For the Business of Apparel Decorating
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92 || P R I N T W E A R M A Y 2 0 1 6 S creen printing inks have seen a tremendous transformation from their original formulations. Ink manufacturers have modified plastisols in hundreds of different formulas in order to meet the demands of the textile screen printing industry. Some polyester fabrics being manufac- tured today are produced with low energy dye stuffs and poor fabric processing pro- cedures, which result in a greater potential for dye-sublimation and migration. Due to this fact, plastisols now come in a variety of formulations offering lower curing tem- peratures. Here, we will review the variables of the process and how to best achieve the desired results, regardless of the substrates' composition. DRIVING FACTORS IN THE MANUFACTURING OF PLASTISOLS The first plastisols that were introduced to textile screen printing had little resemblance to the inks manufactured today. The early plastisols were thick and tacky as the con- cept of product user-friendliness had not yet been considered. The primary purpose of the early plastisols was opacity to prop- erly cover dark athletic fabrics. Thus, the first cries for change from garment decora- tors were for a product that would be easier to use and opaque. From there, plastisol products evolved fol- lowing a laundry list of different demands to the multitude of products we have today to address countless applications. Manu- facturers of textile screen printing plastisol now have to consider product performance parameters which include: • Printability (including flow and thixo- tropic characteristics) • Opacity • Color • Flash-drying performance, including after-flash tack • Matte-down characteristics • Build up • Gloss • Elongation • Durability • Cure temperature, and • Bleed resistance Today, we have plastisols which not only address these issues, but inks that cure at different tempera- tures in order to address varying levels of bleeding potential from the wide variety of fabric composi- tions currently offered on the market today. FABRIC CONSIDERATIONS (A BRIEF HISTORY) In the early days of polyester fabrics, the product was primarily produced domes- tically. This meant a standardized manu- facturing and dyeing process where the polyester dyes were set to withstand 360 degrees F before the threat of dye-subli- mation would occur. This was a rather comfortable situation for screen printers, as the only threat of migration or sublima- tion came from either under-curing the ink film, or over-curing. This made life simple; properly cure the ink film and all was good. Unfortunately, it did not remain that simple. Following the signing of NAFTA (North American Free Trade Agreement), apparel manufacturers began producing apparel in foreign countries where the manufacturing cost was a fraction of that in the U.S. It was at this point that cheaper fabric dyes and dyeing procedures were utilized in or- der to reduce cost. It was also at this point that the dye-sublimation points of many polyester fabrics began to drop, leaving the textile/plastisol screen printer and ink manufacturers scrambling to address dye sublimation temperature threshold points that were nearing the fusion point of stan- dard plastisols. It is not difficult to find synthetic fabrics that will sublimate at or below 320 degrees F. Although the original plastisols were manufactured for athletic applications, the actual variation on fabrics were minimal compared to today. Now we are faced with fabrics such as polyester, cotton, blends, nylon, Lycra, rayon, and more. This list in conjunction with the count- less number of fabric weights, contents, and types can leave many scratching their heads as to which product is best for their given application. Considering the vast number of fabrics offered and temperature sensitivity that many fabrics possess, we now have plastisols which cure at varying temperatures (less than 320 degrees F) to address these issues. LOW TEMPERATURE PLASTISOLS Although faster fusion plastisols have been on the market for decades to address heat sensitive fabrics, the need for low-fusion plastisols is primarily geared towards heat sensitive/synthetic fabrics which pose the greatest degree of bleeding or sublimation. Modern plastisol inks cure anywhere from 300 to as low as 270 degrees F. There are numerous underbase products available which are designed for problem fabrics and cure at lower temperatures. Aside Plastisol Curing Understanding the Variables of Plastisol Cure Temperatures B Y R I C K D A V I S Rick Davis is the southeastern sales manager for the Triangle Ink Com- pany. He is a veteran of the textile screen printing and manufacturing industry. His background includes contractor management, plant man- agement, consulting, apparel manu- facturing, and quality control. Davis is a member of the Acad- emy of Screen and Digital Printing Technology and is a regular contributor to industry publications and speaker at industry trade events. You can contact Davis at rickd5050@yahoo.com.