Reactive inkjet printing of polyethylene glycol and isocyanate based inks to create porous polyurethane structures

Reactive inkjet printing offers a direct way to create polymeric structures in situ on a substrate. Therefore, two component polyurethane formulations can be utilized to be used in multicomponent inkjet printing. In this contribution, the use of polyethylene glycol (M = 200 g mol⁻¹), glycerol ethoxylate (M = 1,000 g mol⁻¹), and water (blowing agent) in combination with aliphatic 1,6-hexamethylene diisocyanate or aromatic methylene diphenyl diisocyanate for reactive inkjet printing is evaluated. The inks are jettable on a Dimatix DMP-3000 inkjet printer using a 10 pL piezo driven drop-on-demand printhead showing stable droplet formation. Solid films on glass are formed using a drop-by-drop printing strategy. Layer-by-Layer strategy gives best results on polycarbonate substrates forming porous polyurethane structures. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46977.     

Inkjet printing of polyimide insulators for the 3D printing of dielectric materials for microelectronic applications

In this article, we report the first continuous fabrication of inkjet‐printed polyimide films, which were used as insulating layers for the production of capacitors. The polyimide ink was prepared from its precursor poly(amic) acid, and directly printed on to a hot substrate (at around 160 °C) to initialize a rapid thermal imidization. By carefully adjusting the substrate temperature, droplet spacing, droplet velocity, and other printing parameters, polyimide films with good surface morphologies were printed between two conducting layers to fabricate capacitors. In this work, the highest capacitance value, 2.82 ± 0.64 nF, was achieved by capacitors (10 mm × 10 mm) with polyimide insulating layers thinner than 1 μm, suggesting that the polyimide inkjet printing approach is an efficient way for producing dielectric components of microelectronic devices. © 2016 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43361.     

Inkjet printing of polylactic acid on substrates prepared by fused deposition modeling and its potential for selective surface finishing

Fused deposition modeling (FDM) is an additive manufacturing technology commonly used for prototyping. One limiting aspect for the use in functional prototyping and small‐lot production is the achievable surface roughness. The aim of this work was to investigate a potential method of processing polylactic acid (PLA), as it is commonly used for FDM printing, via inkjet technology. PLA solvent inks with different concentrations were prepared by dissolving PLA in 1,4‐dioxane. The tested PLA substrates were prepared by FDM with different layer thicknesses and the change in surface roughness after multilayer inkjet printing was measured by a stylus profilometer. The surface roughness was reduced by up to 50% and further increasing the number of inkjet layers caused voids and PLA accumulations. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43527.     

Inkjet printing of polyvinyl alcohol multilayers for additive manufacturing applications

Here we demonstrate that inkjet printing technology is capable of producing polyvinyl alcohol (PVOH) multilayer structures. PVOH water‐based inks were formulated with the addition of additives such as humectant and pigments. The intrinsic properties of the inks, such as surface tension, rheological behavior, pH, wetting, and time stability were investigated. The ink's surface tension was in the range 30–40 mN/m. All formulated inks displayed a pseudoplastic (non‐Newtonian shear thinning and thixotropic) behavior at low‐shear rates and a Newtonian behavior at high‐shear rates; were neutral solutions (pH7) and demonstrated a good time stability. A proprietary 3D inkjet printing system was utilized to print polymer multilayer structures. The morphology, surface profile, and the thickness uniformity of inkjet printed multilayers were evaluated by optical microscopy and FT‐IR microscopy. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43572.     

Effect of oxygen on the crosslinking and mechanical properties of a thermoset formed by free‐radical photocuring

In this article, we report on the formation of optically transparent photopolymer films from hexanediol diacrylate (HDDA) by inkjet printing, where droplets of monomer approximately 5 μm in diameter were deposited onto a surface. The films were cured by irradiation with a UV‐light‐emitting‐diode light source. It was found that the inkjet‐printed HDDA films picked up a considerable amount of absorbed O₂ during printing. Exposure to increasing amounts of O₂ during photocuring severely restricted both the degree of conversion and the UV dose required for gelation in proportion to the O₂ concentration. Viscoelastic property data indicated that exposure to reduced oxygen concentrations during thermal postcuring (dark reaction) resulted in linear trends of increasing modulus above the glass‐transition temperature (T_g) and increasing T_g itself. Thus, the final crosslink density was greater in fully cured samples that were exposed to atmospheres with increasing inert gas concentrations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Water-based poly(2-ethylhexyl acrylate-itaconic acid) removable adhesives with frost resistance for digital inkjet printing

Adhesives are nonmetallic materials used to bond each layer in many applications for its flexibility. For digital inkjet printing, the requirements of adhesives performance are demanding as they must be able to adhere well to adherend, be removable without leaving adhesive residue, or even causing any damage. Water-based polyacrylates have been widely used for backing adhesive layer in application of digital inkjet printing, due to their various advantages. While the application has been limited on account of the weak frost resistance of common polyacrylates, which could not be used directly under low temperature storage. To improve the weak frost resistance, water-based poly(2-ethylhexyl acrylate-itaconic acid) was synthesized. Itaconic acid (ITA) could be greatly beneficial to improve the frost resistance. The polyacrylates could still be used directly, even after being frozen below at −18°C for 16 hr. The adhesion properties of polyacrylates could also be enhanced by moderate ITA. The results show that the optimal amount of ITA was 2 mass%. The overall properties of the resulting polyacrylates with the 180° peel strength of 2.73 N/25 mm, the tack of 23 #, and the shear holding power of more than 24 hr are suitable for practical applications on removable adhesives for digital inkjet printing.     

Synthesis of UV and thermal dual curing oligomer for solder resist ink using ink-jet printing

A novel solder resist ink for inkjet printing containing the ultraviolet (UV) and thermal dual curing oligomer is introduced in this work. Three kinds of acrylic monomers for the synthesis of the oligomer are successful prepared and their structures are determined by Fourier transfer infrared. Both UV curing process and thermostability are monitored under UV differential scanning calorimetry and thermogravimetric analysis. For the photoreaction process, the oligomer using Lauryl methacrylate as the material of copolymerization possesses the highest reactivity and conversion of carbon–carbon double bond. Besides, this kind of oligomer also owns excellent thermostability, just losing 5.9% of its weight at 288 °C. The solder resist inks containing the oligomers and jetting by the inkjet printer are tested with the adhesion, soldering resistance, and other performances, presenting the outstanding heat resistance and wide application prospects. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47428.     

Photoinitiator-free photopolymerization of acrylate-bismaleimide mixtures and their application for inkjet printing

There is growing interest in using photoinitiator-free systems in coating applications such as inkjet-printing, because residual photoinitiator can alter the properties of the resulting polymer. Bismaleimides (BMI) offer the opportunity to polymerize acrylates without the addition of photoinitiators, as this class of molecules can serve both as polymerizable monomer and as photoinitiator together with electron donor systems, like vinyl ether monomers or acrylates. The UV-induced copolymerization of a low-molecular-weight BMI with various acrylate monomers and oligomers without any photoinitiator was characterized. The BMI-acrylate systems show comparable polymerization speeds to widely used acrylic systems with photoinitiator. Superior thermal stability as well as thermomechanical properties are achieved by enhancing acrylics with BMI. Such photoinitiator-free systems lend themselves to be used for low-migration coatings as well as for high-temperature applications. Here, a characterization of selected BMI-acrylate mixtures regarding their photocuring kinetics and their application as inks for inkjet printing is shown. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47789.     

Digital printing of acrylic fabric with cationic dyes using conventional inkjet printer

A special printing ink formulation based on cationic dyes is developed for digital printing of acrylic fabrics using a conventional inkjet printer. In order to investigate the contribution of color gamut boundary of printer colorants to printing efficiency, customized color targets containing 3164 color patches in 25 different hues were generated. The printed color patches were then fixed through steaming for 30 minutes followed by washing with hot soap and water and finally drying. To show the influence of dye fixation on colorimetric changes as well as color gamut boundary of samples, the L*a*b* values of color patches before and after fixation process were compared. Results demonstrate that color saturation of samples is enhanced dramatically after the dye fixation process. In fact, 3D color gamut of color patches has been drastically expanded as a direct consequence of adsorption to absorption transition. Additionally, dye fixation changes the structure of printed image from halftone superimposed dots to contone superimposed dyes. Strictly speaking, during fixation process, colors inside the halftone dots diffuse through the interfacial area to make the individual printed dots integrated. This is in analogy to the chromogenic photography films and dye‐sublimation thermal transfer processes by which contone images are produced. Moreover, dye fixation improves the washing fastness of digitally printed acrylic fabrics to the level comparable with the traditional screen printing method. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 244–249, 2017     

Improved thin film stability of differently formulated,printed, and crosslinked polymer layers against successive solvent printing

Interface control remains a top challenge of solution-processed organic light emitting diodes (OLED) stacks since the device performance heavily relies on it. Film stability of an inkjet deposited and crosslinked layer against subsequent exposure to a suitable inkjet printed solvent has been investigated. Impact of processing solvent (solvent used to prepare the polymer layer) on solution-cast thin film properties has already been shown for polymer films. To our knowledge, this study is the first one analyzing thin films stability against solvent exposure using technology relevant materials processed via inkjet printing (IJP). The outcome of this research showed that the stability of the crosslinked films is affected by the solvent used for ink formulation. These findings are of great interest for multilayered semiconductors devices, such as OLEDs, field-effect transistors and dye-sensitized solar cells. Differential scanning calorimetry (DSC) was used to quantify the efficiency of the polymer crosslinking reaction in pure powder and in thin films, as processed from different solvents. Crosslinking efficiency measured by DSC correlated well with the deformation induced by the solvent and observed on layer surfaces. The interaction in solution between polymer and solvent has also been evaluated to explain its impact on thin film stability against successive solvent printing. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48895.     

Two-component modified polyurethane sealant for insulating glass: Design,preparation, and application

A new two-component modified polyurethane (PU) sealant was designed and synthesized for insulating glass. This sealant was designed based on a crosslinked reaction between a p-chlorophenol-blocked PU pre-polymer (Pre-polymer 2 ) in Component A and a poly-functional hyperbranched polyamine polymer (polyamide resin 300^#) in Component B. During the synthesis of Pre-polymer 2 , Fourier transform infrared spectral analysis was used to track the process, and the optimal reaction time and temperature were 1.5 h and 80 °C, in the presence of 4, 4′-diphenylmethane diisocyanate (MDI). Different curing agents also used as deblocking agents were screened and it was found that polyamide resin 300^# was a good candidate for the curing reaction. In addition, the low-temperature curing rate was also improved by using dibutyltin dilaurate (DBTDL) and organobentonite together as a composite catalyst. Finally, the prepared two-component modified PU sealant for insulating glass was successfully used in an assembly line with good performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48219.     

Application of a thin intermediate cathode layer prepared by inkjet printing for SOFCs

The application of an inkjet printing process for fabricating solid oxide fuel cell (SOFC) cathodes was investigated. Stably-dispersed LSCF–GDC inks were prepared by ball milling, and the composition was easily controlled by the preparation process. Fabrication of an LSCF–GDC layer was successfully carried out by depositing dots and the thickness was easily controlled by repeating printing process. A planar SOFC single cell with a double-layered cathode (comprised of a paste painted cathode layer and an inkjet printed interlayer) achieved a maximum power density of 0.71 W/cm² at 600 °C. This is the preliminary work for fabricating the cathode layer of a SOFC single cell via inkjet printing.     

Polyurethane dispersions derived from polycarbonatediols and m‐di(2‐isocyanatopropyl)benzene

Aqueous polyurethane dispersions derived from various polycarbonatediols, m‐di(2‐isocyanatopropyl)benzene(TMXDI), and various carboxylic diols including dimethylol propionic acid (DMPA), dimethylol butyric acid (DMBA), and a carboxylic polycaprolactonediol (Placcel 205BA) were prepared by a method in which the dispersing procedure was modified to enhance the molecular weight. The NH₂/NCO ratio during chain extension affected the molecular weight of the polyurethanes, significantly, and an optimum ratio of 0.67:1.0 was used. The molecular weight, particle size, tensile properties, and thermal properties of the polyurethane dispersions were investigated. The effect chemical structure of the polycarbonatediols on the properties shows no obvious trend, but the polyurethane dispersions derived from the carboxylic polycaprolactonediol exhibit smaller particle size and softer tensile properties when compared with those derived from DMPA and DMBA. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Starch‐g‐polycaprolactone copolymerization using diisocyanate intermediates and thermal characteristics of the copolymers

Starch‐g‐polycaprolactone copolymers were prepared by two‐step reactions. The diisocyanate‐terminated polycaprolactone (NCO–PCL) was prepared by introducing NCO on both hydroxyl ends of PCL using diisocyanates (DI) at a molar ratio between PCL and DI of 2:3. Then, the NCO–PCL was grafted onto corn starch at a weight ratio between starch and NCO–PCL of 2:1. The chemical structure of NCO–PCL and the starch‐g‐PCL copolymers were confirmed by using FTIR and ¹³C‐NMR spectrometers, and then the thermal characteristics of the copolymers were investigated by DSC and TGA. By introducing NCO to PCL (M_n : 1250), the melting temperature (T_m ) was reduced from 58 to 45°C. In addition, by grafting the NCO–PCL (35–38%) prepared with 2,4‐tolylene diisocyanate (TDI) or 4,4‐diphenylmethane diisocyanate (MDI) onto starch, the glass transition temperatures (T_g 's) of the copolymers were both 238°C. With hexamethylene diisocyanate (HDI), however, T_g was found to be 195°C. The initial thermal degradation temperature of the starch‐g‐PCL copolymers were higher than that of unreacted starch (320 versus 290°C) when MDI was used, whereas the copolymers prepared with TDI or HDI underwent little change. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 986–993, 2000     

Color management for enhancing the performance of superfine nylon ink jet printing with reactive dyes inks

The challenge for the inkjet printing textiles is that the colors reproduction quality of printed output is an accurate match to the original artwork. Actual evidence from art workers with digital print facilities reveals that they regularly encounter problems in this area. This article concerns the initial stages of an investigation into color accuracy in digitally printed superfine nylon under low temperature plasma pretreatment in order to get a accuracy and color‐increased superfine nylon digital prints. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 346–351, 2017     

Recycling of ultrahigh molecular weight polyethylene waste used for preparing high performance synthetic paper

Due to their widespread applications, the production and consumption of plastics have increased sharply and also brought about a lot of waste. However, only one‐fourth of plastic solid waste is effectively recycled, and the rest is almost entirely disposed in landfills. In this article, high performance synthetic paper used for printing was successfully prepared from ultrahigh molecular weight polyethylene waste adopting thermally induced phase separation method. Silicon dioxide was added as filler and mineral oil was used as diluent. Whiteness, chemical resistance, tensile strength, thermal stability, surface morphology, and inkjet print of synthetic paper was investigated, respectively. It is indicated that the resulting synthetic paper possesses excellent printing effect. Its whiteness equally distributes around 80% and the highest tensile strength is up to 5.5 MPa. They also reveal good resistance to chemical corrosion and have good shape maintenance. As a result, the preparation of high performance synthetic paper for industrial applicability is expected to perform by recycling plastics waste. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44159.     

Synthesis and characterization of polyhydroxylated polybutadiene binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) with isophorone diisocyanate

A macromolecular hindered phenol antioxidant, polyhydroxylated polybutadiene containing thioether binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (PHPBT‐b‐TPH), was synthesized via a two‐step nucleophilic addition reaction using isophorone diisocyanate (IPDI) as linkage. First, the ? OH groups of PHPBT reacted with secondary ? NCO groups of IPDI to form the adduct PHPBT‐NCO, then the PHPBT‐b‐TPH was obtained by one phenolic ? OH of 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (TPH) reacting with the PHPBT‐NCO. The PHPBT‐b‐TPH was characterized by Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance (¹H‐NMR), ¹³C‐NMR, and thermogravimetric analysis, and its antioxidant activity in natural rubber was studied by an accelerated aging test. Influences of reaction conditions on the two nucleophilic reactions between ? OH group and ? NCO group were investigated. In addition, catalytic mechanism for the reaction between PHPBT‐NCO and TPH was discussed. The results showed that the adduct PHPBT‐NCO could be obtained by using dibutyltin dilaurate (DBTDL) as catalyst, and the suitable temperature and DBTDL amount were 35°C and 3 wt %, respectively. However, triethylamine (TEA) was more efficient than DBTDL to catalyze the reaction between PHPBT‐NCO and TPH because of steric hindrance effect. In addition, it was found that the thermal stability and antioxidant activity of PHPBT‐b‐TPH were higher than those of the low molecular weight antioxidant TPH. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40942.     

Anisotropy of poly(lactic acid)/carbon fiber composites prepared by fused deposition modeling

It is well known that 3D printed parts prepared by fused deposition modeling (FDM) exhibit large anisotropy of mechanical properties. In this article, poly(lactic acid; PLA)/carbon fiber (CF) composites with different built orientations (X, Y, Z) were prepared by FDM. The effects of printing temperature, speed, orientations, and layer thickness on the mechanical properties of the composites were systematically investigated. The mechanical properties of PLA/CF composites show more significant anisotropy. The orientation of the fibers along the printing direction is displayed by scanning electron microscopy. Printing parameters bring almost no effect on mechanical properties of the X-construct oriented specimen, and bring obvious effect on those of the Y-construct oriented specimen and Z-construct oriented specimen. According to the analysis, carbon fiber can amplify this anisotropy from layer fashion, and the key factors from printing parameters are porosity and bond strength between fuses. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48786.     

Yellow resistant photosensitive resin for digital light processing 3D printing

Digital light processing (DLP) has been studied and developed in the field of three-dimensional (3D) printing in recent years due to its fast curing rate and high resolution. To reduce the cost and viscosity of the resin system, the aromatic polyurethane acrylates (PUAs) were used as oligomer. The matrix resin called PUH₂ consists of oligomers (PUA, bisphenol A polyoxyethylene ether dimethyl acrylate) and active diluents (hydroxyethyl acrylate, hydroxyethyl methacrylate). However, the photosensitive resin containing aromatic isocyanate groups was easily yellowed under ultraviolet light. In this article, we developed a resin for DLP 3D printing with yellowing resistance, excellent mechanical properties and high heat resistance. The optimal ratio of 3DP-PUH₂ resin was PUH₂/TPO/RYOJI-292/dye/nanosilica = 100/5/0.4/0.01/0.1, and its viscosity was 500 cp, which is suitable for DLP 3D printing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48369.     

Study on cross-linking agent of a novel one-component API adhesive

The high reactivity and toxicity of isocyanates do not allow their storage and use in one-component system aqueous polymer isocyanate adhesives. Blocked isocyanates are a solution to protect the isocyanate groups by blocking with suitable blocking agent. In order to obtain eco-friendly systems and eliminate the effect of the organic solvents on environment, the blocked isocyanates can be dispersed in water by using external emulsifier by incorporating hydrophilic groups into the backbone. In this work, a series of waterborne blocked polyisocyanate dispersions were prepared by anionic modified process, using polyaryl polyisocyanate (PAPI), 2,4,6-trichlorophenol (TCP), and dimethylol propionic acid. Particle sizes were measured and compared by laser particle sizer and scanning electron microscopy. The structures of aqueous dispersions were characterized by FTIR, ¹H NMR, and ¹³C NMR, and results confirmed that the –NCO groups are effectively blocked by –OH groups. Thermal property was investigated using differential scanning calorimetry; then, kinetic parameters, ΔE, and n were deduced. It was found that the deblocking temperature of aqueous dispersion is about 55?°C. Hydrophilicity was characterized by measuring the water contact angles. The experimental results showed that the contact angle of solvent-borne solution is 68.6°, while that of aqueous dispersion is only 25.2°, which indicated that the hydrophilicity of waterborne TCP-blocked PAPI increases for the introduced hydrophilic group compared with solvent-borne TCP-blocked PAPI. The compressive shear strength was tested to evaluate wood bonding performance of the adhesive.