As competition increases in the label and narrow web industry, quality control grows in importance. End users are placing stringent controls on the materials they purchase. New materials — adhesives, coatings, substrates — are being developed after extensive research and development. As marketing manager Susan Kuper of Thwing-Albert observes: "Developing these products becomes a balancing act of how much cost can we take out of a product while maintaining different levels of strength, flexibility. This is where testing becomes vital."
Product testing is critical at every step. Just as a substrate, adhesive or ink supplier tests its products before selling them, so label converters also engage in a variety of procedures to make sure their printed and converted products will hold up to customer expectations. Testing equipment is being used more widely in the label and narrow web industry to ensure product quality and to maintain quality control.
In order to maintain consistency in industry processes, various industry associations established technical committees to develop standards manuals. Although there are some overlaps in the standards, the organizations try to cover testing that is universal and relevant to the industry. Some organizations that have set standards include: TLMI (Tag and Label Manufacturers Institute), ASTM (American Society for Testing Methods), PSTC (Pressure Sensitive Tape Council), and AFERA and FINAT (the European label association), the latter two used to meet European standards.
Although testing standards exist, not everyone abides by them, and some even question their importance. One standard everyone seems to agree on as most important, however, is to meet the customer's standard.
The testing equipment featured below has been sorted into four categories: adhesive, ink, substrate and UV testing, respectively.
None of these products or procedures can imitate exact conditions under which the finished product will be used, but the whole idea is to come as close as possible, in order to eliminate potential problems with the finished product. Regular calibration of all products is strongly recommended by all manufacturers and users.
Each method has a desired result, and until the desired standards are met, the testing usually continues. Most companies run the test before and after the job is done.
Among the most common tests in today's narrow web production plant are those that examine adhesive properties. These include tests for adhesion peel strength and release properties.
Chemsultants International, of Mentor, OH, manufactures the ChemInstruments AR-1500 TLMI Adhesion/ Release Tester, which is designed to be versatile and can run tests following TLMI, ASTM, PSTC, AFERA and FINAT standards. Pull speeds and test angles are adjustable to meet the requirements. According to company president Richard Muny, Chemsultants is the only manufacturer whose products all meet industry standards.
The AR-1500 can be used to run routine in-plant tests or in-depth analysis of adhesive performance data. On screen prompts direct the operator through setup, testing and file directories. The color data display instantly produces a graph and shows the average, high and low values for each test as it comes to an end. A file name is automatically assigned to each test as it is displayed. Tests can be saved to disk or directed to a network computer for archiving of data.
Testing Machines Inc. of Islandia, NY, markets its LabMaster Release and Adhesion tester, which is available as a field retrofit to existing TLMI release and adhesion testers and monitor/peel testers, or as a complete release and adhesion testing system. As technical engineer Anthony Vena explains, the LabMaster system is designed to remove operator variability from the test procedure by controlling the speed and the angle of measurement specified with a PC, prompting the user through the test cycle with graphic images and touch-screen simplicity. It provides simple analysis of raw data collected from the complete pull for immediate feedback of test results. This system also provides accurate, repeatable high-tech data with minimal operator training or effort.
Thwing-Albert's EJA Universal Materials Tensile Tester is capable of testing strength properties of materials as well as peel and adhesive strength. As it is a universal machine it is effective for a number of applications. With fixtures (various add-ons that allow testing of different parameters) this one tester can measure friction, peel (90° or 180°), probe tack, loop tack and others.
Thwing-Albert's Friction/Peel Tester is a horizontal tester that comes with fixtures, such as a sled, that provide information on the static and kinetic coefficient of friction as well as a number of peel tests. Information about friction indicates how well the material will receive the ink or coating. Peel adhesion is the force required to remove a pressure sensitive label from a standard test panel at a specified angle and speed after the label has been applied to the test panel under specified conditions and for a specific time period.
ChemInstruments' LT-105 Loop Tack Tester uses an electronic load cell and digital data acquisition system to measure the tack force of an adhesive coated product. Tack is the property of a pressure sensitive label that causes it to adhere to a surface instantly with a minimum of pressure and contact time. It is the feeling of stickiness obtained when the surface of an adhesive is touched or when a label is applied to a surface and quickly pulled away.
ChemInstruments TT-100 Rolling Ball Tack Tester offers another way to test tack. Simply by allowing a metal ball to roll down a slope, it quantifies the ability of an adhesive to adhere quickly to another surface, while meeting the standards set by PSTC.
Testing Machines has a Lab Master probe tack tester that provides accurate, repeatable measurements. Test types include adhesion, tack, quick stick, cohesion, and other properties. The instrument allows precise control of dwell force, times and speed to obtain reliable, repeatable test results. One feature of the instrument is its ability to accurately control user-specified rate of loading, which means the user can control the amount of contact pressure that's applied to the material, in terms of its weight. The weight is simply entered into the PC which accordingly applies the desired pressure.
Shear testing is another method to test the strength of an adhesive. It is accomplished by exerting enough pressure to separate the adhesive from the bonded material. The force exerted is distributed over the entire bonded area at the same time. Strengths are recorded in pounds per square inch, or in minutes or hours to failure. The longer it takes for an adhesive to separate from its material the better, depending on its intended use.
According to Faye Marshburn, research and development chemist at Sonoco Products research lab in Hartville, SC, where shear tests are performed regularly, any shear test that falls below the 10-hour mark is considered bad. Sonoco uses mostly ChemInstruments testing equipment.
Dow Industries, a prime label converter in Wilmington, MA, has a fully-equipped testing laboratory in which label products are put through numerous tests. Scott Boucher, the company's quality manager, says there is always a chance that they will not be able to create the exact conditions in which the finished product will be used, but they try to get as close as possible. Dow does its testing before and after the job is completed. At the end of the production run, labels go through what is called a "final sign off station," where they are tested again to make sure that they meet all of the company's standards as well as the client's requirements.
Dow Industries uses a Tenney Environmental Chamber to simulate various temperature and humidity conditions. In this machine, labels are subject to extreme physical environments to test if they can withstand the kinds of conditions they might be exposed to. This device, says Boucher, is used to test substrates and adhesives. The Tenney Environmental Chamber is available through a division of Lunaire Limited, Williamsport, PA.
There is a variety of equipment to test ink adhesion and density. Boucher highlighted some of the more common devices used to test inks at Dow Industries.
A densitometer measures reflected or transmitted light. A reflection densitometer is used as a control instrument to check the uniformity and consistency of print color. It also measures the density of color, ink thickness, fountain solution and dot percentage.
The Sutherland rub test is performed to determine the durability and abrasion resistance of the printed surface of a label. A label is attached to the device and a similar sample label is attached to a weight. The two samples rub against one another at at controlled speed and for controlled cycles, usually about 400 strokes. Once the rubbing stops the samples are examined to see if the ink has worn off or if it's durable enough to withstand handling and transportation.
A GA-Cat, like the Sutherland rub tester, tests the label's and the ink's ability to withstand abrasion, but instead of testing the labels in a horizontal motion, the GA- Cat tests them in a vertical motion. Both testers, the Sutherland and the GA-Cat, can test label-to-label abrasion but the GA-Cat has abrasion receptors that allows much more in-depth abrasion testing.
Whereas the Sutherland rub uses standard weights (2psi, 4psi, etc.) to create the abrasion force between labels, the GA-Cat allows the user to dial in the exact amount of pressure in pounds, and offers other variables as well.
GA Cat is available from Gavarti Associates Ltd., Milwaukee. The Sutherland rub tester is available through Danilee Co., San Antonio, TX.
The fadeometer tests whether the inks used will withstand the strong rays of the sun. A pressure sensitive label is placed in a box containing lamps that simulate sunlight, and are left exposed for a standard duration to test the effects of the sun on the ink.
The drawdown test is a fundamental laboratory technique which is used to evaluate interactions between flat surfaces, such as film, foil, and paper and a myriad of inks, coatings, paints, suspensions, adhesives, colloids, powders. It is a method of roughly determining color shade by drawing down a small amount of ink using a Meyer rod.
Metering or Meyer rods are a proven way to apply uniform coatings to paper, film, sheet, foil, and non-wovens. Opacity, color match, gloss, tack strength, drying rate, coating weight per unit area, dye uniformity, and other attributes can be easily evaluated.
A tape test is performed to test the durability of the ink or simply to see if the ink cracks. There are two ways to perform the tape test. One way is the cross hatch test: A checkerboard pattern is scratched with a razor blade onto the inked surface, and then a piece of tape is placed on it; without any dwell time the tape is pulled off to see how much of the ink comes up with it.
A second form of tape test is called the straight-up tape test. Once again the tape is placed on the label, but this time it is peeled off after a 30-second delay. Again, this test is to see if the ink cracks.
Beyond testing for strength and density of inks, converters can also determine if colors are correct by utilizing color proofers." Beta Industries of Carlstadt, NJ, saw this need and manufactured color proofing viewers which are hand-held and measure at various magnification levels. They are used to isolate problems, by bringing up contrast of colors, showing specific characteristics to pin point where the color matching goes wrong. Once the problem is located than proper course can be taken to fix the color.
Stuart Serchuk, director of sales and marketing at Beta Industries, points out Beta's Perfection Series — Gray Custom Color Bars. Beta Custom Gray Balance Color Bars feature yellow, magenta, cyan, black and gray balance targets in every ink key zone, in addition to 25 percent, 50 percent and 75 percent dot gain targets, resolution targets and trap colors.
"With a glance, the press operator can detect the slightest changes in gray balance and color density," Serchuk says. Then using a densitometer, the press operator can quickly determine which ink key needs to be adjusted to maintain perfect gray balance.
Thwing-Albert's ProGage Thickness Tester is a quality control instrument used to measure substrate thickness. Uniformity is vital for many reasons, but primarily to keep the production line running smoothly. In addition to making sure the production line is working correctly, thickness uniformity is important for end-product performance. If the material is going to be used for a wrapper or bag, it is important that the thickness is uniform and meets the spec so that tears or ruptures don't occur in thinner areas. It is also important when converting a substrate. The thickness must be uniform because you provide the machines that convert material with the gauge or thickness and if there is variation you may experience runnability issues.
Thwing-Albert's Bending Stiffness Tester measures the bending stiffness and bending strength of paper and board as well as polymers, foils and synthetic papers used in the label industry. The Dynamic Contact Angle Tester measures the contact angle of a substrate, which shows how well and how quickly the material will absorb an ink or coating.
A dyne test is performed to examine surface energy. Louise Calliouet, marketing manager at UV Process Supply of Chicago, IL, explains: "If an ink is to be compatible with a substrate, the surface tension of the ink must approximate that of the substrate." Surface tension is measured in dynes/cm. The surface tension of a substrate must be higher than that of the ink it receives so that the ink will "wet out" and adhere properly. Adjustment of dyne level is achieved through corona treatment.
The level of treatment can be determined through the use of dyne pens, such as the Con-Trol-Cure model marketed by UV Process Supply. These chisel-tip marking pens provide a quick, clean and easy method of testing treatment levels on plastic films. Converters who have corona treaters on their presses can adjust the surface tension by the proper corona discharge, and thereby ensure good ink adherence.
According to Russ Smith, president of Diversified Enterprises of Claremont, NH, several types of dyne pens are available. Most rudimentary is a nominal go/no-go tester: Above a certain treatment this pen marks the surface; below the level, the ink disappears. The pens identify and permanently mark the treated side of polyethylene and polypropylene. Smith says, however, that the pens' initial accuracy is undocumentable and their design is subject to contamination. A second style of dyne pens is formulated at several dyne levels, enabling the user to test over a range of treatments. Generally, these markers are interpreted based on which dyne level takes closest to two seconds to form ink beads. These test markers are easy to use and, when first used, often quite accurate. Unfortunately, Smith continues, their "magic marker" style nibs serve as conduits for contamination of any kind, including machine oils, airborne lubricants and plasticizers.
Thus, Diversified Enterprises markets its own dyne test marker, the Accu Dyne Test Marker Pen, which is based on a valve tip applicator. In this model, where the resting part of the pen is kept away from the fluid storage part of the pen, there is no wicking from the substrate. By pressing the tip firmly down, the valve is opened and fresh fluid floods the tip; this flushes it clean, and allows the tester to lightly pass over the sample to accurately determine dyne level. Results are based on how long the test solution takes to form beads on the sample surface.
UV Process Supply's Con-Trol-Cure Compact Radiometer is used for measuring UV radiation levels in high intensity, high energy curing environments. The radiometer is a self-contained UV dose measuring instrument small enough (4" x 6" x 1¼2") for use in most UV curing ovens. One side is exposed to the radiation and the other side contains a digital LCD which displays direct energy readings in Joules/cm2. The aluminum housing can withstand exposure to oven temperature up to 1,000° F (538° C) as well as intense vibration and shock.
Designed for web offset, flexo, 3D screen and other systems incorporating inaccessible UV and high energy EB curing systems, the Rad Check test strip is a UV dosage measurement device which can be wrapped completely around a roller or cylindrical object, or measure high EB dosages. Each test strip includes three sections: UV/EB sensitive tab, pressure sensitive adhesive tab, and handling tab.
Another testing procedure used at Dow Industries involves simulation of a product filling line. The AGR line simulator, which the company uses, is designed to provide an accelerated, reproducible and standardized laboratory abuse treatment that simulates the abrasions characteristic of normal filling lines.
The product is available from AGR International, Butler, PA.
The above mentioned products are just a sampling of the many testing devices available today. Not all of these tests are performed by every converter, but every converter most likely performs at least one or two of them.
Some see testing as an investment and a value added tool to improve customer satisfaction by maintaining quality control; others see them as unnecessary. Randy Barlow of Superior Label Systems, Mason, OH, says, "We do only a few basic tests, and they are done to maintain quality control. Our customers don't ask us to run tests."
After all is said and done, "need based" may be the best way to describe the use of testing equipment.