UV-curable Polyurethane Acrylate Research Articles

Synthesis and characterization of ureidopyrimidinone-functionalized polyurethane acrylates and their hybrid nanocomposites for UV coating applications

AbstractIn this study, ureidopyrimidinone moieties (UPy), capable of physical crosslinking via quadruple hydrogen bonding, were successfully incorporated into UV-curable polyurethane acrylate prepolymers. First, a hydroxyl-terminated unsaturated ester monomer was synthesized and reacted with isophorone diisocyanate to create a hydroxyl-terminated UV-curable urethane oligomer (U–OH). Then, isocyanate-terminated building blocks (UPy moieties and an acrylate-based photosensitive monomer) were synthesized and used in various ratios to functionalize U–OH for the preparation of a series of UV-curable UPy-containing polyurethane acrylate (PUA) resins. The resulting products were structurally characterized using 1H NMR and FTIR spectroscopy. Furthermore, organic–inorganic hybrid nanocomposites were obtained by introducing silane coupling agents into PUA resins using the sol–gel process. A series of UV-curable UPy-containing PUA coatings and hybrid nanocomposites were prepared, and their synergistic effect on coating properties was investigated. The dynamic mechanical analysis revealed that the Tg of the samples increased with increasing UPy content, although the mechanical properties remained largely unaltered, as shown by the stress–strain test. The studies also demonstrated that the hybrid nanocomposites exhibited higher decomposition temperatures and better thermal stability compared to pure PUAs. All the coatings exhibited good transparency in the visible region. An optical microscope was used to investigate the self-healing property by scratching the plexiglass panels with a razor blade. Among the other samples, the coating with the highest percentage of UPy content exhibited the best self-healing ability after heat treatment at 90 °C for 10 min. Graphical abstract

Biomimetic design of micro- and nano-wrinkle wood surface via coating reinforced with hyperbranched polymer grafted cellulose nanofibers for skin-tactile performance

Inspired from human skin, micro- and nano-wrinkled wood surface with skin-tactile performance was designed and developed using a waterborne UV-curable polyurethane acrylate coating and cellulose nofibers (CNF). To further improve the properties, the CNF was diacetylated to D-CNF and further grafted with a hyperbranched polymer containing rich end amino groups (HB-CNF). The surface structure and chemical reactions were characterized, and the skin-tactile performance of the coating was comprehensively investigated. The HB-CNF exhibited excellent dispersion in the coating, and extensive reactions occurred between the two through the –NH2 and terminal –NCO groups, resulting in much improved mechanical properties and durability. Micro-wrinkles with a width of approximately 12–15 μm and a height of 8–14 μm were created, and nano-protrusions of wrinkles ranging from to 50–100 nm were obtained. The coated surface was hydrophobic and exhibited high resilience after compression, with a gloss of 3.3 GU at an incident angle of 60° and a static friction coefficient of 0.26, both of which were similar to those of human skin. The results presented an effective strategy for high-performance wood products with a good feeling, which is helpful to improve the market competitiveness and meet the people's pursuit of a better life.

A study on the fabrication of metal microneedle array electrodes for ECG detection based on low melting point Bi–In–Sn alloys

This study describes the fabrication and characteristics of microneedle array electrodes (MAEs) using Bismuth–Indium–Tin (Bi–In–Sn) alloys. The MAEs consist of 57 pyramid-shaped needles measuring 340 μm wide and 800 μm high. The fabrication process involved micromolding the alloys in a vacuum environment. Physical tests demonstrated that Bi–In–Sn MAEs have good mechanical strength, indicating their suitability for successful skin penetration. The electrode–skin interface impedance test confirmed that Bi–In–Sn MAEs successfully penetrated the skin. Impedance measurements revealed the importance of insulating the microneedle electrodes for optimal electrical performance, and a UV-curable Polyurethane Acrylate coating was applied to enhance insulation. Electrocardiogram measurements using the Bi–In–Sn MAEs demonstrated performance comparable to that of traditional Ag/AgCl electrodes, which shows promise for accurate data collection. Overall, the study demonstrates successful, minimally-invasive skin insertion, improved electrical insulation, and potential applications of Bi–In–Sn microneedle array. These findings contribute to advancements in microneedle technology for biomedical applications.

Effect of Photoinitiator Concentration and Film Thickness on the Properties of UV-Curable Self-Matting Coating for Wood-Based Panels

Matte coatings have found wide-ranging applications across diverse industries. In this study, self-matting films with surface wrinkles were produced by exposing UV-curable polyurethane acrylate (UV-WPUA) resin to 172 nm Xe2* excimer and medium-pressure mercury lamps. The gloss values, micromorphologies, water contact angles (WCAs), roughness values, and friction behaviors of UV-WPUA films with different photoinitiator (PI) concentrations and thickness were investigated for the first time. The results indicate that the gloss values of the films at the same thickness enhance with the increase of PI concentration, while the amplitude of wrinkles, roughness, and WCAs decrease; however, the friction coefficient shows insignificant variations. While the PI concentration is unchanged, an increase in film thickness results in a decrease in gloss value and an increase in roughness and friction coefficient. Nevertheless, the WCA is relatively constant. The PI concentration of 0.5 wt% (lowest gloss value of cured film) was utilized to prepare the UV-WPUA wood coating. The cured coating film exhibited low gloss (4.9 GU at 60° and 5.2 GU at 85°) and outstanding mechanical properties, including 3H pencil hardness, grade 0 adhesion, excellent wear resistance, and tensile property. These findings can be utilized to guide the development of self-matting wood coatings and the production of wood-based panels used in industrial finishing.

3D printing polyurethane acrylate(PUA) based elastomer and its mechanical behavior

Liquid-crystal display(LCD) 3D printing, also known as light during 3D printing or photopolymer 3D printing, is a type of additive manufacturing technology that uses light-sensitive resin to create three-dimensional objects. This technology has gained popularity in recent years owing to its ability to create high-resolution, detailed objects with a wide range of materials, including shape-memory polymers, toughness resins, and elastomers. Elastomers are a type of polymer material that has the ability to stretch and deform under an applied force, but return to their original shape when the force is removed. The superior deformation recovery rate contributes to elastomer use in various industries, including automotive, aerospace, medical, and consumer goods. In this study, a UV-curable polyurethane acrylate(PUA) elastomer with an elongation of 100%–200% was developed. Using LCD 3D printing, we were able to fabricate Triply periodic minimal surface(TPMS) lattice structures with this elastomer investigated the compressive behavior of TPMS structures with different compressive ratios of 20%–50%. Our results demonstrate that this approach enables the creation of flexible energy-absorbing structures under cyclic loading. This study highlights the potential of LCD 3D printing technology for the production of elastomeric materials with tunable mechanical properties.

UV-Curable Polyurethane Acrylate Pressure-Sensitive Adhesives with High Optical Clarity for Full Lamination of TFT-LCD

Optically clear pressure-sensitive adhesives (PSAs) face the challenges presented by a range of electronic and touch screen applications. Although many efforts have been made to manipulate the optical and adhesion properties of ultraviolet (UV)-curable acrylate-based PSAs, further application and large-scale production are still limited owing to the intrinsically poor processability that stems from the large content of the high-vinyl-equivalent and low-viscosity acrylic monomers. Introducing a low-vinyl-equivalent and high-viscosity polyurethane acrylate (PUA) prepolymer into the formulation is a facile method to solve this issue without sacrificing the transparency. In this study, a series of PUA prepolymers are prepared to construct the model of PUA-co-2-ethylhexyl acrylate (2EHA), denoted as poly(PUA-2EHA). The influence of PUA prepolymer architectures (average functionality and molecular features) on the optical and adhesion properties is elaborately discussed. The chemical cross-linking-induced enhancement of the haze values of PUA-based PSAs is investigated for the first time. Moreover, an improved and uniform bright image display without blemish, which is usually called the Mura defect-free image display in the industrial field, is obtained by using poly(PUA-2EHA) as the optically clear adhesive for full lamination of the thin-film transistor liquid crystal display (TFT-LCD) module. The laminated TFT-LCD module could be disassembled easily without leaving the residue on the screen. These results provide clear design guidelines to regulate the properties of PUA-based PSAs, which are especially valuable for the large-scale industrial production of UV-cured PSAs and facilitate the development of display technologies.

Study on Press Formability and Properties of UV-Curable Polyurethane Acrylate Coatings with Different Reactive Diluents.

UV-curable coatings have numerous advantages, including environmental sustainability due to 100% solid content, economic feasibility attributable to relatively fast curing time, decent appearance, mechanical properties, chemical resistance, and abrasion resistance. However, UV-curable polyurethane acrylate coatings on metals apparently restrict their engineering applications owing to low mechanical properties and poor thermal stability, giving UV-curable coatings less flexibility and formability. In this study, we evaluated the property change of films according to the type of reactive diluents that lowers the viscosity of UV-curing coatings for pre-coated metal and has a substantial effect on the curing rate, viscoelastic properties, adhesive properties, and flexibility of the film. Moreover, there are many changes in the properties of coatings according to varied curing conditions in order to evaluate the oxygen inhibition phenomenon during the curing process in the atmosphere. In particular, to evaluate the effect of reactive diluents on forming formability, which is the most crucial property for the pre-coated metal, this study used conventional formability tests, such as t-bending or the Erichsen test. Moreover, a cross-die cup drawing mold with a similar form as failure and Safety Zone was utilized in order to obtain clearer information on its actual formability. The analysis on the effect of failure and safety zone on the material used in press forming was conducted by assessing limit punch height and forming a limit diagram of the manufactured film according to varied reactive diluents.

Bio-based upcycling of poly(ethylene terephthalate) waste to UV-curable polyurethane acrylate

A strategy for upcycling poly(ethylene terephthalate) into a high-value UV-curable polyurethane acrylate coating using bio-based cardanol diol as a glycolysis agent.

Robust UV-curable polyurethane acrylate coating

Robust UV-curable polyurethane acrylate coating

UV curable PUA ink with polymerizable surfactant-enhanced Ag@PPy for fabricating flexible and durable conductive coating on the surface of cotton fabric

In this study, a stable silver@polypyrrole (Ag@PPy) composite was prepared with the help of sodium dodecyl sulfate (SDS) and polymerizable surfactant ammonium allyloxynonylphenol ethoxylate (DNS-86). It was then combined with polyurethane acrylate (PUA) to prepare a conductive ink and applied on the surface of cotton fabric. By an energy-saving and sustainable UV curing method, the ink was effectively fixed to fabricate flexible and durable textile. The effects of DNS-86 on the properties of Ag@PPy composite were investigated and the results showed that DNS-86 could reduce its size, make its distribution more uniform and improve its stability. Then, the effects of DNS-86 on the performance of conductive coating on fabric were analyzed by measuring the resistance and water contact angle, revealing that DNS-86 could participate in the UV film-forming reaction of PUA molecules, so as to optimize the film structure for higher conductivity. Finally, the effect of DNS-86 on the flexibility and durability of conductive coating were evaluated. The results indicated that DNS-86 could improve the structural integrity and toughness of PUA film, enhance the adhesion between conductive coating and cotton surface, and make it more resistant to various environmental erosions.

Fast Curing Multifunctional Tissue Adhesives of Sericin-Based Polyurethane-Acrylates for Sternal Closure.

The use of wire cerclage after sternal closure is the standard method because of its rigidity and strength. Despite this, they have many disadvantages such as tissue trauma, operator-induced failures, and the risk of infection. To avoid complications during sternotomy and promote tissue regeneration, tissue adhesives should be used in post-surgical treatment. Here, we report a highly biocompatible, biomimetic, biodegradable, antibacterial, and UV-curable polyurethane-acrylate (PU-A) tissue adhesive for sternal closure as a supportive to wire cerclage. In the study, PU-As were synthesized with variable biocompatible monomers, such as silk sericin, polyethylene glycol, dopamine, and an aliphatic isocyanate 4,4′-methylenebis(cyclohexyl isocyanate). The highest adhesion strength was found to be 4322 kPa, and the ex vivo compressive test result was determined as 715 kPa. The adhesive was determined to be highly biocompatible (on L-929 cells), biodegradable, and antibacterial (on Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus bacteria). Finally, after opening the sternum of rats, the adhesive was applied to bond the bones and cured with UV for 5 min. According to the results, there was no visible inflammation in the adhesive groups, while some animals had high inflammation in the cyanoacrylate and wire cerclage groups. These results indicate that the adhesive may be suitable for sternal fixation by preventing the disadvantages of the steel wires and promoting tissue healing.

Combustion behavior of end-sealed nitroamine propellant by photocurable composite deterrents

In this work, energetic composite composed of UV curable polyurethane acrylate and RDX was used as deterrent coating for 19-perforated nitroamine propellants plasticized by nitroglycerin and 1, 5-diazido-3-nitrazpentane (DIANP). The nitroamine propellant was end-sealed with the photocurable energetic composite material by using spraying and UV curing method. Combustion behaviors including burning progressivity and temperature sensitivity were studied by performing closed bomb test on propellants with 0.74%, 1.01% and 1.15% deterrent. The inner structure detection revealed that the deterrent penetrated into the perforations during coating process. The end-sealed propellant with blocked perforations exhibited inhibition of initial gas generation rate, which was demonstrated by dynamic vivacity curves. It is inspiring that the propellants coated with 1.01% and 1.15% deterrent presented excellent consistency according to the dynamic vivacity curves between 20 °C and 50 °C. Moreover. it can be indicated that the plugs in perforations conduced to temperature independence property of propellant under ambient temperature. This benefit contributes to improvement of the firing safety at high temperatures.

Biomimetic Rose Petal Structures Obtained Using UV-Nanoimprint Lithography.

This study aims to produce a hydrophobic polymer film by mimicking the hierarchical micro/nanostructures found on the surface of rose petals. A simple and two-step UV-based nanoimprint lithography was used to copy rose petal structures on the surface of a polyurethane acrylate (PUA) film. In the first step, the rose petal was used as a template, and its negative replica was fabricated on a commercial UV-curable polymer film. Following this, the negative replica was used as a stamp to produce rose petal mimetic structures on UV curable PUA film. The presence of these structures on PUA influenced the wettability behavior of PUA. Introducing the rose petal mimetic structures led the inherently hydrophilic material to display highly hydrophobic behavior. The neat PUA film showed a contact angle of 65°, while the PUA film with rose petal mimetic structures showed a contact angle of 138°. Similar to natural materials, PUA with rose petal mimetic structures also displayed the water pinning effect. The water droplet was shown to have adhered to the surface of PUA even when the surface was turned upside down.

Controllable fabrication of silver-deposited polyurethane acrylate nanopillar array film as a flexible surface-enhanced Raman scattering (SERS) substrate with high sensitivity and reproducibility.

Acontrollable method for fabricating flexible surface-enhanced Raman scattering (SERS) substrates is demonstratedby depositing silver onto a flexible nanopillar array film. The flexible nanopillar array film was cost-effectively prepared by replicating an anodic aluminum oxide (AAO) template with UV-curable polyurethane acrylate (PUA) over a large area. Then, the deposition of silver was done by an Ar-assisted thermal evaporation. In the deposition process, the partial pressure of Ar was optimized because it has a significant influence on the SERS intensity through the microstructural changes of silver deposited on PUA nanopillars. In addition, the increase in the nanopillar diameter and height enhanced the SERS intensity obtained at 785-nm excitation because of the increased number of hot spots. However, the agglomeration of Ag-deposited nanopillars, which is caused by high aspect ratios, negatively affected the SERS performance in terms of intensity and standard deviation. The optimized Ag-deposited nanopillar array film with nanopillar diameters and heights of 80nm and 200nm exhibited excellent SERS sensitivity and signal reproducibility with stable mechanical flexibility. For application in food and biomedical analysis, it was used for detecting saccharin and peptide and showed a good linear relationship between the SERS intensity and concentration. These findings demonstrate the suitability of our method for the controllable fabrication and optimization of flexible SERS substrates with high sensitivity and reproducibility.

A novel polymer-based nitrocellulose platform for implementing a multiplexed microfluidic paper-based enzyme-linked immunosorbent assay

Nitrocellulose (NC) membranes, as porous paper-like substrates with high protein-binding capabilities, are very popular in the field of point-of-care immunoassays. However, generating robust hydrophobic structures in NC membranes to fabricate microfluidic paper-based analytical devices (μPADs) remains a great challenge. At present, the main method relies on an expensive wax printer. In addition, NC membranes very easy to adhere during the printing process due to electrostatic adsorption. Herein, we developed a facile, fast and low-cost strategy to fabricate μPADs in NC membranes by screen-printing polyurethane acrylate (PUA) as a barrier material for defining flow channels and reaction zones. Moreover, hydrophobic barriers based on UV-curable PUA can resist various surfactant solutions and organic solvents that are generally used in immunoassays and biochemical reactions. To validate the feasibility of this PUA-based NC membrane for immunoassays in point-of-care testing (POCT), we further designed and assembled a rotational paper-based analytical device for implementing a multiplexed enzyme-linked immunosorbent assay (ELISA) in a simple manner. Using the proposed device under the optimal conditions, alpha fetoprotein (AFP) and carcinoembryonic antigen (CEA) could be identified, with limits of detection of 136 pg/mL and 174 pg/mL, respectively, which are below the threshold values of these two cancer biomarkers for clinical diagnosis. We believe that this reliable device provides a promising platform for the diagnosis of disease based on ELISA or other related bioassays in limited settings or remote regions.

Amphiphilic alginate stabilized UV-curable polyurethane acrylate as a surface coating to improve the anti-wrinkle performance of cotton fabrics

In this paper, a reactive amphiphilic alginate was prepared by an Ugi reaction using 4,4′-diaminostilbene-2,2′-disulfonic acid and its structure was analyzed by FT-IR and 1H NMR measurement. Subsequently, it was utilized as emulsifier to prepare polyurethane acrylate (PUA) emulsion and the colloidal properties including zeta potential, droplet size distribution and stability were evaluated. The results showed that the PUA emulsion by this modified alginate had better colloidal stability than that by original one. Finally, stable PUA emulsion was used for surface treatment of cotton fabrics in a UV curing process to improve their anti-wrinkle performance. By measuring the wrinkle recovery angle, it was found the anti-wrinkle properties of cotton fabrics were significantly improved with the increase in the amount of modified alginate. In addition, this anti-wrinkle finishing method was found to have many advantages such as low temperature, low yellowing as well as high washing resistance.

Improving mechanical and water vapor barrier properties of the parylene C film by UV-curable polyurethane acrylate coating

Abstract Parylene C (PC) films have been widely used in many fields, such as metal anti-corrosion, electronic packaging, etc. However, the relatively poor mechanical properties and the deteriorated water barrier performance due to the easy fracture under external stress have restricted their application. It is a relatively simple and good method to maintain the water vapor barrier and enhance the mechanical properties of PC film by covering a flexible coating on its surface. In this work, a new polyurethane acrylate (PUA) coating was prepared and coated on the PC film by ultraviolet curing technology to form the PC/PUA composite film. The results showed that the PUA coatings could improve the water vapor barrier and mechanical properties of the PC film simultaneously. The water vapor transmittance rate was reduced from 1.1791 g·(m−2·day−1) of the original PC film to 0.5636 g·(m−2·day−1) of the PC/PUA composite film. The elongation at break and the impact energy were increased to 48.36% and 41.67%, respectively, which would widen the application of PC films in the fields of flexible electronics or smart wear.

Nanopatterned Polymer Molds Using Anodized Aluminum Templates for Anti-Reflective Coatings.

This work introduces a facile geometry-controlled method for the fabrication of embossed and engraved polymeric moth-eye-inspired nanostructures in imprinting molds using anodic aluminum oxide (AAO) templates, resulting in a novel anti-reflective transparent coating. The moth-eye nanostructures are prepared directly on the surface of a flexible polyethylene terephthalate (PET) substrate. As a prerequisite procedure, a UV-curable polyurethane acrylate resin is spun on the PET. The shape of the moth-eye nanostructures can then be adjusted by controlling the size and shape of the nanopores in the AAO templates. Both embossed and concaved polymer moth-eye nanostructures were successfully mounted on a PET substrate. Embossed polymer replica molds were prepared using the AAO master templates in combination with an imprinting process. As revealed by field-emission electron microscope (FE-SEM) images, conical nanopatterns in the AAO template with a diameter of ~90 nm and a depth of ~100 nm, create a homogeneous embossed morphology in the polymer moth-eye nanostructure. The polymeric molds with the depths of 300 and 500 nm revealed the amalgamated structures in their apexes. In addition, a dip-imprinting process of the polymeric layers was implemented to yield a concaved mold by assembly on the surface of the 100 nm embossed polymer mold substrate. Considering that the embossed structures may be crumbled due to their protuberant shapes, the concaved geometries can have an advantage of stability in a certain application concerning physical degradation along with a higher transmission by ~2%, despite somewhat nonuniform structure. The experimental and theoretical results of this study indicate that this polymer layer has the potential for use in anti-reflective coating applications in transparent films.

Rubber Seed Oil-Based UV-Curable Polyurethane Acrylate Resins for Digital Light Processing (DLP) 3D Printing.

Novel UV-curable polyurethane acrylate (PUA) resins were developed from rubber seed oil (RSO). Firstly, hydroxylated rubber seed oil (HRSO) was prepared via an alcoholysis reaction of RSO with glycerol, and then HRSO was reacted with isophorone diisocyanate (IPDI) and hydroxyethyl acrylate (HEA) to produce the RSO-based PUA (RSO-PUA) oligomer. FT-IR and 1H NMR spectra collectively revealed that the obtained RSO-PUA was successfully synthesized, and the calculated C=C functionality of oligomer was 2.27 per fatty acid. Subsequently, a series of UV-curable resins were prepared and their ultimate properties, as well as UV-curing kinetics, were investigated. Notably, the UV-cured materials with 40% trimethylolpropane triacrylate (TMPTA) displayed a tensile strength of 11.7 MPa, an adhesion of 2 grade, a pencil hardness of 3H, a flexibility of 2 mm, and a glass transition temperature up to 109.4 °C. Finally, the optimal resin was used for digital light processing (DLP) 3D printing. The critical exposure energy of RSO-PUA (15.20 mJ/cm2) was lower than a commercial resin. In general, this work offered a simple method to prepare woody plant oil-based high-performance PUA resins that could be applied in the 3D printing industry.

Siloxane-modified waterborne UV-curable polyurethane acrylate coatings: Chemorheology and viscoelastic analyses

The effects of molecular weight of PDMS on chemorheology and viscoelastic behavior of siloxane modified waterborne UV-curable polyurethane acrylate dispersions (Si-WUPAs) were assessed via a photo rheometer as a versatile tool for in situ observation of chemical and mechanical characteristics during photopolymerization reaction. The roles of PDMS soft segment and its Mw on the rheological behavior were examined followed by exploring the flow curves of Si-WUPA system. The viscosity of Si-WUPA samples decreased with increasing shear rate, showing a pseudoplastic behavior for high-molecular-weight PDMS. However, the unmodified sample and specimens containing dual soft segments of PTMG and low Mw of PDMS revealed a Newtonian behavior. The curing process was accomplished using a photoinitiator to induce polymerization of acrylate double bonds at 40 °C and 60 °C, signifying a-three-step curing process. Enhanced drying time and gelation points were observed upon increasing Mw and content of PDMS. Correspondingly, the storage modulus diminished due to incomplete curing because of contribution of more flexible PDMS chains to reaction. Thermomechanical properties of UV-cured Si-WUPAs films were systematically studied via DMTA, revealing two different behaviors depending on the Mw of PDMS. Si-WPUAs systems showed enlarged width of tanδ peak in half of heights unconditionally, suggesting increased incompatibility and non-uniformity of the final film caused by micro-phase separation of PDMS chains. Mechanical properties were also inspected by tensile test confirming the DMTA results. Tensile isotherms of cured Si-WPUA specimens were remarkably sensitive to both Mw and the content of PDMS.