Search Results (51)

Ultraviolet light-emitting diode (UV LED) technology offers advantages over conventional UV mercury (UV Hg) lamps, including precise wavelength control, high energy efficiency and rapid curing. While UV LED is widely applied in sectors like dentistry, printing, and electronics, its application in contact lens manufacturing remains relatively low. This study evaluates the feasibility of integrating UV LED technology curing as a replacement for UV Hg lamps to produce silicone hydrogel contact lenses. Many manufacturers utilizing UV Hg systems encounter challenges such as extended curing times and increased cosmetic defect rates. In this study, lenses were formulated using a mixture of hydrophobic macro-monomer, silicone monomer, and hydrophilic monomer. The formulations were cured using both UV LED and UV Hg lamps systems under controlled intensities, and two curing configurations were assessed: single-sided (SC) and double-sided (DC). The UV Hg light intensity was maintained between 1.1 and 3.1 mW/cm², reflecting standard production values, while the UV LED intensity was set at 32 mW/cm² to ensure uniform light distribution in the mold. The findings showed an improved degree of conversion (DOC) for UV LED cured lenses (86–88%) compared to UV Hg (79.5–82.3%), along with increased water content (ranging between 34 and 36.8%) and ion permeability (7.1–8.3 mm²/min). The optical properties of the cured lenses remained consistent across both methods. Notably, UV LED curing reduced cosmetic defects by up to 50% and shortened curing time by 3 to 4 times. These enhancements support UV LED as a superior alternative for contact lens curing, enabling scalable, efficient, and high-quality manufacturing. Full article

This study developed a waterborne UV-curable acrylic composite coating incorporated with carved lacquer powder and systematically investigated the effects of powder and deionized water content on its properties. The results showed that the carved lacquer powder content significantly influenced the optical, mechanical, and curing behaviors of the coating, while the water content had negligible impact. Specifically, increasing the powder content reduced lightness, enhanced red hue, and decreased gloss. An optimal comprehensive performance was achieved at 20% powder content, with adhesion reaching grade 5, flexibility of 10 mm, and impact resistance of 6 kg·cm. FTIR analysis confirmed that high powder content (≥20%) led to incomplete curing due to UV shielding. The coatings showed moderate resistance to water, acid, and saline environments but poor alkaline resistance due to the chemical instability of cinnabar. SEM revealed increased surface roughness at high powder loading (30%). More importantly, this work presents a sustainable approach to recycle carved lacquer waste and demonstrates a viable strategy for incorporating traditional cultural heritage materials into advanced functional coatings. The study demonstrates that carved lacquer powder can be effectively integrated into UV-curable coatings to achieve unique decorative effects, and a content of approximately 20% is recommended to achieve balanced properties. Full article

Wood flour, a landscaping byproduct, poses disposal challenges due to its poor degradability, despite its potential as a sustainable material. This study modified wood powder by synergistically incorporating fly ash and TiO₂, followed by curing it with polyamide and epoxy resin to produce high-performance wood powder-based composites suitable for outdoor furniture applications, it can solve the environmental problems caused by fly ash. The research findings indicated that as the TiO₂ content increased, the material’s pore size diminished, structural strength improved, and it demonstrated enhanced hydrophobic properties and UV absorption capabilities. The optimal UV absorption performance was observed at a TiO₂ content of 1.5%. The combination of TiO₂ and fly ash led to the formation of more stable Si-O-Ti and Si-O-Si bonds, which further strengthened the material. Water contact angle and water repellency tests indicated that the 1.5% TiO₂ composite showed a 12% increase in compressive strength and a water contact angle of 100.6°, indicating improved hydrophobicity. The addition of TiO₂ reduced the number of free-OH groups within the matrix, thereby improving the composite’s hydrophobicity. Outdoor chairs fabricated by mixing 1.5% TiO₂-modified wood powder with PET for demolding exhibited excellent structural stability while also being safe and environmentally friendly. This study proposes a feasible preparation strategy for wood powder, enhancing durability through improved mechanical strength, water repellency, and UV shielding. Furthermore, it offers valuable insights into the material modification of wood powder-based materials for the production of outdoor garden furniture. Full article

This study investigates the influence of photoinitiating systems on the degree of methacrylate group conversion and the rate of polymerization in UV/LED-curable nail gel formulations. Camphorquinone and Eosin Y, commonly used in medical and dental applications, were evaluated in bimolecular systems with onium and iodonium salts, thiols, and amines as co-initiators. Real-time FT-IR spectroscopy was employed to monitor polymerization under dual-LED irradiation (365 nm and 405 nm). The results demonstrate that the tested systems, inspired by photocurable medical products, exhibit significant potential for application in highly pigmented nail gels, achieving efficient curing with low residual monomer content. Full article

The exposure parameters in stereolithography with liquid crystal display (SLA-LCD) influence the functional properties of photopolymers, which is particularly important for tribological applications. In this study, the influence of the exposure time of the layers (2–8 s) on the surface topography (ISO 25178), Brinell hardness (HB) and chemical structure (FTIR spectroscopy) of UV-cured resin samples is investigated. Both insufficient and excessive UV irradiation led to undesirable effects ranging from incomplete cross-linking and surface irregularities to excessive curing, micro-cracking and increased surface kurtosis (high Sku values). The most balanced mechanical and topographical performance was observed at a layer exposure time of 6 s, characterised by low Spk values, uniform surface texture and high cohesion between layers. FTIR analysis confirmed the progressive cross-linking with increasing exposure time. The results show that precise control of irradiation parameters enables optimisation of the interrelationships between microstructure, mechanical properties and surface functionality, which is critical for improving the durability and performance of components operating under boundary or mixed lubrication. Full article

The aim of this in vitro study is to evaluate the effect of resin type and placement technique on the hardness of resin-based composites (RBCs). A total of 300 samples consisting of five RBCs (Filtek Z250 microhybrid, Filtek P60 packable, Tetric Ceram hybrid, Admira ORMOCER, and Tetric Flow flowable RBCs) were prepared. Each RBC was placed into Teflon molds with a 4 mm diameter and 2 or 8 mm depths with standard, bulk and incremental techniques and was polymerized by second-generation LED (Hilux Ledmax 1055, 229.153 mW/cm²) and UV (ELC-410, 26.106 mW/cm²) light-curing units (LCUs) in standard mode (n = 10). The Vickers hardness number (VHN) was measured from the top and bottom surfaces of the RBCs. Data were statistically analyzed with a one-way ANOVA. Multiple comparisons were made using the Tukey, Scheffe, and t-tests (p < 0.05). The VHN of the RBCs polymerized with LED and UV LCUs varied between 110.33 and 25.16 and between 104.86 and 34.20, respectively. The Tetric Flow RBC did not polymerize with the LCUs on either surface. The RBCs placed using the bulk technique could not polymerize with the UV LCU on the top surface, except for the Filtek P60 RBC, but showed a higher VHN on the bottom surface. These significant findings highlight that the hardness is specific to the RBC material and placement technique. Full article

A novel monomer, 9-bis[4-(2-hydroxyethoxy)phenyl]fluorene di(mercaptopropionate), with a highly refractive index, purity, and excellent UV-curable properties, is synthesized through an optimized Fischer esterification process, reacting 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene with 3-mercaptopropionic acid. The structural characterization of this monomer is performed using Fourier-transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, and liquid chromatography-mass spectrometry. The synthesis conditions are optimized using a design-of-experiments approach. UV-curable resins are obtained by incorporating the synthesized monomer as the thiol component. The effects of thiol content on the UV-curing behavior, refractive index, shrinkage, adhesion to the polyethylene terephthalate (PET) foil, and viscoelastic recovery are examined. The thermal properties are assessed using differential scanning calorimetry and thermogravimetric analysis. Field-emission scanning electron microscopy confirms the successful replication of the prism film. In edge-lit light-emitting diode (LED) backlight units, the prism film showed increased luminance with higher thiol monomer content in the UV-curable resin while maintaining stable color coordinates. This novel highly refractive index monomer can be utilized in luminance-enhancing prism films, thereby contributing to future innovations in the display film industry. Full article

This study analyzes the influence of energy generated by emitters on the adhesive properties of varnish coatings in multilayer UV systems. The experimental material, in the form of a cell board finished with UV varnish products, was prepared on a prototype line under the conditions of Borne Furniture in Gorzów Wielkopolski. The roughness and wettability were measured using a OneAttension tensiometer integrated with a topographic module, taking into account the Wenzel coefficient. The adhesion of the examined systems was verified using the PositiTest AT-A automatic pull-off device. Energy consumption by the prototype production line was compared to the standard line, utilizing mercury emitters and mercury emitters with added gallium. Energy consumption was calculated for selected variants. The influence of the Wenzel coefficient on the wettability angle was observed. Significant differences between contact angles (CA and CAc) were noted for coatings formed with sealers (stages I and II). The largest discrepancies, reaching up to 30 degrees, were recorded at the lowest UVA and UVV doses of 26 mJ/cm². In adhesion tests, values below 1 MPa were obtained. Insufficient energy doses in the curing process of UV systems led to delamination between the coatings. Five variants were selected where delamination within the substrate predominated (˃90% A) and were characterized by the lowest energy consumption in the processes. Topographic images helped identify the presence of various surface microstructures at different stages of the production cycle. The greatest energy savings, up to 50%, were achieved in stages III and IV of the technological process. Full article

This study aims to investigate the effects of three toughening agents—core–shell rubber particles (CSR), nano-silica particles (NSPs), and epoxidized polybutadiene (EPB)—on the performance of UV-LED-cured epoxy electronic encapsulants. By systematically comparing the curing behavior, thermomechanical properties, and impact resistance of different toughening agents in alicyclic epoxy resins, their potential applications in more environmentally friendly UV-cured electronic encapsulation are evaluated. The results show that NSP and CSR toughened samples have fast cured speed under 365 nm UV-LED light, but it affects the depth of curing under low energy conditions. They maintain high Tg, high modulus, and low thermal expansion coefficient (CTE), especially in the NSP-toughened sample. The EPB-toughened sample has good transparency for LED, but it has negative effects on Tg and CTE. This research provides essential theoretical and experimental data to support the development of high-performance UV-LED-cured epoxy encapsulation materials. Full article

This study investigates the crosslinking dynamics and swelling properties of pH-responsive poly(ethylene glycol) (PEG)/poly(acrylic acid) (PAA) interpenetrating polymer network (IPN) hydrogels. These hydrogels feature denser crosslinked networks compared to PEG single network (SN) hydrogels. Fabrication involved a two-step UV curing process: First, forming PEG-SN hydrogels using poly(ethylene glycol) diacrylate (PEGDA) through UV-induced free radical polymerization and crosslinking reactions, then immersing them in PAA solutions with two different molar ratios of acrylic acid (AA) monomer and poly(ethylene glycol) dimethacrylate (PEGDMA) crosslinker. A subsequent UV curing step created PAA networks within the pre-fabricated PEG hydrogels. The incorporation of AA with ionizable functional groups imparted pH sensitivity to the hydrogels, allowing the swelling ratio to respond to environmental pH changes. Rheological analysis showed that PEG/PAA IPN hydrogels had a higher storage modulus (G′) than PEG-SN hydrogels, with PEG/PAA-IPN5 exhibiting the highest modulus. Thermal analysis via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated increased thermal stability for PEG/PAA-IPN5 compared to PEG/PAA-IPN1, due to higher crosslinking density from increased PEGDMA content. Consistent with the storage modulus trend, PEG/PAA-IPN hydrogels demonstrated superior mechanical properties compared to PEG-SN hydrogels. The tighter network structure led to reduced water uptake and a higher gel modulus in swollen IPN hydrogels, attributed to the increased density of active network strands. Below the pK_a (4.3) of acrylic acid, hydrogen bonds between PEG and PAA chains caused the IPN hydrogels to contract. Above the pKa, ionization of PAA chains induced electrostatic repulsion and osmotic forces, increasing water absorption. Adjusting the crosslinking density of the PAA network enabled fine-tuning of the IPN hydrogels’ properties, allowing comprehensive comparison of single network and IPN characteristics. Full article

UV-activated catalytic hydrosilation is a low-temperature crosslinking process that has attracted attention for its high efficiency and lower energy demand relative to thermal curing. In this study, formulations comprising industrially relevant model silanes and Pt photocatalysts trimethyl(methylcyclopentadienyl)platinum(IV) and trimethyl(pentamethylcyclopentadienyl)platinum(IV) (MeCpPtMe₃ and Cp*PtMe₃, respectively) were prepared with and without a photosensitizer (PS) and assessed for catalytic performance by a novel strategy. Photopolymerizations were initiated using different wavelengths from LEDs and monitored in real-time using an Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) “well” strategy to track the degree of cure in ultra-thin films by consumption of hydride via the disappearance of the Si-H bending absorption band at 915 cm⁻¹. Irradiation of formulations with 365 nm excitation showed higher conversions relative to 400 nm light and improvements to calculated initial reaction rates by incorporation of a PS suggested increased sensitization to 365 nm irradiation. To the best of our knowledge, this is the first study to report catalytic performance, electronic absorption spectroscopic data, and the crystal structure of Cp*PtMe₃. Full article

In this study, polyacrylic acid hydrogels were prepared by modulating the cross-linking agent mass ratio using UV and heat curing methods. The structures and properties of the hydrogels were characterized and analyzed using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results showed that the mechanical properties of the hydrogels prepared through UV curing were better than those prepared through heat curing. The maximum mechanical tensile strength of 139 kPa was achieved at a cross-linking agent mass ratio of 3.85% with 20 min of UV curing, and the maximum mechanical compressive strength of 0.16 MPa was achieved at a cross-linking agent mass ratio of 2.91% with 20 min of UV curing. However, the hydrogels prepared by heat curing had a higher tensile strength than those prepared using the heat curing method. In addition, the thermally cured hydrogels had higher water absorption and adsorption properties. Moreover, the PAA hydrogels prepared at cross-linking agent mass ratios of 1.91 and 2.91% with 2 h of the heat curing method had the best swelling properties. Moreover, the increase in the cross-linker mass concentration led to a decrease in the pore size and porosity and to a more compact structure. Full article

This study describes the development of hydrogel formulations with ionic crosslinking capacity and photocatalytic characteristics. The objective of this research is to provide an effective, accessible, “green”, and facile route for the decontamination of chemical warfare agents (CWAs, namely the blistering agent—mustard gas/sulfur mustard (HD)) from contaminated surfaces, by decomposition and entrapment of CWAs and their degradation products inside the hydrogel films generated “on-site”. The decontamination of the notorious warfare agent HD was successfully achieved through a dual hydrolytic–photocatalytic degradation process. Subsequently, the post-decontamination residues were encapsulated within a hydrogel membrane film produced via an ionic crosslinking mechanism. Polyvinyl alcohol (PVA) and sodium alginate (ALG) are the primary constituents of the decontaminating formulations. These polymeric components were chosen for this application due to their cost-effectiveness, versatility, and their ability to form hydrogen bonds, facilitating hydrogel formation. In the presence of divalent metallic ions, ALG undergoes ionic crosslinking, resulting in rapid gelation. This facilitated prompt PVA-ALG film curing and allowed for immediate decontamination of targeted surfaces. Additionally, bentonite nanoclay, titanium nanoparticles, and a tetrasulfonated nickel phthalocyanine (NiPc) derivative were incorporated into the formulations to enhance absorption capacity, improve mechanical properties, and confer photocatalytic activity to the hydrogels obtained via Zn²⁺—mediated ionic crosslinking. The resulting hydrogels underwent characterization using a variety of analytical techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), viscometry, and mechanical analysis (shear, tensile, and compression tests), as well as swelling investigations, to establish the optimal formulations for CWA decontamination applications. The introduction of the fillers led to an increase in the maximum strain up to 0.14 MPa (maximum tensile resistance) and 0.39 MPa (maximum compressive stress). The UV-Vis characterization of the hydrogels allowed the determination of the band-gap value and absorption domain. A gas chromatography–mass spectrometry assay was employed to evaluate the decontamination efficacy for a chemical warfare agent (sulfur mustard—HD) and confirmed that the ionic crosslinked hydrogel films achieved decontamination efficiencies of up to 92.3%. Furthermore, the presence of the photocatalytic species can facilitate the degradation of up to 90% of the HD removed from the surface and entrapped inside the hydrogel matrix, which renders the post-decontamination residue significantly less dangerous. Full article

Ultraviolet (UV) curing is an efficient and environmentally friendly curing method. In this paper, UV-cured polyurethane acrylates (PUAs) were investigated as potential military coatings to serve as barriers against chemical warfare agents (CWAs). Seven UV-cured PUA coatings were formulated utilizing hydroxyethyl methacrylate-capped hexamethylene diisocyanate trimer (HEMA-Htri) and trimethylolpropane triacrylate-capped polycarbonate prepolymer (PETA-PCDL) as the PUA monomers. Isobornyl acrylate (IBOA) and triethyleneglycol divinyl ether (DVE-3) were employed as reactive diluents. Gas chromatography was utilized to investigate the constitutive relationships between the structures of the PUA coatings and their protective properties against simulant agents for CWAs, including dimethyl methylphosphonate (DMMP), a nerve agent simulant, and 2-chloroethyl ethyl sulfide (CEES), a mustard simulant. The glass transition temperature (T_g) and crosslinking density (υ_e) of PUAs were found to be crucial factors affecting their ability to serve as barriers against CWAs. The incorporation of IBOA units led to enhanced T_g and barrier performance of the PUAs, resulting in a DMMP retention of less than 0.5% and nearly 0 retention of CEES. However, an excessive introduction of polycarbonate chains decreased the υ_e and barrier performance of the PUAs. These findings may offer valuable insights for enhancing the protection of UV-cured PU coatings against CWAs. Full article

The coating process involves applying a thin material layer to a surface to engender it with specific desirable properties or enhance its performance. In the production of print media (labels, packaging, printed textiles, and promotional materials), the standard functions of the coating process include visual decoration, which involves the addition of appealing colors, textures, and patterns. A pertinent issue in the printing industry is that at present, the predominant coating process uses printing and coating technologies (gravure, flexo, letterset, letterpress, screen printing, inkjet, and electrophotography) and lamination (i.e., attaching decorative layers of materials, such as films or fabrics). In this paper, we present a new method for testing the efficiency with which different-sized metalized printing elements (using gold foil) may be applied to paper substrates; to do so, we gradually vary the amount UV-cured inkjet varnish (or adhesive) that is applied. To test the effectiveness of this method in producing metallic visual effects, we utilize seven different thicknesses of UV-cured varnish with the aid of modular piezo inkjet heads (KM1024 iLHE-30) and three different printing speeds. Our research shows that to achieve optimal production of cold metalized foil, a 21 µm layer should be deposited, and the substrate should move at a speed of 0.30 m/s. Full article