Curable Polyurethane Acrylate Research Articles

Erratum: Effect of Hydrophilic Bentonite as a Filler on Curing Performance of Pigmented UV Curable Polyurethane Acrylate Coating

Erratum: Effect of Hydrophilic Bentonite as a Filler on Curing Performance of Pigmented UV Curable Polyurethane Acrylate Coating

Highly flexible liquid metal/photocurable polymer electrodes via direct laser patterning

A highly flexible electrode was fabricated using eutectic gallium-indium (eGaIn) liquid metal combined with an ultraviolet (UV)-curable polyurethane acrylate (PUA) polymer. The eGaIn liquid metal electrodes prepared by a negative-type direct patterning technique using a UV pulse laser can eliminate the need for complex photolithography masks. The optimal UV pulsed laser peak fluence was ∼1.43 J/cm2 to pattern and sinter the eGaIn/PUA composite electrode simultaneously. The laser-patterned eGaIn/PUA composite electrode under the optimal laser condition exhibited a remarkable electrical conductivity of 6.33 × 105 S/m with a patterning resolution of ∼40 μm. Moreover, the resistance of the electrode only deteriorated by 0.95% after 50,000 cycles of severe cyclic folding at a peak strain of 2.5% with a bending radius of 1 mm, demonstrating its exceptional flexibility and durability. These easily patterned eGaIn flexible electrodes via direct laser patterning techniques hold great promise for applications in wearable and flexible electronic devices that require extreme flexibility.

Castor oil‐based UV‐curable polyurethane acrylate resins for digital light processing (DLP) 3D printing technology

AbstractIn this work, a novel UV‐curable polyurethane acrylate (PUA) oligomer was developed from castor oil (CO). Reaction monitoring and structures of the PUA oligomer were characterized by Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR). Subsequently, a series of UV‐curable resins were prepared by combining PUA with different reactive diluents, and their effect on thermal and mechanical properties was investigated. From the overall characterization trend, it was observed that the formulation containing trimethylolpropane triacrylate (TMPTA) showed the highest mechanical strength and thermal stability. Whereas the formulation containing isobornyl acrylate (IBOA) showed the least performance, and dipropyleneglycol diacrylate (DPGDA) showed properties ranging between TMPTA and IBOA. Furthermore, incorporating 1% TiO2 into the formulation increases the resin's viscosity and mechanical properties without disturbing its thermal stability. This work offered a simple method to prepare vegetable oil‐based high‐performance PUA resins that could be used in the 3D printing industry for general‐purpose prototyping applications to make architectural models, automotive components, and medical components.

Optimizing the Superhydrophobicity of the Composite PDMS/PUA Film Produced by a R2R System

Maintaining the surface of solar cell panels free from contaminants to ensure their efficiency is a time-consuming and tedious task. Therefore, several methods of fabricating artificial transparent superhydrophobic surfaces have been reported to overcome that problem. However, most of the proposed fabrication methods are unscalable due to their complexity. Herein, a facile and cost-effective roll-to-roll system to fabricate a highly flexible and optically transparent polydimethylsiloxane/polyurethane acrylate superhydrophobic (FTPPS) film was proposed. The superhydrophobicity of the film was achieved by the combination of the surface roughness─the ultraviolet curable polyurethane acrylate (PUA) microstructures and the low surface energy material coating─the thin polydimethylsiloxane layer coated on PUA structures using capillary force. The superhydrophobicity of the FTPPS film was carefully optimized using various designs of PUA micro-post and the material properties of the film were examined systematically by different characterization techniques. The highest measured static water contact angle (WCA) of the FTPPS film is 153.3° ± 1.8 and its lowest water sliding angle is ∼9.5° ± 0.2. Moreover, the film still exhibited high WCAs of more than 142° even after being impacted multiple times by an adhesive probe or sand grains. This result demonstrates the high mechanical durability and flexibility of the as-fabricated superhydrophobic film. Finally, the potential application of the film as a protective cover for solar cells was also illustrated through the consistent photovoltaic conversion efficiency of the solar cell module covered by the film compared to that of the uncovered solar panel.

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.

Preparation and Properties of UV and Aziridine Dual–Cured Polyurethane Acrylate Emulsion

For the UV–curable waterborne polyurethane acrylate (WPUA) emulsion, the free carboxylic groups in the molecular chains introduced by hydrophilic monomers are the inherent disadvantage. We prepared UV and aziridine dual–cured WPUA (UV/AZ–WPUA) emulsion that the carboxylic groups can be crosslinked by the trifunctional aziridine crosslinking agent, trimethylolpropane tris(2-methyl-1-aziridinepropionate) (Sac–100). The effects of Sac–100 content on the gel fraction, tensile properties, hardness, wear resistance, water resistance, and surface morphology of the cured films and coatings were investigated. The results show that, with the increase of the Sac–100 content, the gel fraction, tensile strength, elongation at break, and toughness of the films increase first and then decrease and the wear weight loss and water absorption ratio gradually decrease; in addition, Sac–100 also has an effect on the surface roughness of the coatings. Through comprehensive evaluation, it is considered that the optimum Sac–100 content is 4 wt% in UV/AZ–WPUA system. With the optimum Sac–100 content, the gel fraction of the coating film is 89.78 wt%, the tensile strength is 34.58 MPa, the elongation at break is 343.64%, the toughness is 65.08 MJ/m3, the wear loss is 4.7 mg, and the equilibrious water–absorption ratio is 11.63 wt%. Compared with the UV–cured film without Sac–100, the tensile strength, toughness, and hardness of the dual–cured films increase by 155.4%, 129.3%, and 25.7%, respectively, and the water absorption ratio decreases by 27.1%.

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.

Effect of Hydrophilic Bentonite as a Filler on Curing Performance of Pigmented UV Curable Polyurethane Acrylate Coating

The effect of hydrophilic bentonite incorporation on the curing performance of pigmented ultra violet (UV) curable polyurethane acrylate (PUA) coating was investigated. To the best of our knowledge, crock fastness and gloss properties of pigmented bentonite incorporated UV curable PUA coating have been examined for the first time. Fourier Transform Infrared (FTIR) spectroscopy analysis of the cured films showed that addition of both bentonite and pigment decreased the conversion of C=C. However a more significant drop was observed with the addition of pigment into the formulation. The drop of conversion with the incorporation of bentonite did not adversely affect the hardness and crock fastness values and hence the UV curing performance of the films. Bentonite particles were efficiently distributed in the film and intercalation was achieved owing to the ball milling process. Hardness of the cured films increased with the increase in energy levels. On the other hand, hardness decreased at higher pigment concentrations however, was not affected adversely by bentonite incorporation. Gloss was found to be enhanced with the addition of bentonite in both pigmented and unpigmented films. Significant improvement in crock fastness could not achieved with the addition of bentonite.

UV curable hyperbranched polyester polyurethane acrylate for hydraulic machinery coating

The content of river cement and sand in our country is relatively high, and the surface of hydraulic machinery in hydropower stations is often subject to fatigue damage and erosion. This topic is mainly used to solve the problem of abrasion and corrosion of hydraulic machinery coatings. UV curable polyurethane acrylate (PUA) can be quickly solidified into film and directly coated on the surface of hydraulic machinery with excellent anti-wear, adhesion properties and low cost. In this work, a hyperbranched polyester synthesized by the stepwise reaction of trimethylolpropane (TMP) and dimethylolpropionic acid (DMPA) was as a ‘nucleus’, and the polyurethane prepolymer was obtained by grafting IPDI and PTMG (C Schüll, H Frey, 2013 Grafting of hyperbranched polymers: from unusual complex polymer topologies to multivalent surface functionalization, Polymer, 54, 5443–5455). The UV-curing hyperbranched polyester polyurethane acrylate (PUA-1) was prepared by capping with HEA (Xu, W, Wang, W, Hao, L, Zhao, W, Liu, H, Wang, X 2020 Effect of generation number on properties of fluoroalkyl‐terminated hyperbranched polyurethane latexs and its films. J. Appl. Polym. Sci., e49215). Another UV-curing hyperbranched polyester polyurethane acrylate (PUA-2) was prepared as comparison by using TDI and PTMG as the main raw materials. Fourier Transform Infrared Spectrometer,1H-nuclear magnetic resonance spectroscopy, Gel Permeation Chromatography, thermogravimetric analysis and dynamic thermomechanical analysis were used to characterize its structure and properties. The wear rate of the two hyperbranched polyesters measured by the underwater steel ball method is below 3%, The swelling rate of PUA-1 is between 250%–300%, and the swelling rate of PUA-2 is around 260%, indicating that PUA-2 has better solvent resistance than PUA-1, and the internal structure of the film is more dense. TG analysis showed that the thermal stability of the two materials was good.

UV-LED as a New Emerging Tool for Curable Polyurethane Acrylate Hydrophobic Coating.

The elimination of mercury, low energy consumption, and low heat make the ultraviolet light-emitting diode (UV-LED) system emerge as a promising alternative to conventional UV-mercury radiation coating. Hence, a series of hydrophobic coatings based on urethane acrylate oligomer and fluorinated monomer via UV-LED photopolymerisation was designed in this paper. The presence of fluorine component at 1160 cm−1, 1235 cm−1, and 1296 cm−1 was confirmed by Fourier Transform Infra-Red spectroscopy. A considerably high degree C=C conversion (96–98%) and gel fraction (95–93%) verified the application of UV-LED as a new technique in radiation coating. It is well-accepted that fluorinated monomer can change the surface wettability as the water contact angle of the coating evolved from 88.4° to 121.2°, which, in turn, reduced its surface free energy by 70.5%. Hence, the hydrophobicity of the coating was governed by the migration of the fluorine component to the coating surface as validated by scanning electron and atomic force microscopies. However, above 4 phr of fluorinated monomer, the transparency of the cured coating examined by UV-visible spectroscopy experienced approximately a 16% reduction. In summary, the utilisation of UV-LED was a great initiative to develop green aspect in photopolymerisation, particularly in coating technology.

Synthesis and characterization of UV curable polyurethane acrylate derived from α-Ketoglutaric acid and isosorbide

A thermally stable coating of UV curable polyurethane acrylate (PUA) was prepared from bio-based PU and methyl 3-(4-hydroxy-3-methoxyphenyl)acrylate(MHPA). The presence of the aromatic ring in the backbone associated with MHPA imparts thermal stability in the structure. The bio-based PU was prepared through the condensation polymerization of hexamethylene diisocyanate(HDI) and a polyol prepared by the condensation reaction of α-ketoglutaric acid(KA) with isosorbide(IS). Isosorbide and α-ketoglutaric acid represent the replacement of the petroleum-based precursors used in polyol synthesis. Characterization of the new compound has been carried out using Fourier transform infrared spectroscopy(FT-IR) and nuclear magnetic resonance spectroscopy(NMR) and correlated with the quantitative analysis through hydroxyl and acid value. The UV curable PUA was added into the commercial polyurethane acrylate(CPUA) coating system and assessed based on their functional properties. The flexibility of the cured coating was determined by understanding the glass transition temperature through differential scanning calorimetry(DSC). Thermal gravimetric analysis was used to measure the thermal stability of the PUA and CPUA mixture. With an increase in the concentration of PUA, the thermal stability of the mixture improves. The structure of the prepared coating has been assessed using X-ray diffraction methods. The dynamic mechanical properties such as storage and loss modulus of the coating were determined from the rheological behavior. The mechanical properties and chemical/solvent resistance of the mixture were calculated and correlated with the gel content and moisture content. The nature of the fracture of the coating was observed through scanning electron microscopy(SEM).

Research on the Performance of Series Waterborne Polyurethane Acrylate Modified Epoxy Acrylates

In this study, a series of bifunctional-based UV curable waterborne polyurethane acrylate modified epoxy acrylate (UV-WPUA) was prepared by using 2,4-toluene diisocyanate (TDI), Epoxy resin (E51) and polyethylene glycol (PEG) as the main materials. Waterborne resin and UV curing film with content of C-O-C were obtained by using polyethylene glycols with different molecular weights. The infrared spectra (FT-IR) demonstrated the presence of C=C and epoxy bond in the UV curing film chains. In addition, the molecular weight of the oligomer, and glass transition temperature, gelation rate and thermogravimetric analysis of the films were investigated.

Synthesis of ultraviolet (UV)-curable water-borne polyurethane acrylate binders and comparison of their performance for pigment printing on synthetic leather

PurposeIn this study, it is aimed to synthesize ultraviolet (UV)-curable water-borne polyurethane acrylate (WPUA) binders using different types of polyols (poly (propylene glycol), PPG1000 and PPG2000 and poly (ethylene glycol), PEG1000 and PEG2000) at different molecular weights, DMPA (2,2-bis(hydroxymethyl) propionic acid) at different amounts and isophorone diisocyanate (IPDI) and use for pigment printing on synthetic leather.Design/methodology/approachUV-cured films were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimeter (DSC). The effect of binder structure on printing performance was determined with hardness, crock fastness, abrasion resistance and color measurements.FindingsThe highest abrasion resistance (60,000 cycles) and crock fastness values (dry crock and wet crock: 3/4) were obtained with binder PEG-C synthesized with PEG2000 and lower DMPA amount of 4.89 wt%; however, PEG-C binder showed lower hardness values. Due to lower urethane groups in PEG-C binder, more flexible films were obtained which imparted good adhesion property to printing film. Synthesized binders provided lower crock fastness and abrasion resistance properties than commercial WPUA binder.Originality/valuePigmented formulations including UV-curable water-borne synthesized PUA binder were developed and for the first time applied onto synthetic leather using screen printing method. Within this context, a new environmentally friendly printing method was proposed in this study including binder synthesis in the preparation of printing formulations.

Enhancing the Flame Retardancy of UV Curable Polyurethane Acrylate Coated Films with Alumina Trihydrate Filling

In this study, the flame retardancy of ultra violet (UV) curable polyurethane acrylate (PU) coated films were enhanced. For this aim, alumina trihydrate (ATH) filling material was mixed with the pastes including a photoinitiator and a UV curable PU. ATH filling ratio was preciously adjusted to obtain a uniform coating. The coated films were cured with a UV curing system equipped with gallium (Ga) and mercury (Hg) lamps. The chemical changes and the curing degree of the UV cured films were examined by a Fourier Transform Infrared Spectrum (FTIR) and a pendulum hardness tester. The thermal properties of the UV cured films were evaluated using a Differential Scanning Calorimeter (DSC). Moreover, vertical flammability and limiting oxygen index (LOI) measurements were conducted in order to determine the burning behavior of the UV cured films. The successful curing of the films was evidenced by means of FTIR results. The addition of ATH slightly increased the hardness values of the films. DSC results showed that ATH addition not only increased the enthalpy values but also enhanced the flame retardant property of the coated films and maximum LOI was achieved as 31.5%.  

Bio-based UV curable polyurethane acrylate: Morphology and shape memory behaviors

Smart bio-based shape memory polymers with high performance and fast response have the exciting potential to meet the growing need in biomedical applications.In this study, novel fast response UV-curable shape memory polyurethane acrylates (SMPUAs) comprising polycaprolactone diols (PCL-Diol), hexamethylene diisocyanate (HDI) and hydroxy-methyl methacrylate (HEMA) were synthesized by two-step bulk polymerization. Two series of PUAs with almost the same amount of hard segment content (HSC) were prepared with varying soft-segment molecular weight (2000, 3000, and 4000 g/mol) and different molar ratios of constituents. A mono-functional reactive diluent was used to control HSC and reduce the viscosity. Morphological characterization revealed nanoscale phase separation in SMPUAs. An increase in soft segment molecular weight was accompanied by an increase in the degree of microphase separation, crystallinity, and stiffness. The results indicated that shape memory behavior of PUAs was affected substantially by soft segment crystallinity and formation of stable ordered hard domains. The versatility of our SMPUAs was further reflected in good shape memory performance (higher than 97% fixity and recovery) with fast response as well as tunable transition temperature.

Screen printing of uv curable polyurethane acrylate binder prepared with different pigment concentrations on synthetic leather and gloss and hardness properties of printed films

In this paper, UV curing technology and screen printing method were firstly together applied on synthetic leather, in order to determine the gloss and hardness values of screen printed UV curable polyurethane acrylate binder films prepared with different pigment concentrations. UV curable water-borne pigmented formulations were prepared with different pigment concentration (3%, 5% and 7%) and two types of photoinitiators (Omnirad® 500 and Omnirad® 819 DW). The curing process were conducted under different combinations of lamps (Ga, Hg, GaHg and GaGaHg) at three power levels. Pendulum hardness and gloss values of printed films were investigated. In gloss measurements, higher gloss values were obtained at the pigment concentration of 3% at all lamp combinations. Moreover, the highest gloss value (20.96) of the sample printed with 3% pigment concentration was obtained at GaHg lamp combination at 679 mJ/cm2 energy density. The higher hardness values were obtained at a pigment concentration of 3% at all lamp combinations. The highest hardness value (9.8) of the pigmented polymeric films with 3% pigment concentration was obtained at GaGaHg lamp combination at 966 and 1663 mJ/cm2 energy densities. The results show that high gloss and hardness values can be achieved at lower pigment concentration of 3%. Considering energy efficiency, curing under the GaHg lamp combination at an energy intensity of 679 mJ/cm2 can be recommended for synthetic leather samples, which are printed with low pigment concentration (3%).

Inkjet-Printed CdTe Quantum Dots-Polyurethane Acrylate Thin Films

We demonstrated the inkjet-printed CdTe quantum dots-polyurethane acrylate thin films and their potential application in the display devices. The water soluble CdTe QDs were synthesized through the wet chemistry and the emission wavelengths can be freely tuned during the preparation process. Combining with the UV curable resin polyurethane acrylate, the QDs inks were prepared and the influence of diluent and water content on the performance of resultant films was studied. The tensile stress of the films cured from the QDs inks with diluent increased from 10.6 MPa to 27.5 MPa and the low water content led to uniform polymer matrix. Furthermore, the existence of diluent and low water content would all improve the fluorescence stability of the thin films. Finally, the thin films can be deposited on different substrates and well controlled to meet the RGB color standard, which will pave the way to a simple, low-cost, large-scale, and highly reliable method for the application of flexible displays.

Fabrication of Patchable Organic Lasing Sheets via Soft Lithography

Here, we report a novel fabrication technique for patchable organic lasing sheet based on non-volatile liquid organic semiconductors and freestanding polymeric film with high flexibility and patchability. For this work, we have fabricated the second-order DFB grating structure, which leads to surface emission, embedded in the freestanding polymeric film. Using an ultra-violet (UV) curable polyurethaneacrylate (PUA) mixture, the periodic DFB grating structure can be easily prepared on the freestanding polymeric film via a simple UV curing process. Due to unsaturated acrylate remained in the PUA mixture after UV curing, the freestanding PUA film provides adhesive properties, which enable mounting of the patchable organic lasing sheet onto non-flat surfaces with conformal contact. To achieve laser actions in the freestanding resonator structure, a composite material of liquid 9-(2-ethylhexyl)carbazole (EHCz) and organic laser dyes was used as the laser medium. Since the degraded active materials can be easily refreshed by a simple injection of the liquid composite, such a non-volatile liquid organic semiconducting medium has degradation-free and recyclable characteristics in addition to other strong advantages including tunable optoelectronic responses, solvent-free processing, and ultimate mechanical flexibility and uniformity. Lasing properties of the patchable organic lasing sheet were also investigated after mounting onto non-flat surfaces, showing a mechanical tunability of laser emission under variable surface curvature. It is anticipated that these results will be applied to the development of various patchable optoelectronic applications for light-emitting displays, sensors and data communications.

Process, Design and Materials for Unidirectionally Tilted Polymeric Micro/Nanohairs and Their Adhesion Characteristics.

Recent research in the field of gecko-inspired dry adhesive has focused on modifying the material and structural properties of polymer-based nanohairs. Polymers such as polystyrene (PS), high-density polyethylene (HDPE), ultraviolet curable epoxy (SU-8), polyurethane acrylate (PUA), polycarbonate (PC), and polydimethyl siloxane (PDMS) can fulfill many mechanical property requirements, are easily tunable, and can be produced via large-scale fabrication. However, the fabrication process for tilted structure remains challenging. The tilted structure is a crucial factor in high-degree conformal contact, which facilitates high adhesion, low effective modulus, and directional adhesion properties. Recent studies have attempted to create a tilted structure by applying beam irradiation, mechanical and thermal stress, and magnetic fields. This review provides a comprehensive investigation into advanced strategies for producing tilted polymeric nanostructures and their potential applications in the near future.