Study on the Impact of Dye – Sublimation Printing on the Eff ectiveness of Underwear

This study deals with the eff ect of dye-sublimation printing on the performance of underwear. Two groups of polyester knitted fabrics were analysed. The change of tree selected groups of properties was investigated before and after the application of dye-sublimation printing, namely durability (breaking force and elongation, abrasion resistance and pilling resistance), physiological properties (water vapour permeability, air permeability) and colour-fastness (resistance to rubbing, to domestic and commercial laundering, to perspiration). Further, the structure changes of fabrics (thickness and density) during heat pressing both without application of dyes (without transfer printing on material) and with application of dyes were also studied to analyse the aff ect extent of printing conditions (particularly pressure and temperature) on total wear comfort printed fabrics. The results show that the tested materials meet requirements in terms of colour-fastness to rubbing, to domestic and commercial laundering and to perspiration to a very high standard (grade 5). In terms of abrasion resistance and pilling resistance the material also showed high resistance. The air permeability for both fabrics decreased by about 40% in comparison with the value obtained before printing and the mechanical properties slightly increased (about 8%). This was due to an increase in the stitch density and a decrease in the thickness, therefore reducing the porosity of the material for printing conditions, mainly due to the infl uence of the pressure and temperature within the heat press machine.


Introduction
Heat transfer presses have been used for the dye-sublimation printing of polyester and other fabrics for over 30 years.e process is environmentally clean and the vibrant colours and clear images give the process many advantages [1].Heat Transfer printing is the primary step in apparel manufacturing operations utilizing the increasingly popular agile manufacturing.It is the perfect medium for the demands of today's marketplace -short run and sample production [2].Digital-print textile technology and heat transfer processing have the advantages of facilitating the reproduction of several colours, reducing post processing, and lowering equipment investment and maintenance [3].Because it is simple, cheap, easy to reproduce colour, and does not need post treatment, this process has its advantages when looking for a quick and easy way to print on fabrics [4].In his papers, [5,6], Wu found that heat transfer temperature and dwell time are the two key factors a ecting colour reproduction on polyester fabric.Heat presses can heat a transfer up to 218 degrees C and can press between 40 and 80 psi (0.276 and 0.552 MPa) [7].
is value only represents the amount of air pressure brought to the machine and is displayed on the air gauge.
e actual applied pressure (2 to 6 psi) is calculated from the cylinder size and the plate area [8].A heat press is the machine used to transfer a design from transfer paper to the object.Transfers done with a heat press are permanently adhered to the object [7].
e high pressure and temperature have a considerable e ect on the properties of the printed fabrics.Many scienti c papers have dealt with the topic of heat transfer printing or dye-sublimation printing and have tested the quality of printing and researched the dye used.However, it is also necessary to look at the changes in the properties of the fabric (linked to the structure) which have been dye-sublimation printed.It is assumed that the changes in the fabric due to dyesublimation printing are induced by the following parameters: temperature, dwell time and pressure.ese changes are re ected especially regarding comfort (air permeability, water vapor permeability) and durability (strength, elongation, thickness).
e following studies have investigated print quality and the properties of the applied dye in the process of heat transfer printing or dye-sublimation printing.Abd El-alouth [9] examined the feasibility of transferring colour from a screen-printed polyester fabric to another polyester fabric using the heat transfer printing technique.Guo [10] researched parameters such as printing density, printing colour gamut, the colour e ciency of heat transfer printing papers and fabrics and Hallas [11] examined the heat transferability of dyes on polyester bres.Kiatkamjornwong [12] compares textile print quality between inkjet and screen-printing onto cotton fabrics and, furthermore, examines the properties of the printed fabrics, such as sti ness, air permeability and crock-fastness.Mikuž [13] reviews the current and future trends of textile digital ink-jet printing and compares the production costs of di erent ink-jet and screen printing technologies.Underwear is the rst layer of functional clothing and therefore must be comfortable enough so as not to infringe upon the functionality of the whole clothing system [14,15].For this reason, this paper also deals with the physiological properties of printed fabrics.
2 Methods e aim of this study is to observe the impact of dye-sublimation printing on a selected group of properties of fabrics that are commonly used in corset production.
e investigated knitted fabrics were printed by multipurpose inject and sublimation plotter JV4-130 produced by MINAKI.ere no special pretreatments were applied to tested materials before their printing.e dispersive dye and classical heat transfer paper (weight 100g/m 2 ) were used.Two groups of knitted fabrics (Table 1) were analysed in terms of their physiological properties, colourfastness and durability.Changes in these properties were investigated before and a er dye-sublimation printing.e changes in the structure (thickness and density) were studied and, subsequently, the changes in the physiological properties of the fabrics during heat pressing without application of dyes (without transfer printing on material) were also studied.e same conditions of temperature, pressure, dwell time and type of dye were applied as for the original transfer printing.e printing parameters were also set the same for all tests.is experiment was designed to measure the e ect of the dye on the material properties tested and the e ect of transfer dye conditions during heat pressing.e printed area corresponded to about 85% of the original (unprinted) fabric surface.e materials tested comply with the requirements for dye-sublimation printing.All experiments were carried out in a standard atmosphere for testing in line with Standard ISO 139:2002.
e optimal parameter setting of dye-sublimation printing (dye, pressure, temperature, time) has been examined in several studies [5][6][7][8][9][10].Based on these studies, on our own experiment and on our previous study [16], the optimal printing conditions were set (using discontinuous heat press): heat transfer temperature -180 °C, dwell time -60 s and pressure -12 kPa.A plate heat press machine was used for the dye-sublimation printing.
e changes in the following properties of the knitted fabrics were investigated: e conditions for taking measurements in all the tests comply with the aforementioned standards with the exceptions of the air permeability measurement.In this case, the pressure gradient was set at 10 Pa due to the properties of the tested materials and due to test equipment used (SDL M0215).Average values in the testing of the properties are based on ve independent measurements.e coefcients of variation for all tests do not exceed 5% and are there for not statistically signi cant.

Colour-fastness
e results show that the tested materials meet requirements in terms of colour-fastness to rubbing, to domestic and commercial laundering, and to perspiration to a very high standard (grade 5) (Figure 1).In terms of abrasion resistance and pilling resistance, the material also showed high resistance.Tests were conducted using the Martindale machine.In the abrasion resistance test, no crossing points of the fabric frayed through a er 50.000 rpm: only the colour of the fabric changed from grade 5 to grade 3 (Figure 2).e piling resistance tests were also very good: grade 5.

Physiological properties
Interesting di erences were investigated regarding both the changes in the air permeability of the tested fabrics and their mechanical properties (breaking force and elongation at break) a er printing.e air permeability for both fabrics decreased by about 40% in comparison with the value obtained before printing (Figure 4) and the mechanical properties slightly increased (about 8%). is was due to an increase in the stitch density of about 15% (Figure 8) and a decrease in the thickness of about 18%, therefore reducing 0 Fabric A Fabric B before printing after printing without dye after printing with dye  the porosity of the material (Figure 7) for printing conditions, mainly due to the in uence of the pressure and temperature within the heat press machine.Further water vapour resistance (R et ) was investigated by SGHP 8.2.Water vapour resistance is water vapour pressure di erence between the two sides of specimen divided by the resultant evaporative heat ux per unit area in the direction of the gradient.Values of R et decreased slightly a er printing (Figure 3) for tested materials.is could be due to the change in the thickness of the fabrics a er printing.A study by Havenith [14] supports this theory.However the R et values of the tested material fall inside of the limits of 0-6 R et that means the knitted fabrics have very good water vapour permeability.

Durability properties
Mechanical properties were investigated both in the course and in the wale directions before and a er

Structural properties
e e ect of temperature and pressure during transfer of dye to the fabrics (inside the heat press machine) led to an increased compression of the tested materials (Figure 7) and structure densi cation (Figure 8).e most considerable change of the fabric structure was noticed a er printing without dye.It means that the dye itself contributes to the change of fabric structure (and subsequently to others observed properties) very low degree.Figures 9 and 10 show the changes in the structure of the material (before and a er printing without dye) using an image analysis system called 'NIS Element' .e change of durability, physiological properties, colour-fastness and structure changes of fabrics (thickness and density) was investigated before and a er the application of dye-sublimation printing, according to corresponding technical standard for textile metrology.
e printing conditions (for used discontinuous heat press) were set to following values: heat transfer temperature -180 °C, dwell time -60 s and pressure -12 kPa.
e tested fabrics show both excellent colour-and crock-fastness properties (grade 5) and high durability.Changes mainly occurred in the physiological properties.Particularly the air permeability change was noticed, in the concrete decrease by about 40% in comparison with the value obtained before printing.It was caused by the decrease in porosity; speci cally stitch density increase (of about 15%) and compression thickness of the tested materials (about 18%).ese facts were a ected especially by the dye transfer conditions (pressure, temperature, dwell time) on the knitted fabrics within the heat press machine. is is clear not only from above mentioned fabric structure change but also from image of the material structure (before and a er printing without dye) made by image analysis NIS-Elements.However, the water vapour permeability, one of the most important properties of the undergarment, was not signi cantly a ected.In conclusion, the overall physiological comfort of the tested undergarments showed very similar levels both before and a er dye-sublimation printing, therefore this printing method is suitable for nal application to undergarment production.
breaking force and elongation at break, abrasion resistance and pilling resistance) according to Standard EN ISO 13934 -1:2013 Textiles -Tensile properties of fabrics -Part 1: Determination of maximum force and elongation at maximum force using the strip method, EN ISO 12945-2:2000, Textiles -Determination of fabric propensity to surface fuzzing and to pilling -Part 2: Modi ed Martindale method, EN ISO 12947-2:1998 Textiles -Determination of the abrasion resistance of fabrics by the Martindale method -Part 2: Determination of specimen breakdown; physiological properties • (water vapour permeability, air permeability) according to Standard ISO 11092:1993 Textiles.Determination of physiological properties.Measurement of thermal and water-vapour resistance under steady-state conditions (sweating guarded -hotplate test), EN ISO 9237:1995 Textiles -Determination of the permeability of fabrics to air; colour-fastness • (resistance to domestic and commercial laundering, to perspiration, to rubbing) according to Standard EN ISO 105 -C06:1994 Textiles -Tests for colour-fastness -Part C06: Colour-fastness to domestic and commercial laundering, Part E04:2008 Colour-fastness to perspiration, Part X12:1995 Colour-fastness to rubbing.

Figure 1 :
Figure 1: Evaluation of colour-fastness to rubbing, laundering, perspiration of tested materials

Figure 2 :
Figure 2: Change of colour of knitted fabric B a er test of abrasion resistance

Figure 3 :
Figure 3: Evaluation of water vapour permeability of the tested materials before and a er printing

Figure 4 :
Figure 4: Evaluation of air permeability of the tested materials before and a er printing the course after printing in the course before printinge in the wale after printing in the wale

Figure 5 :
Figure 5: Evaluation of breaking force of the tested materials before and a er printing

Figure 6 :
Figure 6: Evaluation of elongation of the tested material before and a er printing

Figure 7 :
Figure 7: Evaluation of the thickness of the tested materials before and a er printing

Figure 8 :
Figure 8: Evaluation of the stitch density of the tested material before and a er printing

Figure 9
Figure 9: Detail of fabric B before printing by image analysis Nis -elements