soy based pigment dispersions for water based inks to replace acrylic one.
Figure 1: Grinding of pigment Hansa Brill Yellow in various devices at different conditions
Soy proteins are obtained through the extraction of soybean oil. Soy protein is mainly used as a food ingredient, and industrially is implemented in adhesives, asphalt additives, resins, cleaning materials, cosmetics, paints, plastics, polyesters and textile fibers (Browner, 1992; Erhan, 1995; Smith, 1996). The basic application of industrial-grade soy protein is as a binder in paper coatings (Ma, 2013). In our previous work, we used soy polymer in the let-down portion of the water based ink (Pingale, 2019; Pekarovicova, 2019). In the current work, soy based resin was used as a replacement for acrylic resin to grind the pigment and also as a let-down vehicle to make fully soy based ink.
Figure 2: Grinding of Hansa Brilliant Yellow with different combination of surfactant and wetting agent (a,b,c blue), and post treatment with ultrasonication (a,b,c orange)
Pigment grinding was done in two different paint shakers, Red Devil Speed Devil and Red Devil Paint Conditioner -both of the mixers have fixed speed, but time cycles are different. Fine grinding was done with an ultrasonic probe. Pigment dispersions were formulated with soy polymer with the aid of several different surfactants and wetting agents. ProSoy 7475, a soy protein was used for grinding the pigments. As controls, acrylic grinding resins were also employed and pigment particle size was compared for both systems using Nicomp 370 laser scattering particle sizing instrument. Organic pigments Permanent Yellow GSO CN 09, Hansa Brill Yellow SGX 03, Ink Jet Yellow 4G, PV, Fast Blue A4R, Hostaperm Green GNX were employed. All of these pigment dispersions were used to formulate fully soy, and soy-acrylic inks. Inks were printed on laboratory flexo proofer.Figure 1 shows particle size of pigment dispersions of different formulations, which were milled with combination of various surfactants and wetting agents with the aim to select the best grinding composition and equipment. It was found that the suitable particle size for ink formulation can be obtained after combination milling in media mill (paint shaker or speed devil) and ultrasonication (Figure 2 ).
Browner S., Soy ink based art media, US Patent US 5167704A, December 1992.
Erhan S., Bagby, M., Vegetable-oil-based printing ink formulation and degradation, Industrial Crops and Products 3, no. 4 , 1995,237-246. 0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510 540 1 Pigment Particle size (nm) Hansa Brill Yellow HBYa -1 Hansa Brill Yellow HBYa-2 (23 min US) HBYb-1 HBYb-2 (15 min US) HBYc-1 HBYc-2 (23 min US)
Ma J., Zhou G., Zhai H., Xiao H., Effect of soy protein polymer on coating coverage and printing performance for coated paperboard, Journal of Science & Technology for Forest Products and Processes: Vol.3, No.1, 2013, 38-43.
Pekarovicova A., Sonar D., Pingale R., Altay B.N., Husovska V., and Fleming P.D., Soy Protein Fluid Inks for Packaging, IARIGAI Conference, Stuttgart, DE, September 16-18, 2019.
PingaleR., HusovskaV., PekarovicovaA., and Fleming P.D., Water based soy inks for packaging, TAGA, March 17-20, 2019, Minneapolis, MN.
Smith, K. Industrial uses of soy protein: New idea, 87thAOCS Annual Meeting & Expo, 7, 11, 1996, 1212-1223.
Screen Printed Moisture Sensor and Its Application On Smart Packaging
Ruoxi Ma, California Polytechnic State University; Alexandra Pekarovicova, Western Michigan University
The hemicellulose–based suspension with nano–fibrillated cellulose (NFC) composite film exhibit outstanding air barrier properties, which supports their applications as bio–based and biodegradable barrier coating on food packaging materials. The hydrophobic property of the hemicellulose–based biopolymer has been greatly improved (MVTR decreased by 49.7%) with crosslinking by using citric acid.
In this work, the crosslinked bio–polymer suspension was applied on solid bleached sulphate (SBS) board with a Meyer rod. Interdigitated electrodes were designed as moisture sensors and then screen printed on the coated SBS board with silver conductive ink. The hemicellulose–based barrier coating layer functioned as a moisture sensing layer. The printed sensor device was calibrated with its absorption and desorption isotherms at 23 °C with the range of relative humidity 20%–80%, followed by characterizations of the sensor’s impedance change with each moisture level ranging from RH 20% to 80%. The breakthrough time was observed for each level of RH by measuring impedance using the LCR meter.
These findings point to the opportunity of coupling the hemicellulose–based barrier coatings with printed moisture sensors in order to boost their capabilities as smart barrier packaging materials.