Study on ink flow of silicone rubber for direct ink writing

Direct ink writing of soft materials is a very promising technology in 3D printing, and the rheological properties of inks are crucial for successful printing. In this paper, the effect of the rheological properties on the printing process of silicone rubber inks is studied to lay a foundation for the configurations of 3D printing process parameters. Also, the shape retention of the printing filaments is studied to provide a basis for the viscosity deployment of the inks. In addition, by studying the die swell ratio of nano-silica-reinforced silicone rubber inks at normal printing speed, it is found that the die-swell ratio is proportional to the ink's relaxation time. Finally, the influence of the configuration of the short-nozzle on the die swell is investigated, and the concave nozzle has a smaller extrusion swelling effect than the convex nozzle and the conical nozzle, providing new ideas for the adjustment of the filament diameter.     

Evaluation of plant-based oils for production of offset printing ink

The oils and solvents are the main components of the printing ink, and the chemical composition of the ink could be harmful or toxic to human health and the environment. Therefore, there is an increasing demand to develop inks containing green, biobased, sustainable, and renewable raw materials instead of petrochemical substances. In this study, flaxseed oil (FO), pomegranate seed oil, plum kernel oil (PKO), and grape seed oil (GSO) were selected to produce offset printing inks. Pinus pinaster (P. pinaster) resin was also used in the formulation of inks to examine the effects of natural resin on ink together with vegetable oils. The phenolic content was analyzed for the resin and oils to figure out their potential antioxidant and bioactive characteristics. Optical and rheological tests were applied to evaluate the printability of the inks. L*a*b*, ΔE, density, and gloss tests were performed for optical evaluation. The viscosity, tack, and rub resistance tests were applied to perform rheological analysis. The biobased, environmental friendly, and self-drying (cold set) offset printing inks were obtained using natural pine resin and three different plant-based oils FO, PKO, and GSO. The printability analysis of the inks figured out the potential usage of plant-based oils in the offset printing ink formulation.     

The use of natural (Pinus pinaster) resin in the production of printing ink and the printability effect

Alkyd resins are generally used in the production of printing inks. All industries look for alternative raw materials in the production of ink with the growing inclination toward using natural products. Resins forming the vehicle of the ink to be obtained from natural resources will provide benefits for the environment, nature, and living creatures. The aim of the study was to promote the use of natural resin in the ink system. Natural Pinus pinaster resin was added into vegetable and mineral oil-based solvents in pure form with alkyd resin in different amounts and ink varnishes of different combinations were prepared. Then, printing inks were produced from these varnishes in pure and hybrid form. Following the assessment of the rheological properties of the inks prepared, printing tests were conducted to assess the printing quality parameters. Ideal mixing ratios of the natural resins in the ink were determined for printability. The environmental importance and advantages of the use of natural resins were discussed. Recommendations were given in line with the results to encourage widespread use of natural resins in near future.     

Usability of cellulose-based binder in water-based flexographic ink

Packaging must have a good commercial appearance and is generally obtained by ink transferred to its substrate. It is important that the ink used in packaging printing is produced from environmentally friendly and sustainable raw materials as well as being suitable for the printing system. The increasing demand in the field of printed packaging and the scarcity of resources to meet this demand have accelerated the search for new sources for inks. For this purpose, inks produced in the laboratory using a modified cellulose-based binder, a commercial acrylic resin and a commercial soybean protein were compared with a commercial ink. As a result of the study, it was determined that the printability properties of the ink obtained by using the modified cellulose-based binder were better than the ink obtained with commercial soybean protein. It was determined that it showed printability properties close to the ink produced with commercial acrylic binders. By using modified cellulose-based water-based flexographic ink instead of other commonly used binders, more environmentally friendly sustainable inks can be produced.     

Partial substitution of nitrocellulose by polyurethane resins in flexographic ink concentrates

The properties of flexographic inks obtained by the partial replacement of nitrocellulose (NC) resin with different amounts of polyurethane (PU) resins were evaluated for the statistical planning of mixtures to develop an optimum ink formulation. The formulations were developed using a statistical tool and they were found to present properties predicted by the tool. The results indicate that the substitution of the NC resin with PU resins leads to increased resistance of the ink film to delamination. The system obtained with the partial substitution of NC with PU has higher lamination bond strength than the pure NC-based system. The ink films of the formulations NC-based and NC/PU-based were evaluated by spectroscopy UV–vis, both inks have similar transparency of greater than 95% above 575 nm. When exposed to water, milk, and UV light, ink surfaces showed similar behavior in the atomic force microscope, Fourier-transform infrared spectroscopy, and UV–vis analysis. However, ink formulations with higher PU contents underwent higher photodegradation. Other properties such as the viscosity ink, gloss, coating strength, color, adhesion, and blocking of the NC/PU-based ink film did not vary significantly when compared to those of the standard ink produced exclusively with NC resin.     

Direct ink writing of ceramic matrix composite structures

We present the development of an ink containing chopped fibers that is suitable for direct ink writing (DIW), enabling to obtain ceramic matrix composite (CMC) structures with complex shape. We take advantage of the unique formability opportunities provided by the use of a preceramic polymer as both polymeric binder and ceramic source. Inks suitable for the extrusion of fine filaments (<1 mm diameter) and containing a relatively high amount of fibers (>30 vol% for a nozzle diameter of 840 μm) were formulated. Despite some optimization of ink rheology still being needed, complex CMC structures with porosity of ~75% and compressive strength of ~4 MPa were successfully printed. The process is of particular interest for its ability to orient the fibers in the extrusion direction due to the shear stresses generated at the nozzle tip. This phenomenon was observed in the production of polymer matrix composites, but it is here employed for the first time for the production of ceramic matrix ones. The possibility to align high aspect ratio fillers using DIW opens the path to layer‐by‐layer design for optimizing the mechanical and microstructural properties within a printed object, and could potentially be extended to other types of fillers.     

塑料水性凹印油墨附着性能的研究

采用合适的颜基比和分散剂制备了塑料水性凹印油墨基墨,用与基墨具有良好相容性的树脂溶液调稀基墨,添加各种助剂以改善油墨样品的印刷适性,探讨了颜基比、树脂溶液、助剂对油墨附着力的影响。结果表明:基墨中颜基比为3:1、分散剂为1.5%时油墨在PET和BOPP塑料表面均有较好的附着力,制备油墨时,使用50%的AZ-3808树脂溶液并添加1.5%异丙醇或1.5%润湿剂时,油墨在PET塑料表面具有较好的附着力,使用50%的1424树脂和1437树脂的混合溶液并添加1.5%异丙醇时,油墨在BOPP塑料表面具有较好的附着力。     

数码喷墨用紫外光固化油墨

在数码喷墨领域中，紫外光固化是最近快速发展的一项新技术。本文涉及到数码印刷对所用喷墨的要求，与普通溶剂油墨的区别和油墨配方的选材，最后提及UV固化油墨的发展新趋势。     

An ecological approach to printing industry: Development of ecofriendly offset printing inks using vegetable oils and pine resin as renewable raw materials and evaluation of printability

Petroleum-based solvents and synthetic resins are used as raw materials for the production of varnish, which is one of the main components of offset printing inks. These petrochemical compounds that are released to the surrounding in printing process demonstrates harmful effects on environment and human health. In the light of these facts, this study was carried out to investigate the use of renewable natural resources for offset printing inks production to lower environmental impacts and protect human health. In this study, different vegetable-based offset printing inks were developed with safflower oil (SO); grape seed oil (GSO) and Pinus pinaster resin (PPR) and printability analysis were performed. To understand the effect of pine resin in the ink formulation an ink sample with mineral oil (MO) was also produced. Printing tests were carried out with coated papers and the IGT C1 offset printability tester. Color, gloss, rub resistance, viscosity and tack values were measured on the test prints. Comparison of results with standard values figured out the suitability of using the newly developed offset printing inks for printing industry. The color difference values of color differences were in range of tolerance value. The density value of SO-PPR ink was found as same with standard values while the density value GSO-PPR and MO-PPR inks were measured close to standards as 1.45, 1.42, and 1.46, respectively. The results of printability analysis demonstrated appropriate utilization of the renewable sources for ecological development of offset printing inks.     

Direct ink writing of hierarchical porous alumina-stabilized emulsions: Rheology and printability

Bio-inspired multi-scaled (hierarchical) porous structures have remarkable strength and stiffness-to-density properties. Direct ink writing (DIW) or robocasting, an additive manufacturing (or also commonly known as 3D printing) material extrusion technique is able to create near-net-shaped complex geometries. A new approach of combining DIW, colloidal particle-stabilized emulsion paste inks and partial densification to create tailored architectures of hierarchical porosity on three scales has been demonstrated. The printed and sintered ceramic lattice structures possess relatively high overall porosity of 78.7% (on average), comprising mainly (64.7%) open porosity. The effects of formulation (surfactant and oil concentrations, solids particle size, and mixing speed) on rheology and pore size and morphology have been investigated. The rheological properties (storage modulus, yield stress, and recovery of storage modulus) of the emulsions have been found to delineate the samples with good shape retention from those that slump. Additionally, the internal features of the sintered structures have been analyzed via X-ray tomography and scanning electron microscope. The role of emulsion stability on printability and the internal structure of the prints has been investigated.     

丙烯酸酯单体结构对UV油墨的流变性和分散性的影响

油墨的印刷适性与其流变学性能和分散性密切相关,UV单体是影响油墨的流变学性能和分散性的主要因素。本论文使用不同UV单体研制了UV丝印油墨,重点探讨了TMPTA、EO3-TMPTA、PO3-TMPTA三种单体的结构对研制的UV丝印油墨的粘度、触变性、动态粘弹性和油墨细度的影响。     

Development of novel fluorescent offset ink based on coumarin dyes: Synthesis and properties

Novel fluorescent inks based on coumarin dyes used in offset printing techniques were developed, and their considered chemical and physical properties were investigated. First, the influences of very long alkyd resin, maleic varnish, and phenolic varnish substrates and dye concentrations on the fluorescence properties of these dyes, and secondly, the effects of the presence of fluorescent dyes on the physical properties of inks were examined. Accordingly, two offset inks were prepared: one with an obtained optimum formulation possessing the strongest fluorescence emission in alkyd resin and maleic varnish with a weight ratio of 60:40, and one without fluorescent dyes. Their physical properties, such as rheological behavior, tack, and ink-in-water emulsification, were studied. Both inks showed Newtonian behavior, and the dye induced small increases in the viscosity, thixotropy, and tack values of the fluorescent ink.     

Synthesis of waterborne acrylic copolymer resin as a binding agent for the development of water-based inks in the printing application

In this study, a new waterborne acrylic copolymer resin (acrylic-co-resin) was synthesized to develop water-based printing inks on polyester (PET) film. The synthesized acrylic resin showed good water solubility, high acid value (120 mg KOH/g), about 57% solid content. The developed water-based inks (cyan, magenta, and yellow) exhibited small particle size (<1 μm) and optimum surface energy within required values (31.5, 32, and 30 mN/m) for good adhesion of ink upon PET films. The developed inks also showed good storage stability for 30 days. Further, to evaluate the application performance, the inks were printed on corona-treated PET films at room temperature, and the ink drying time was measured. Further, the inks were printed on the corona-treated PET film to evaluate the application performance. The developed inks showed a short drying time (7–9 s), which indicates their fast drying nature. Moreover, the developed inks showed good printability, color strength, high adhesion, and excellent rub-resistant properties. Thus, the overall results demonstrated the potential of water-based inks in printing applications.     

Recycling of steelmaking electric arc furnace dust into aqueous cyan ceramic ink for inkjet printing process and its printability

Recycling of electric arc furnace dust (EAFD) has great potential for industrial applications, due to its useful metal contents, including zinc. In this study, aqueous cyan ceramic ink for ink-jet printing applications was synthesized using EAFD. More specifically, cyan ceramic pigments were synthesized using an empirical composition of Zn(EAFD)_XCo_1-XAl₂O₄, in which expensive cobalt oxide is replaced by Zn-enriched EAFD. Zn(EAFD)_0.25Co_0.75Al₂O₄, which has a vivid cyan color, was selected as the optimum composition of cyan ceramic pigments for synthesizing aqueous cyan ceramic ink for ink-jet printing applications. To prevent nozzle clogging during ink-jet printing, the cyan ceramic pigments were micronized. The micronized pigments were mixed with distilled water and dispersant to fabricate aqueous cyan ceramic ink. To determine the optimized jettability and printability of this ink, its rheological properties, including viscosity and surface tension, were adjusted and analyzed. It was concluded that the jettability and printability of aqueous cyan ceramic ink produced via ink-jet printing could be enhanced by appropriately adjusting its viscosity.     

Effects on print quality of varying acrylic binder types in water-based flexographic ink formulations

The ink industry is one of the world's largest markets due to the increasing demand for printing inks for the packaging industry. Flexography printing is a well-known promising technology for large-area printing due to its high printing speed and roll-to-roll capability to print economically on a variety of surfaces and is used in nearly in all areas of packaging printing. Water-based inks are considered non-toxic, odourless, and more environmentally friendly options compared to solvent-based inks. Therefore, in this article, the goal was to develop new water-based ink formulation with different acrylic binders for flexographic printing on commercial solid bleached sulphate (SBS) board. Five inks were formulated with four different acrylic binders and compared to a commercially available ink to study their performance. The developed inks were investigated with regard to their print qualities and print characteristics. It was found that the binder type influenced some print quality while the effect was not significant for others. Using flexography printed cyan inks, the ink formulated with the highest molecular weight had the lowest print density and the largest tonal value increase (TVI) observed between 40 and 60 tone values. The same ink had the largest mottle values and variation in topography. For values of print contrast and delta gloss at 75°, although differences were observed between average values, data had inconclusive variation and spread around averages, where no conclusive trends or effects of acrylic binder type on these response factors were observed. Print chroma and dot roundness results were equally close for all printed samples.     

Curing behavior of a UV-curable inkjet ink: Distinction between surface-cure and deep-cure performance

Safety requirements and the need of low-migration UV inks have received increasing attention in the packaging industry. Crucial for the development and design of low-migration UV inkjet inks for migration-sensitive applications is the polymerization degree. In this study, curing-behavior of a black, high purity packaging ink (HPP-ink) was monitored using ATR-FTIR spectroscopy. UV irradiation of HPP-ink led to changes in specific absorption bands of the FTIR spectra due to crosslinking reaction of double bonds. Changes in absorptions bands at 1,408 and 1,321 cm⁻¹ permitted the determination of CC conversion of acrylic and vinyl double bond, independently of one another. In addition, a method was developed which allows the investigation of surface-cure and deep-cure behavior, separately.     

UV-assisted direct ink writing of Si3N4/SiC preceramic polymer suspensions

Direct ink writing (DIW) offers a flexible and readily available processing route for achieving ceramic components with complex shapes and geometries. The successful printing of ceramic green bodies using DIW typically requires the formulation of particle-loaded inks having a narrow window of rheological properties that enable both flow through the nozzle and support the weight of additional layers. Herein, we present a method for DIW that employs UV-curing to enable printing of otherwise unprintable inks. The inks used in this study are suspensions consisting of a commercially available polycarbosilane precursor and silicon nitride, Si₃N₄, powders. A diacrylate cross-linker and photointiator were employed to enable UV-curing. The effect of cross-linker content on UV-rheology and cure depth as they pertain to printing, and slump in self-supported lattice structures, are discussed. UV-assisted DIW produced components of a high degree of complexity, capable of supporting over-hanging structures, low shrinkage, and relatively high degree of ceramic conversion     

Formulation and characterization of black ceramic ink for a digital ink-jet printing

Formulation of black ceramic ink and its ink-jet printability on a glass substrate were investigated. The thermal and chemical stabilities of CoFe_2-xCr_xO₄ and Ni_0.925Mn_0.075Fe_1.875-xCr_xMn_0.125O₄ black inorganic pigments were analyzed with various amounts of Cr substitutions. The ceramic ink was prepared using the pigment composition that demonstrated color stability during the high temperature glazing process with a minimal Cr substitutional amount. After the dispersion stability and rheological property were optimized, the ceramic ink was suitably jetted from a print head as a single sphere-shaped droplet without satellite droplets. To improve the printability of the ceramic ink, the glass substrate was treated with a perfluorooctyl trichlorosilane (PFTS) solution. As a result, the PFTS surface treatment increased the contact angle of the ceramic ink droplets on the glass substrate and effectively minimized the ink spreading phenomena.     

Rheological behavior of multi-sized SiC inks containing polyelectrolyte complexes specifically for direct ink writing

In order to simultaneously improve both the solid loading and rheological behavior of ceramic ink during direct ink writing (DIW) process, the polyelectrolyte complexes have been used as rheological modifiers. Based on the Funk-Dinger function, the maximum solid loading of multi-sized SiC ink reached 63 vol%. The viscoelasticity of SiC inks with different [COOH]:[NH_x] molar ratios was investigated and the mechanism of polyionic chains on rheology was analyzed. When the [COOH]:[NH_x] molar ratio was 1:0.1, the SiC ink exhibited excellent thixotropic behavior and formability. The effect of particle size on rheological behavior of SiC ink was investigated to clarify the correlation between polyelectrolyte complexes and multi-sized SiC.