Think Ahead, Treat it Right
Corona surface treatment allows for effective printing on plastic substrates, as long as converters are ready to prevent snags in the process.
January 2007 by Missy Smith
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“Success depends upon previous preparation, and without such preparation there is sure to be failure.” The profound words of Confucius couldn’t better explain the importance of corona surface treatment prior to printing on plastic materials.
With corona treating, or any surface treatment system, the goal is to increase the material’s surface energy to provide wettability and adhesion. But, treating a substrate can be ineffective when the system is not properly run and maintained. For this reason, converters should be aware of how to effectively process their materials.
Over/Undertreating
When a corona treating system transfers too much or too little energy to a substrate, a host of problems can occur. “Attempting to obtain satisfactory printing results on undertreated materials can result in the use of excessive amounts of ink in an effort to try to make up for the inadequate treatment level, and doing so can have its own set of problems,” says Bruce Stobbe, president of Corotec Corporation. “Overtreatment can result in damage to the material itself, as well as problems with blocking of the material.”
Poor adhesion, low dyne levels, and inadequate wettability can also occur, says Rob Hablewitz, sales manager of Pillar Technologies. He recommends “[establishing] a beginning point for the power level and [working] your way up on power until the anticipated dyne level is achieved; this being done through quality assurance checks of the film. Once the power level is established for the given product at the given speed, note the power level, re-use it next time, and you are assured of desired dyne repeatibility.”
Tom Gilbertson, VP of application engineering for Enercon Industries, agrees that converters can achieve proper treatment levels through trial and error. “Test protocols which include adhesion and bond strength measurements at a variety of power levels should be used to determine the acceptable power level for each substrate employed,” he says. “Material type, material thickness, and even material suppliers are all variables which can impact the appropriate power level. Once determined, the appropriate power setting should become a permanent part of your job specification.”
Jeff Opad, VP of sales for Jemmco, says the best way to ensure accurate treatment is to train operators how to measure watt density. “The formula for calculating watt density is web width (in feet) x line speed (fpm) x number of sides treated (using the same power source) divided into the actual amount of power being used to obtain the desired dyne level,” he says. “Once this concept is understood, then the user can develop a watt density curve using the formula above, for each of the material formulations they run. These watt densities, once identified, will produce the same treat level every time.”
With corona treating, or any surface treatment system, the goal is to increase the material’s surface energy to provide wettability and adhesion. But, treating a substrate can be ineffective when the system is not properly run and maintained. For this reason, converters should be aware of how to effectively process their materials.
Over/Undertreating
When a corona treating system transfers too much or too little energy to a substrate, a host of problems can occur. “Attempting to obtain satisfactory printing results on undertreated materials can result in the use of excessive amounts of ink in an effort to try to make up for the inadequate treatment level, and doing so can have its own set of problems,” says Bruce Stobbe, president of Corotec Corporation. “Overtreatment can result in damage to the material itself, as well as problems with blocking of the material.”
Poor adhesion, low dyne levels, and inadequate wettability can also occur, says Rob Hablewitz, sales manager of Pillar Technologies. He recommends “[establishing] a beginning point for the power level and [working] your way up on power until the anticipated dyne level is achieved; this being done through quality assurance checks of the film. Once the power level is established for the given product at the given speed, note the power level, re-use it next time, and you are assured of desired dyne repeatibility.”
Tom Gilbertson, VP of application engineering for Enercon Industries, agrees that converters can achieve proper treatment levels through trial and error. “Test protocols which include adhesion and bond strength measurements at a variety of power levels should be used to determine the acceptable power level for each substrate employed,” he says. “Material type, material thickness, and even material suppliers are all variables which can impact the appropriate power level. Once determined, the appropriate power setting should become a permanent part of your job specification.”
Jeff Opad, VP of sales for Jemmco, says the best way to ensure accurate treatment is to train operators how to measure watt density. “The formula for calculating watt density is web width (in feet) x line speed (fpm) x number of sides treated (using the same power source) divided into the actual amount of power being used to obtain the desired dyne level,” he says. “Once this concept is understood, then the user can develop a watt density curve using the formula above, for each of the material formulations they run. These watt densities, once identified, will produce the same treat level every time.”
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