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The drop formation dynamics in the drop-on-demand (DOD) inkjet process is studied for model inks including a Newtonian liquid and colloidal dispersions. The ink shear viscosity is a parameter often adjusted in tuning the DOD drop formation process. Apparent shear viscosity measured at low shear rates is currently used to characterize inkjet inks throughout both the inkjet industry and academia. However, during the ejection process in inkjet printing, very high shear rates (above 1 × 10 5 s −1 ) are involved. In this paper, the drop formation characteristics at 10 kHz drop formation rate in a DOD mode of a simple Newtonian liquid are compared with those of a colloidal suspension system which has the same low-shear-rate viscosity as the simple Newtonian liquid, but significantly different high-shear-rate viscosity. Under conditions of good jetting, the drop formation dynamics of the colloidal suspension is similar to that of the simple Newtonian liquid of similar low-shear viscosity, with only slight systematic differences observed. Good jetting is, however, difficult to obtain in the colloidal particle inks, with non-straight trajectories and non-axisymmetric ligaments commonly observed. These observations suggest that evaporation, nonuniform wetting, and particle-related changes in properties play a role when poor jetting behavior is observed for colloidal inks.

Electrospinning at relatively low polymer concentrations produces polymer particles rather than fibers. To study the relationship between solvent characteristics and particle morphologies, PMMA was electrospun from seven different solvents and PSVPh random copolymers were electrospun from solutions in MEK. High-speed photography was used to visualize the particle-formation process. Based on these studies, a qualitative relationship between the solvent properties and the electrospun particle morphologies is discussed. By tailoring the solution properties and electrospinning conditions, particles with different morphologies (porous polygonal particles, solid polygonal particles, hollow spheres, cups etc) can be produced.

A single-end sizing process was developed to eliminate the problems associated with the traditional sizing method. By keeping the yarns separated in slots in the single-end sizing apparatus and drying them individually, less damage to the yarns occurred. In this paper, the process and device developed for single-end sizing are described and the properties of single-end sized yarn are compared with unsized yarn and commercially sized yarn.

Impaction on smooth solid substrates of drops formed by the drop-on-demand (DOD) method was investigated over a wide range of impaction speeds (U0 = 2.21–12.2 m/s), surface contact angles (θ = 6–107°), and drop diameters (D0 = 40.8–50.5 μm). The experimental results were compared with several existing equations for predicting maximum spreading. The dimensionless time to reach maximum spreading ratio, scaled by D0/U0, ranged from 0.6 to 2.99, depending on Weber number and contact angle. Micron and millimeter drop impactions were compared, and the results indicate that scaling based on three dimensionless numbers (We, Re or Oh, and cos θ) is valid, but spreading ratios of millimeter drops are usually slightly larger during the whole process. The difference is ascribed mainly to the effect of gravity. © 2007 American Institute of Chemical Engineers AIChE J, 2007

This paper is concerned with the image quality of lines that were inkjet printed on polyester woven fabric. Lines (ideal width of 0.1 mm) running in the warp and filling directions were inkjet printed on different fabrics, and print quality (line width, edge blurriness and edge raggedness) was assessed. The effects of fabric structural parameters (including fabric, yarn and fiber parameters), finishing (type and pick-up), and ink type on line image quality are discussed. Image quality depended on fabric construction, particularly for unfinished fabrics. The satin fabric had the worst image quality while the image quality on the plain fabric was best. Finishing can improve image quality; however, the type of finish was very important. Acrylic resin finish improved printing quality significantly, but results with polyurethane resin-finished fabric were not much better than for unfinished fabric. A volatile ink reduced wicking and improves line image quality; thus, image quality using the alcohol base ink was better than for the oil or glycol based inks.

This paper presents an experimental study of the effects of particles on spreading and retracting of a single drop impacting on a smooth surface. The results are reported for particle concentrations from 0 to 0.30, different liquids (mixtures of water and glycerin), Reynolds number from 6.1 to 2700 Weber number from 0.0084 to 180, and four different surfaces (thermal oxide coated silicon wafer, silicon wafer, 1,1,1,3,3,3, hexamethyl disilazane (HMDS) coated silicon wafer, and Teflon® film). Drops laden with polystyrene particles coated with calcium phosphate are observed to behave differently from pure liquids, especially on thermal oxide coated silicon wafer, which is the most hydrophilic surface studied. It was found that pure fluid viscosity is more important than apparent viscosity of the particle‐laden fluid in setting the spreading and retraction. At an impact speed of 2 m/sec, the rebound behavior on the Teflon® surface depends on particle volume fraction.

The xerographic process is one of the digital printing technologies with a potential for textile printing. One barrier to the use of xerography for printing textiles is the lack of textile-specific toners that produce the required textile properties. Attempts have been made to produce textile-specific toners through mechanical grinding processes such as jet milling, but mechanical grinding requires that the toner resins be sufficiently brittle. In our previous work, toner compounds containing resins that are sufficiently flexible for the required textile properties could not be ground to the required particle size for xerography. In this paper, thermally induced phase separation (TIPS) is used to overcome this difficulty. Isotactic polypropylene (IPP) and poly(ethylene-co-vinyl acetate) (EVA) are converted into toners by means of TIPS. The EVA polymers meet the flexibility and colorfastness require ments of textile printing.

An experimental and theoretical study is presented on spreading and retracting of a single drop impacting on a smooth surface at room temperature. The experimental study showed the influence of kinetic energy, liquid-solid interaction, and energy dissipation on the impact process. The results are reported for Reynolds number from 180 to 5,513, Weber number from 0.2 to 176, four different liquids (distilled water, n-Octane, n-Tetradecane, and n-Hexadecane), and four different surfaces (slide glass, uncoated silicon wafer, HMDS coated silicon wafer, and Teflon film). A theoretical model based on an energy balance was developed to predict the maximum spreading ratio at low impact velocity. The key novel feature of this model is that the shape of the drop is assumed to be a spherical cap during the spreading process. When compared to models in the literature, the present model not only gives better predictions for low drop impact velocities, but also in most cases gives predictions that are within 10% of the experimental data at high impact velocities.

A new process is being developed to significantly shorten the current process sequence of short-staple yarn manufacturing. Measuring carded web density is critically important in this new process. Typical technologies that might be used to measure card eb density rely on significant density in order to have enough absorption of radiation to work properly. However, the card web has a very low density (about 13 g/m2) that provides very little absorption. In the absence of an inexpensive method for measuring card webs. the research discussed in this paper attempts to determine whether a digital image processing system can be used to measure card web density. The system consists of a camera focused on the web, illuminated by a light source. A good linear correlation is found between the reflected light from a section of card web and the weight of that section.

Air permeability is an important parameter in through-air drying of unbacked tufted carpet. The primary backing of tufted carpet is the dominant parameter determining carpet air permeability. Carpets of identical construction are tufted using woven and nonwoven primary backings, and the effects of primary backing type on air permeability and drying are studied. The carpet tufted with the nonwoven backing has significantly higher air permeability and significantly lower drying time for a constant pressure drop drying process.

A transient two-dimensional mathematical model is developed to simulate the through-air drying process for tufted textile materials. The heat and mass transfer in a cylindrical porous medium and the air flowing around it are analyzed separately. First, thermal and mass circuits are used to analyze the simultaneous heat and mass transfer within the porous medium. Then, the equations of the conservation of mass and energy are written for the drying medium. The resulting system of three non-linear differential equations is numerically solved by an implicit finite difference method. The numerical solutions are compared with experimental drying results obtained using magnetic resonance imaging (MRI) and a laboratory through-air dryer (LTAD).

Magnetic resonance imaging (MRI) and a pilot-scale laboratory through-air dryer are used to study through-air drying of unbacked tufted nylon carpets. MRI is used to study the effect of the vacuum extraction procedure on local moisture distribution within the carpet and to measure local moisture profiles during through-air drying where airflow rate is held constant. The effects of several process and carpet construction parameters on drying are discussed.

The use of laser scanning confocal microscopy (LSCM) to view textile substrates is a relatively new field. It has been used to determine fiber shapes and concentrations of a fluorescent dye in a fiber. However, this technique is limited to very low concentrations of strongly absorbing species. A new technique based on LSCM is developed for obtaining concentration profiles at much higher concentrations where the effects of absorption of the incident light cannot be ignored. Sample preparation is particularly simple. Although this new approach is specific to planar films, it permits the study of dye diffusion in polymers at normal dye concentrations and with dyes that are not traditionally considered fluorescent dyes. The concentration profiles are used to obtain the diffusion coefficient of C.I. Disperse Blue 3 in nylon 6,6 film.

Xerographic printing of textiles was explored. A number of fabrics were printed using commercially available and synthesized polymers as toner vehicles. The polymers were characterized using standard methods (DSC, DMA, tensile tests). The performance of the prints was evaluated using textiles-specific tests (crockfastness, flexural rigidity). It was found that the initial modulus is a reasonable predictor of the performance of the printed fabrics. However, the requirements on toner vehicles for good textile performance (low initial modulus, flexibility) contradict the requirements for production of toner powders by grinding (brittle behavior). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2399–2407, 2001

Through-air dryers are widely used for drying unbacked tufted carpets after dyeing- steaming-washing processes. Since the drying rate depends greatly on air velocity, carpet air permeability is a very important parameter affecting drying time. We study the effects of several carpet construction and process parameters on the air permeability of unbacked cut-pile nylon carpets with woven polypropylene primary backing using a modified Frazier air permeability tester and a laboratory through-air dryer. We then present a model predicting pressure drop over the carpets versus apparent velocity.

Xerographic printing of a number of common fabrics was investigated. The role of the polymeric binder used for the formulation of the commercially available and custom-made toners was investigated. Fabric performance tests (crockfastness), friction tests, and morphological investigations using scanning electron microscopy were performed. The intricate relations of toner and fabric properties with the results of an important overall industrial performance test for fabrics (crockfastness) are discussed. Both cohesive and adhesive toner failure can be important. Improved toner performance was achieved with a thermoset polymer as the toner binder. However, curing times for the thermoset polymer used are not sufficiently short for high-speed industrial printing. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2425–2434, 2000

To develop an easily deinkable toner for office copiers and laser printers, a series of homo- and copolyamide toner resins were synthesized via condensation polymerization of a soy-based dimer acid, 1,4-phenylenediamine, and L-tyrosine (an α-amino acid). The thermal properties of the resins were examined using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). It was found that the glass transition temperature (Tg), melting point (Tm), decomposition temperature (Td), and crystallinity of the copolyamides were remarkably decreased as the content of L-tyrosine was increased. By using both homo- and copolyamides as binders, respectively, two dual-component toners were developed. The triboelectrical charge, particle size, and particle-size distribution of these toners were examined. The printing trials demonstrated that the images of the soy-based toners are similar to those of commercially available toners. However, because of the low crystallinity and high water-uptake ability of the amino acid-containing polyamide, the copolymer is swellable in an alkaline solution. Initial results from flotation deinking suggest that the amino acid-containing toners are more easily deinked, likely due to their high swellability. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1563–1570, 1999

A study of variations in IR absorption characteristics of fabrics with moisture regain and fiber type is discussed. Infrared spectral absorptivities of fabrics are measured over the range of wavelengths from 0.7 to 25 microns. These values are used with the normalized emission characteristics of blackbody emitters to calculate average absorptivities for blackbody emitter temperatures ranging from 500 to 3000 K. Overall radiant efficiencies of the blackbody emitters are calculated by multiplying average absorptivities by the radiant efficiencies of emitters in converting input power to IR radiant output power. The absorption characteristics of several fabrics such as polypropylene and wool are measured so that the behavior of hydrophilic and hydrophobic fibers can be compared. Correlation equations are presented for average absorptivities of several fabrics as a function of moisture regain.

Textile printing systems are needed that will meet the requirements of time-driven, demand activated manufacturing. Xerography has the potential of meeting these requirements, but textile specific xerographic toners must be developed to gain acceptance of this technology by the textile industry. One thermoplastic and three thermoset-based toners were evaluated for xerographic printing on fabrics (cotton, silk, Dacron, nylon). The toners were successfully applied to the fabric using xerography, however, toner transfer efficiencies to fabrics were low. The textile print properties were compared with commercial rotary screen and hand screen printed fabrics. Color fastness to crocking (rubbing) varied with type of toner and fabric characteristics such as fiber type and fabric weight. Crosslinking of thermoset toners resulted in crockfastness that was superior to conventional screen print. Surface morphological studies were used to characterize the failure mechanisms occurring during the crocking tests. Wet and dry friction properties of the printed fabrics were studied in an effort to explain the crocking results. Fabric flexibility, a key component of fabric hand, depended significantly on fabric weight. The toner type significantly affected flexibility for the lighter weight fabric, but had little effect for the heavier weight fabric.

We studied the feasibility of using a radio frequency (RF) oven to dry and cure latex adhesive backing on tufted nylon carpet. The drying and curing step in the backcoating operation often limits production speed. Numerous backcoating machines are running at relatively low speeds (in the neighborhood of 15 mpm), which cannot be increased by adding to the oven length because floor space is limited. Since RF ovens generally require much less floor space than convection ovens, we investigated increasing production speeds of dryer-limited backcoaters by retrofitting with RF ovens. Installing an RF oven along with a conventional convection oven, especially as a preheater, offers significant advantages in this regard.

A capillary viscometer developed to measure the apparent shear viscosity of inkjet inks at high apparent shear rates encountered during inkjet printing is described. By using the Weissenberg-Rabinowitsch equation, true shear viscosity versus true shear rate is obtained. The device is comprised of a constant-flow generator, a static pressure monitoring device, a high precision submillimeter capillary die, and a high stiffness flow path. The system, which is calibrated using standard Newtonian low-viscosity silicone oil, can be easily operated and maintained. Results for measurement of the shear-rate-dependent viscosity of carbon-black pigmented water-based inkjet inks at shear rates up to 2 x 10(5) s(-1) are discussed. The Cross model was found to closely fit the experimental data. Inkjet ink samples with similar low-shear-rate viscosities exhibited significantly different shear viscosities at high shear rates depending on particle loading.

During carpet manufacturing, yarn twist setting, wet processing (dyeing, printing, washing, finishing and drying) and backcoating (drying/curing) utilize predominately thermal energy. These processes for tufted carpet along with energy requirements are discussed in this chapter. Energy management of tufted carpet manufacturing processes and the future in thermal energy conservation are also presented.

Textile printing systems are needed that will meet the requirements of time-driven, demand activated manufacturing. Xerography has the potential of meeting these requirements, but textile-specific xerographic toners must be developed in order to gain acceptance of this technology by the textile industry. One thermoplastic and three thermoset based toners were evaluated for xerographic printing on fabrics. The toners were successfully applied to the fabric using xerography, and the textile print properties were compared with commercial rotary screen and hand screen printed fabrics. Colorfastness to both dry and wet crocking (rubbing) was measured. Wet and dry friction properties of the printed fabrics were studied in an effort explain the crocking results. Modes of failure of the prints, based on surface morphological studies, are proposed. Fabric flexibility, a key component of fabric hand, was measured. Toner type significantly affected flexibility for the lighter weight fabric, but had little effect for the heavier weight fabric.

An improved continuous dyeing process for coloration of heavy-weight (60–70 oz/yd2), residential nylon 6,6 carpet is reported. By inserting a slot steam applicator after the dye pad and before the box steamer to preheat the carpet to around 180°F (greater than the nylon wet glass transition temperature of ~150°F), the required dwell time of the padded carpet in the atmospheric steamer is greatly reduced (0.3–0.5 of normal). The improved continuous coloration process provides a route to beck-quality, level-dyed, heavy-weight nylon 6,6 carpets at production speeds 2–3X those of conventional lines.

The dynamics of drop-on-demand (DOD) drop formation for solutions containing polyethylene oxide (PEO) have been studied experimentally. Using a piezoelectrical actuated inkjet printhead with the nozzle orifice diameter of 53 μm, experiments were conducted for a series of PEO aqueous solutions with molecular weights ranging from 14 to 1000 kg/mol, polydispersity from 1.02 to 2.5, and concentrations from 0.005 to 10 wt. %. The addition of a small amount of PEO can have a significant effect on the DOD drop formation process, increasing breakup time, decreasing primary drop speed, and decreasing the number of satellite drops in some cases. The effects depend on both molecular weight and concentration. At lower molecular weights (14 and 35 kg/mol), the effect of PEO over the dilute solution regime is insignificant even at concentrations large enough that the solution does not fall in the dilute regime. As PEO molecular weight increased, the effects became significant. For monodispersed PEO solutions, breakup time and primary drop speed closely correlated with effective relaxation time but not for polydispersed PEO. Effective relaxation time depended greatly on molecular weight distribution. Viscosity-average molecular weight, used in calculating effective relaxation time for polydispersed PEO solutions, did not adequately account for high molecular fractions in the molecular weight distribution of the polydispersed PEOs. A mixture rule was developed to calculate the effective relaxation times for aqueous solutions containing mixtures of monodispersed PEO, and breakup times and primary drop speeds correlated well with effective relaxation times. For our experiments, DOD drop formation was limited to Deborah number ≲ 23.

An apparatus developed for visualizing drop-on-demand (DOD) drop formation and impaction on substrates is described. Using a pulsed laser, a low-speed charge coupled device camera, and signal generators, an imaging system based on flash photography is shown to be able to obtain sharp images with a temporal resolution of 200ns and a spatial resolution of 0.81μm∕pixel. Several steps are taken to minimize the “first drop problem” so that excellent reproducibility is achieved; drop formation is reproducible with a positional variation of 1μm. The visualization system coupled with a motorized stage allows imaging of the impaction of micron-size drops on surfaces. A wave form generator and an amplifier are used to produce the required wave form for a given printhead and ejected liquid. Demonstration of the system for study of DOD micron-size drop formation and impaction on a substrate is presented. The effects of signal wave form on DOD drop formation are demonstrated using a Trident printhead driven by four di...

The dynamics of drop-on-demand (DOD) drop formation have been studied experimentally using an imaging system with an interframe time of 1μs and a spatial resolution of 0.81μm∕pixel. Using a piezoelectrical actuated inkjet printhead with the nozzle orifice diameter of 53μm, experiments were conducted over a range of viscosities (1.0–5.0cP) and surface tensions (35–73mN∕m). The effects of the driving signal, which controls the piezoelectric transducer that produces the pressure pulse to drive the liquid from the reservoir through the orifice, have been examined along with those of liquid properties. The main stages of DOD drop formation, including ejection and stretching of liquid, pinch-off of liquid thread from the nozzle exit, contraction of liquid thread, breakup of liquid thread into primary drop and satellites, and recombination of primary drop and satellites, are analyzed based on the experimental results. The breakup time of liquid threads was found to be dependent mainly on the capillary time based...

A study in which energy measurements were made on a continuous carpet dyeing range is discussed. One objective of the study was to determine the energy con sumption per mass of carpet dyed on a typical range. To achieve this, the two kinds of energy, thermal and electrical, that are consumed in the continuous process were measured on the range. A second objective of the investigation was to identify the energy conservation potential of each step of the continuous dyeing process. Mea surements were made so that thermal balances on the components of the Kuster Range could be generated.

Techniques for analysis, reconstitution and reuse of spent dyebaths have been extended to production winch dyeing of nylon 6 and nylon 6. 6 carpets. Results of in–plant dyeing show a 35% reduction in energy, a 40% reduction in water and a 56% reduction in auxiliary requirements by dyeing in reconstituted baths. Substantial decrease in discharge of pollutants is also achieved. Results suggest that dyeing in reconstituted baths is attractive economically, with a $28 per cycle reduction in dyeing costs and a 1. 5 year pay–back period on capital investment.

A study has been conducted to determine the frictional characteristics of several fabrics used in apparel. The objective was to generate fabric frictional data to help in developing automated assemblies for fabrics. The results revealed that the coefficients of static and dynamic friction between fabrics decreased as the normal force per unit area increased. Wilson's model relating frictional force to normal force and the apparent area of contact closely correlated the data.