Volume 4, Issue 3, Spring2005 Behavior of Prepared-For-Print Fabrics in Digital Printing Traci May-Plumlee, Assistant Professor Textile and Apparel, Technology and Management 2401 Research Drive, Box 8301, NCSU Raleigh, NC 27695-8301 [email protected] 919-513-4196 JiHyun Bae Textile and Apparel, Technology and Management 2401 Research Drive, Box 8301, NCSU Raleigh, NC 27695-8301 ABSTRACT Engineered print design for sewn products can reduce material waste and facilitate customized design of textile products. But, digital printing systems must produce output reliably and consistently for integration into a production process. This study examined changes in dimension and grain alignment of digitally printed and post-treated prepared-for-print (PFP) cotton fabric. Following post-treatment, substantial shrinkage and some skewing of the printed design was found. Furthermore, dimensional change results from one fabric were not predictive of results for a second fabric. These performance concerns impact end product quality and adaptability to the production environment. Future work should focus on delineating an optimum set of pretreatment conditions for PFP fabrics that will result in proper grain orientation and minimal, predictable shrinkage. Keywords: Digital textile printing, Print Design, Engineered Print, Ink jet printing, Prepared-for- print Fabric , Printing Quality Introduction supporting improved nesting of patterns for cutting and facilitating development of Digital technology for printing on customized textile design without limitation textiles makes it possible to step forward to in size of repeat or number of colors in the mass customization, consumer designed design. This technology can be applied to products, and innovative aesthetic design other industries as well, including home possibilities. With the expanded capability furnishings [1]. afforded by powerful CAD systems and textile machinery improvement, engineered To reach their potential, digital print design has been studied for mass printing systems must produce output customization and just in time production reliably and consistently for integration into applications in apparel. Such engineered a production process. Digital textile printing design can reduce material waste by technology has been adopted by the textile Article Designation: Refereed 1 JTATM Volume 4, Issue 3,Spring 2005 and apparel industry for sampling and short- piezoelectric material, which causes a run production. Currently, printing speed, contraction and expansion. When the inks compatible with the full range of fibers deformation occurs, a drop of ink is ejected. and fabrics, enhanced color yield and color CIJ systems generate a continuous stream of matching are being investigated and are ink drops, and some of those drops are improving. One major component of deflected while others are allowed to contact reliability is consistent and predictable the substrate. CIJ systems can be classified performance of prepared-for-print (PFP) as binary or multiple deflection systems fabrics during printing and post-treating. based on the drop deflection method. In a This paper examines the behavior of binary system, drops are either charged or purchased prepared-for-print fabric in uncharged between the jet orifice and a response to the digital printing process. By charging plate. In a multiple deflection clarifying the behavior of typical PFP system, drops are charged varying amounts fabric s, the challenges of developing an and deflected to the substrate at different integrated digital textile printing system can levels (up to 30). Tincher [2] noted that both be better understood. DOD and CIJ printing systems have advantages and disadvantages for digital One component of a digital printing textile printing. system is the printer. Commercial inkjet printers, developed initially for paper and The main ink formulations used for industrial printing, can be divided into two printing on textile substrates, are based on major types based on printing method; drop- dyes or pigments. The colorants have been on-demand (DOD) and continuous inkjet developed for optimum fixation and a wide (CIJ) [2]. With a DOD system, a drop of ink color gamut. The choice of colorant and its is generated only when required for printing. application, along with the substrate, Two major DOD systems, thermal and determines the resulting properties of the ink piezoelectric, are currently in use. Thermal jet printed textile . Figure 1 shows the ink jet, or bubble jet, systems have a resistor classification of colorants used in ink jet that can be heated by computer signal. The printing. vapor bubble created on the resistor causes a drop of ink to be ejected from the nozzle. In a piezoelectric printhead, the computer imposes an electrical current across a Colorant Pigment Dyes Water-insoluble Water-soluble Acid Reactive Direct Disperse Figure 1. Typical colorants used in ink jet printing [3] Article Designation: Refereed 2 JTATM Volume 4, Issue 3,Spring 2005 Colorant Acid dye Reactive dye Direct dye Disperse dye Pigment Silk, Wool, Cotton, Silk, Cellulose All type of Substrates Polyamide Linen, wool (not used for ink- Polyester fabric jet textile printer) Table 1. Colorant selection for textile substrates [3] Different dyes are used for coloration of be distorted off perpendicular but straight different fibers based on the properties of (skewed), or in a curved line (bowed), or each dye (see Table 1). The color durability, both. Designs printed on off-grain fabric such as wetfastness, and lightfastness, will not be straight if the fabric recovers to a differs for each combination. proper yarn orientation. Also, being off- grain reduces the fabric quality and prevents Unlike printing on paper, in digital the fabric from draping properly or hanging textile printing, pretreatment and post- evenly in the final product. treatment are required to fix the colorants onto the fabrics and yield improved color Consistent color yield is a crucial appearance and durability. Pretreatment factor for printed textile quality. The pre- chemicals cannot be included in the ink treatment and post-treatment of digitally formulations because they affect the printed fabrics affect the consistency of physical properties (such as viscosity) of the color yield. Yang and Naarani studied the ink making it unsuitable for jetting from the effect of steaming conditions on color print head [3]. The post-treatment processes consistency of ink-jet printed cotton [6]. affect dynamically color appearance and Their paper demonstrated the influence of change the fabric properties. Because results steaming time, temperature, presence of of the digital textile printing process vary wrapping paper, and the position of the according to the treatment conditions, it is fabric in the steamer on color consistency, necessary to understand how the printing and also recommended steaming conditions. process and post-treatment impact quality of output in order to predict how fabrics will This study examined changes in respond to the process. dimension and grain alignment of digitally printed and post-treated prepared-for-print Textiles are impacted by (PFP) textiles. Product design based on an pretreatment and post-treatment processes engineered print requires consistent particularly in terms of dimensional stability shrinkage for successful product assembly and yarn orientation in a woven fabric. Lack and minimal grain distortion in order to of dimensional stability often leads to align the printed design accurately in the shrinkage in a textile. Shrinkage can occur finished product. Off-grain fabric can distort when tensions applied during the the final product to an extent that the pretreatment process are released by laundry product is unacceptable. or steam pressing. The resulting dimensional change affects the final product quality and, Methods in the case of a garment, fit. Yarn orientation is commonly referred to as grain in the sewn Two rolls of pretreated 100% cotton products industry. Grain indicates the warp fabric (cotton duck) were obtained from an and weft directions in a woven fabric [4, 5]. industry vendor specializing in pretreated, As a result of the stresses and strains prepared-for-print fabrics. A Mimaki Textile imposed during pre-treatment, warp and Jet TX-1600S, a piezoelectric drop-on weft yarns may not have the proper demand inkjet printer, was used to print the orientation, that is may not lie at right angles samples for this investigation. The first roll to each other, resulting in fabric that is said of fabric was divided into two individual to be off-grain. Usually, weft yarns are sub-rolls and samples were selected from responsible for the distortion, and they may each sub-roll in order to examine the impact Article Designation: Refereed 3 JTATM Volume 4, Issue 3,Spring 2005 of positio n in the roll on fabric behavior. impact of the yarn interlacing pattern in a The test results obtained by testing the two woven fabric (weave structure) was sub-rolls were compared to the results from examined by analyzing the dimensional the second roll in order examine consistency change in a different type of 100% cotton in dimensional change and change in grain fabric (cotton canvas). alignment between two separate rolls. The Sample#1 Sample#2 Samp le#3 Printing direction 300 DPI 72 DPI Plain sample Sample#4 Sample#5 Sample#6 Plain 300 DPI 72 DPI sample 10x10 Warp direction: blue lines Sample#7 Sample#8 Sample#9 Weft direction: red lines 72 DPI Plain 300 DPI sample Figure 2. Diagram of sample arrangement on fabric 7 4 1 · Samples 2_1 3 6 9 through 4_6 follow 8 5 2 the roll #1 54 arrangement. 2 5 8 · Sample 4_7 9 6 3 through 6_7 follow 1 4 7 the order of the Roll #1 Roll # 2 Feeding line of printing 2 3 2 3 1 1 4 5 6 4 5 6 7 8 9 7 8 9 Figure 3. Sample specification Article Designation: Refereed 4 JTATM Volume 4, Issue 3,Spring 2005 Test specimen preparation were drawn on each sample in warp and weft directions for measurement of Samples to be printed were laid out dimensional change.