UV-cured Films Research Articles

Synthesis of Photosensitive Polyimides Incorporating Polydimethylsiloxane Segments and Studies on the Properties of their UV-Cured Films

Synthesis of Photosensitive Polyimides Incorporating Polydimethylsiloxane Segments and Studies on the Properties of their UV-Cured Films

Optimization of UV-Curable Polyurethane Acrylate Coatings with Hexagonal Boron Nitride (hBN) for Improved Mechanical and Adhesive Properties.

Polymer coatings are widely used in industries for protection, decoration, and specific applications, typically including volatile organic compounds (VOCs) to achieve low viscosity. The growing environmental concerns and the anticipated limits on fossil feedstock have driven the coating industry towards eco-friendly alternatives, with UV-curing technology emerging as a promising solution due to its energy efficiency, low-temperature operation, reduced VOC emissions, and high curing speed. Polyurethane acrylates (PUAs) are critical in UV-curable formulations, offering excellent flexibility, impact strength, optical, and adhesion properties. However, UV-cured PUA coatings face limitations in thermal stability and tensile strength, which can be addressed by incorporating fillers. This study investigates the effects of multi-functionalized hexagonal boron nitride (hBN) nanoparticles on the mechanical, thermal, optical, and adhesion properties of UV-cured PUA films and coatings for pre-coated metals. The results demonstrated that incorporating hBN nanoparticles enhanced the mechanical and thermal properties of the nanocomposite films, with optimal performance observed at 0.5% hBN loading. Despite the improved properties, the FTIR spectra indicated that the low concentration of hBN did not produce significant changes, potentially due to the overshadowing signals from the difunctional polyurethane acrylate.

A high-strength collagen-based antimicrobial film grafted with ε-polylysine fabrication by riboflavin-mediated ultraviolet irradiation for pork preservation

In this study, a UV-cured collagen-based film (C-P-H film) with high mechanical strength and antimicrobial properties was developed by riboflavin-mediated ultraviolet irradiation of collagen solution containing histidine-modified ε-polylysine. Fourier transform infrared analysis indicated that covalent cross-linking was formed between the collagen molecule and the histidine-grafted ε-polylysine. Compared with the pure collagen film, the C-P-H film containing 5 wt% histidine-modified ε-polylysine showed higher tensile strength (145.98 MPa), higher thermal denaturation temperature (76.5 °C), lower water vapor permeability (5.54 × 10−11 g m−1 s−1 Pa) and excellent antimicrobial activities against Escherichia coli and Staphylococcus aureus. In addition, the wrapping of the C-P-H film effectively inhibited bacterial growth of pork during storage time, successfully prolonging the shelf-life of pork by approximately 4 days compared to that of plastic wrap. These results suggested that collagen-based film grafted with histidine-modified ε-polylysine via riboflavin-mediated ultraviolet irradiation process had a great potential for pork preservation.

A robust, durable and eco-friendly UV-cured wood film with self-matting and anti-fingerprint performance via wrinkled structure

With the changes in people's living standards and aesthetic perspectives, the matting films with wrinkled surfaces play a crucial role in fields such as decorative materials, wooden furniture, wood-based panels and industrial coatings. In this paper, the UV-cured polyurethane acrylate (PUA) films with self-matting and anti-fingerprint performance on the wood-based panels was prepared and developed the wrinkled surface by using excimer/mercury dual UV curing. The results showed that the roughness, wavelengths (λ) and amplitudes (A) of wrinkles surface were positively correlated with the excimer irradiation time and negatively correlated with the mercury lamp irradiation time. Furthermore, the increasing irradiation time improved the degree of curing and crosslink density of the cured films, which enhanced the mechanical properties and durability of the cured film. Consequently, the prepared UV-cured PUA film exhibited excellent self-matting with a gloss of 3.4 GU at an incident angle of 60° and maintained the gloss value < 5 GU after 500 times rubs and 1 hour corrosion. Additionally, the self-matting films with wrinkled surface enhanced the hydrophobicity and anti-fingerprint performance of the surface. Besides, the cured film presented high physical performance with hardness of 4 H and adhesion of 0 grade. These results provide a reference for the further application of self-matting films in wood-based panels, furniture and interior decoration fields.

Advancing corrosion protection in confined spaces: a solvent-free UV LED-curable coating for steel pipelines with enhanced barrier properties and harsh environment performance

This study investigates a novel solvent-free, UV LED-curable coating as a robust corrosion protection solution for the inner surface of steel pipelines. The properties of the UV-cured film were characterized in terms of reactivity, thermomechanical properties, and adhesion to metal substrates. The coating was applied to the inside steel pipelines and cured using a patented UV LED lamp designed to fit in confined spaces. Finally, electrochemical impedance spectroscopy characterization and an accelerated cyclic electrochemical technique were performed on the coated pipes to study the corrosion protection properties of the coating, both with and without the addition of inorganic fillers. The results were compared to a commercially available thermally cured coating. It was found that the UV-cured coating confers high barrier properties, effectively preventing liquid penetration even under elevated temperature conditions. Furthermore, the corrosion protection performance in harsh environments was comparable to and, in some cases, higher than standard epoxy linings.

Construction of fluorinated hyperbranched polyaryletherketone-based UV-cured films with low dielectric and enhanced mechanical properties

The incorporation of hyperbranched structure into the polyaryletherketone (PAEK) is a crucial method for achieving a low dielectric constant (Dk), and the inclusion of crosslinked structure effectively reduces the dielectric loss (Df). This approach is of great significance in the development of high-quality communication at high frequencies. However, it is still a significant challenge for maintaining its mechanical properties and reducing Dk and Df due to the poor film-forming properties and low ductility of hyperbranched polymers. In this study, we synthesized a novel acrylate-based fluorinated hyperbranched photosensitive polyaryletherketone (hb-P6FAEK-Ace) as a prepolymer with various bifunctional aliphatic active and 4-acryloyl morpholine as the reactive solvent. Upon UV irradiation, cured films were obtained. This method significantly improved the mechanical properties of the hyperbranched UV-cured resin, with the tensile strength of CF-DCDDA of 83.2 MPa and the elongation at break of 7.61%. Additionally, the five prepared photosensitive resins exhibited excellent rheological properties (from 71.6 mPa s to 134.7 mPa s at 100 °C), rapid curing rates (within tens of seconds), and minimal volume shrinkage (<7%). Meanwhile, the Dk of CF-DCDDA was measured to be 2.87, with a Df of 0.0126 at the frequency of 20 GHz. This low dielectric expression for the crosslinked cured films could be ascribed to the confinement of electronic polarization caused by the crosslinked and hyperbranched structures. This work provides a simple, green, and promising strategy for enhancing the dielectric and mechanical properties of hb-PAEK.

Tough hyperbranched polyaryletherketone-based photosensitive resins bearing excellent dielectric property and thermal resistence

Organic polymer materials with low dielectric properties have garnered significant attention due to their convenient preparation process, low cost, and commendable mechanical properties. Such polymers, especially with heteromorphic structures, exhibited great potential for future electronic devices and antennas, particularly accompanied with rapid manufacturing technologies like three-dimensional (3D) printing. In this study, a series of new allyl ether-ended hyperbranched fluorene-based polyaryletherketone (hb-PFAEK-Allyls) were developed. The content of allyl ether photosensitive groups and molecular weight were controlled by adjusting the molar ratio of OH:F loading. UV-curable resins were then prepared through blending between hb-PFAEK-Allyls with trimethylolpropane triacrylate (TMPTA) and ethylene glycol bis(3-mercaptopropionate) (EGBMP), resulting in thiol-allyl-acrylate ternary UV-cured system. The influence of molecular weight of the hyperbranched polymers on the thermal performance, mechanical properties, and dielectric properties of the UV-cured films was systematically investigated. The results show that due to the introduction of hyperbranched structure with high molecular weight, the Tg of the UV-cured film can reach up to 248 °C. Due to the increased molecular free volume in the hyperbranched structure, the dielectric constant of the UV-cured film can be reduced to as low as 2.74 at 1 GHz. Due to the design of thiol-allyl-acrylate ternary UV-cured system, the cured film has excellent mechanical properties, with the highest tensile strength of 61.0 MPa and the elongation at break of 7.0%. This study represents innovative progress on integrating fully aromatic-based photosensitive hyperbranched polyaryletherketone into UV-curable resin architecture. Overall, the herein hb-PFAEK-Allyls-based photosensitive resins exhibit outstanding comprehensive performance and holds great potential for application in advanced 3D printing technology.

The Preparation of Acryloxyl Group Functionalized Siloxane Polymers and the Study of Their Ultra Violet Curing Properties.

Polysiloxane with multiple acryloxyl groups at the terminal site of the polymer chain was synthesized by the condensation reaction between hydroxyl-terminated polysiloxane and acryloyl chloride and used to improve the cross-linking density of UV-curable silicone materials initiated from dual acryloxy-terminated symmetric polysiloxane or single acryloxy-terminated asymmetric polysiloxane with the mixture of Irgacure 1173 and Irgacure 184 at a mass ratio of 1:1 as the photoinitiator. The effects of factors such as initiator composition, UV irradiation time, structure, and molecular weight of linear dual acryloxy-terminated or single acryloxy-terminated asymmetric siloxane oligomers on the gelation yield, thermal properties, water absorption, and water contact angle of UV-cured film were investigated. The synthesized cross-linking density modifier can be copolymerized with acryloxy-functionalized linear polysiloxanes under the action of a photoinitiator to increase the cross-link density of UV-cured products effectively. Both linear dual acryloxy-terminated or single acryloxy-terminated asymmetric siloxane oligomers can be copolymerized with cross-link density modifiers within 20 s of UV irradiation. The gelation yields of the UV-cured products obtained from the dual acryloxy-terminated siloxane oligomers were greater than 85%, and their surface water contact angles increased from 72.8° to 95.9° as the molecular weight of the oligomers increased. The gelation yields of UV-cured products obtained from single acryloxy-terminated asymmetric siloxane oligomers were less than 80%, and their thermal stabilities were inferior to those obtained from the dual acryloxy-terminated siloxane oligomers. However, the water contact angles of UV-cured products obtained from these single acryloxy-terminated asymmetric siloxane oligomers were all greater than 90°.

A novel method to synthesize polyurethane-urea acrylate with high strength and toughness

Photocurable oligomer with comprehensive mechanical performance has received increasing attention. However, it is an ongoing challenge to prepare strong and tough photocurable oligomer due to the well-known trade-off between strength and toughness. In this work, a novel strategy has been developed to synthesize polyurethane-urea acrylate (PUUA) with high strength and toughness. In our strategy, a new diol containing urea group was firstly synthesized, which was then used as chain extender to prepare PUUA. The employment of diol containing urea group to prepare PUUA can avoid the direct reaction between diamine and diisocyanate in the traditional synthetic strategy of PUUA. By changing the molecular structure of the chain extender, PUUA with different side chain was synthesized. The successful synthesis of PUUA was confirmed by FTIR and 1H NMR. The UV-cured PUUA film exhibited both high mechanical strength (31 MPa) and high toughness (39.5 MJ m−3), which was 1.24 and 1.45-fold increase compared with polyurethane acrylate (PUA) film without urea group. The simultaneously enhanced mechanical strength and toughness of PUUA film should be attributed to the formation of microphase separation, which has been proved by small-angle X-ray scattering (SAXS) test. This research represents an important and universal strategy to prepare PUUA with high mechanical strength and toughness.

Preparation of UV-cured polyurethane-urea acrylate coatings with high hardness and toughness

Polyurethane-urea acrylate (PUUA) has been used to develop mechanically robust materials, due to the urea-based bifurcated H-bond. However, the uncontrollable reaction rate between diamine and diisocyanate makes it difficult to prepare PUUA. Herein, we put forward a simple method to synthesize PUUA, which was then used to prepare UV-cured PUUA coatings with simultaneous high hardness and excellent toughness. In our strategy, a novel diol containing urea group has been designed, which was employed as chain extender to synthesize PUUA at a controllable polymerization rate. By adopting chain extenders with different molecular structures, two kinds of PUUA were synthesized. The molecular structures of diol containing urea group and PUUA were identified by Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance spectroscopy (1H NMR). Benefiting from the strong urea-based H-bond, the UV-cured PUUA films showed simultaneously enhanced mechanical strength and toughness. Specially, the optimal PUUA film exhibited high mechanical strength (19 MPa), high elongation at break (310 %), and high toughness (26.9 MJ m−3), which was 9.5, 2.8 and 19.2-fold increase compared with polyurethane acrylate (PUA) film without urea groups. Correspondingly, the UV-cured PUUA coatings exhibited higher impact resistance and higher hardness than PUA coating. This work provides a new avenue to develop PUUA for high-performance UV-curable coatings.

UV-curable polyimide/layered silicate films with improved barrier properties for the protection of semiconductor chips

Polyimide/layered silicate films can be used to protect semiconductor chips against gas and moisture permeation to prevent corrosion followed by failure of the electronic chip. The layered silicates in these films are used as barrier pigment to extend the diffusion pathway and to improve the barrier properties. However, the exfoliation of the silicates has an essential impact on the quality of the barrier. Films prepared from polyimide matrix with layered silicates were investigated as well as the distribution and orientation of silicate particles in the UV-cured film and the correlative mechanisms while hardening. The films were characterized by a variety of methods including SEM, FTIR, TGA, water vapor diffusion (WVD) and oxygen permeation measurement. The prepared films using polyimide / layered silicates nanocomposites showed a reduction of WVD and oxygen permeation of 30% and 80%, respectively. Results demonstrated that polyimide/layered silicate nanocomposite could be used as barrier coating to reduce the permeation of moisture and gases.

Influence of Mechanical Properties on the Piezoelectric Response of UV-Cured Composite Films Containing Different ZnO Morphologies

ZnO flower-like (ZFL) and needle (ZLN) structures were synthesized and embedded into UV-curable acrylic resin (EB), with the aim to study the effect of filler loading on the piezoelectric properties of the resulting composite films. The composites showed uniform dispersion of fillers within the polymer matrix. However, by increasing the filler amount, the number of aggregates increased, and ZnO fillers appeared not to be perfectly embedded in polymer film, indicating poor interaction with acrylic resin. The filler content increase caused an increase in glass transition temperature (Tg) and a decrease in storage modulus in the glassy state. In particular, compared with pure UV-cured EB (Tg = 50 °C), 10 wt.% ZFL and ZLN presented Tg values of 68 and 77 °C, respectively. The piezoelectric response generated by the polymer composites was good when measured at 19 Hz as a function of the acceleration; the RMS output voltages achieved at 5 g were 4.94 and 1.85 mV for the composite films containing ZFL and ZLN, respectively, at their maximum loading levels (i.e., 20 wt.%). Further, the RMS output voltage increase was not proportional to the filler loading; this finding was attributable to the decrease in the storage modulus of the composites at high ZnO loading rather than the dispersion of filler or the number of particles on the surface.

Selecting adhesive molecular layers with matched surface free energy and chemisorption for shape-fixed UV-cured thin films fabricated by laser-drilled screen printing and UV nanoimprinting

This study investigates the importance of surface free energy and chemisorption of substrates for the formation of a UV-cured thin film corresponding to a residual layer in UV nanoimprint lithography. Silicon substrate surfaces were modified with binary molecular layers which were prepared through photo-oxidation of a monomer-repelling monolayer and implantation of a reactive surface modifier with an acrylate polymerizable group. Laser-drilled screen printing enabled the placement of droplets of high-viscosity dimethacrylate UV-curable liquid on the modified substrates. UV nanoimprinting with a modified flat mold surface allowed the formation of UV-cured films with a square shape and a sub-100 nm thickness. The thickness of the UV-cured film was tuned precisely in the case of the substrate showing almost the same surface free energy value as the mold surface. The comparison with and without the reactive surface modifier revealed that the chemisorption was essential for the film formation on the substrates.

Synthesis and characteristics of cardanol-based acrylates as reactive diluents in UV-curing coatings

Two types of cardanol epoxy acrylates (CAR1 and CAR2) were synthesized from bio-based cardanol and used as a reactive diluent. Their dilution effect, curing properties, and thermal and physical properties of UV-cured films as a reactive diluent were compared to those of commercial reactive diluent, 2-phenoxyethyl acrylate (PHEA). CAR series showed a lower dilution effect due to their relatively high viscosity compared to PHEA. However, 10 wt% CAR-diluted films showed similar reactivity and high thermal stability compared to 10 wt% PHEA diluted film, indicating CAR series can be used as partial alternatives to PHEA.

Synthesis of a Dipyridyl Disulfide Cross-linking Reagent and Its Application to Photo-adhesion of Dissimilar Materials

Photo-adhesion of dissimilar materials was performed by using a diacrylate cross-linking reagent containing a 2,2'-dipyridyl disulfide moiety. Cross-linking reagent designed in this work was purified by recrystallization. UV-cured films were fabricated with the cross-linking reagent, 4-hydroxybutyl acrylate and a radical photo-initiator. Hydrophilicity of the film surface seemed to be changed larger than that of control samples. In photo-adhesion experiments, 0.3-2.5 MPa of shear stress was recorded after 1 J/cm2 of UV irradiation at a wavelength of 365 nm. Remarkable improvement of adhesive strength was observed when copper adherends were used, suggesting interaction between copper surface and sulfur atoms of the dipyridyl disulfide moieties in the adhesive layer.

Design, synthesis and properties of trifluoromethyl polysiloxane oxetane monomers

The oxetane is widely used in cationic photopolymerization, while fluorosilicone polymers combine the advantages of organosilicone and organofluorine. In this study, a series of trifluoromethyl polysiloxane oxetane monomers with different chain length (XE-FSin, n = 3, 6, 9) was designed and synthesized by a simple two-step synthesis procedure, and low-cost and easily available raw materials. XE-FSin exhibited good photopolymerization property and ability to boost the photopolymerization of the alicyclic epoxy monomers, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate (E4221) and 1,2-epoxy-4-vinylcyclohexane (VOH). The final conversions of the alicyclic epoxy group and the oxetane group of the systems with XE-FSi3 after 900 s of the irradiation reached up to 80.8 % and 75.2 %, respectively. The introduction of XE-FSin improved the thermal stability, glass transition temperature (Tg) and tensile property of the UV-cured film because of the presence of trifluoromethyl group and polysiloxane chain. The surface of the UV-cured film of XE-FSi9-0.5 % system had the highest water contact angle that was 108.4°. The tensile strength and elongation at break of the UV-cured film of XE-FSi3-0.5 % system were 0.85 MPa and 67.87 %, respectively, and three times more than those of XE-FSi3-0 % as the blank control. With the increase of the chain length of XE-FSin, the Tg, adhesion force and pencil hardness of the UV-cured film had no significant changes.

Preparation and relationship between structure and properties of PTMEG based polyurethane acrylate UV cured films

A series of polyurethane acrylate UV curing films (FPUA) were designed and prepared from three different hard segment structure, hard segment content and NCO/OH molar ratio via prepolymer process from polytetramethylene ether glycol(PTMEG), diisocyanate and polycaprolactone modified acrylate (FM1D). And the influence of structural parameters on the cured films’ mechanical properties was studied; Besides, its thermal properties was characterized by Dynamic Thermomechanical Analysis (DMA) and Thermo Gravimetric Analyzer (TGA). Among these three hard segment structures, hexamethylene diisocyanate (HMDI) -based cured films have the best mechanical properties. The modulus and tensile strength of the cured films increases along with the increase of hard segment content, whereas the elongation at break of the cured films decreases since the rising of the NCO/OH molar ratio. Indeed, with hard segment content at 48.6% and NCO/OH molar ratio at 1.06, the UV cured films (exhibits the best performance)with tensile strength up to 50.5 MPa, and break elongation upto238%. DMA and TGA data showed that the low-temperature glass transition temperature of UV-cured films is around −50 °C, and the fastest thermal degradation temperature is 355 °C, showing good resistance to high and low temperatures.

Nondestructive x-ray reflectivity analysis of Al distributions of ultraviolet-cured spin-coated resist films hybridized with trimethylaluminum

Ultraviolet (UV)-cured spin-coated resist films of 100 nm and thinner thicknesses made with bisphenol A-based dimethacrylate monomers on silicon substrates were hybridized by multiple-pulsed vapor infiltration of sequential trimethylaluminum (TMA) doses and a final H2O dose. Nondestructive x-ray reflectivity measurements without film shrinkage enabled characterization of the internal layer structures of the UV-cured films unmodified before hybridization and hybridized by TMA infiltration and chemical fixing. It was possible to determine the thickness, density, and interface roughness of each layer in the unmodified and hybridized UV-cured films. The TMA infiltration and chemical fixing resulted in the formation of the highest-density Al-rich layer near the film surface. The presence of the highest-density layer arising from the most abundant component, Al, was confirmed through energy-dispersive x-ray spectroscopy and time-of-flight secondary ion mass spectrometry. The increase in the cycle number of TMA dose from 100 to 150 and 200 cycles had little effect on organic–inorganic hybridization of the 100 nm-thick UV-cured films. The thickness of the outermost Al-rich layer near the film surface was approximately 30 nm, which was unchanged when the film thicknesses of 100, 75, and 50 nm were changed. The outermost skin layer suppressed the infiltration of TMA into the UV-cured films. The infiltration of TMA into the UV-cured films progressed as the film thicknesses decreased.

Physicochemically constructed zinc oxide and UV-curable polymer hybrid films for liquid crystal system

UV-nanoimprint lithography was performed with zinc oxide (ZnO) solution and a UV-curable polymer. The UV-curing time was 2, 4, or 6 min, after which the surfaces of the films were analyzed. Atomic force microscopy of the physical characteristics of the surfaces revealed that the clearest pattern was attained on the 6 min UV-cured film. Moreover, X-ray photoelectron spectroscopy analysis confirmed that varying the UV exposure time changed the composition of atoms and bonds on the surfaces of the films. Light transmittance measurements of the patterned ZnO hybrid films show that they all exhibited sufficient transmittance. To investigate the liquid crystal (LC) orientation, LC cells were fabricated with the various films into antiparallel structures. Polarized light microscopy confirmed stable LC alignment while a stable transmittance curve based on pretilt angle measurements was observed in LC cells fabricated with hybrid films exposed to UV light for more than 4 min. The relationship between the height of the groove pattern in the film and the alignment of the LC molecules was analyzed by using Berreman's model.

Preparation and UV curing properties of oxazolidinone-based acrylate derivatives

The oxazolidinone-based acrylate derivatives were prepared by the oxa-Michael addition reaction of neopentyl glycol diacrylate (NPGDA), trimethylolpropane triacrylate (TMPTA) and ethylene glycol dimethacrylate (EGDMA) with 3-(2-hydroxyethyl)-2-oxazolidinone (Z1), which was prepared by the reaction of dimethyl carbonate (DMC) with diethanolamine (DEA). The molecular structures of the products were characterized by FT-IR, 1H NMR and electrospray ionization high resolution mass spectrometry (ESI-HRMS). Under initiated by 1 wt% 2-isopropyl-9H-thioxanthen-9-one (ITX) and 1 wt% 2-hydroxy-2-methyl-1-phenylpropan-1-one (Da-1173), the oxazolidinone- based acrylates were cured in 30 s with double bond conversion of 92% and 98%, respectively. The photopolymerization activity is in the order of oxazolidinone-based acrylate > conventional acrylate with 3 wt% EDB > conventional acrylate. The first-order kinetics for oxazolidinone part indicates that the oxazolidinone group is a hydrogen donor, which can terminate the polymeric radicals, forming an active radical to re-initiate the polymerization. HRMS analysis of oligomers extracted from the UV-cured film of butyl acrylate confirms further the role of oxazolidinone part, and the plausible UV polymerization mechanism was proposed. The composition of addition product of TMPTA with Z1 (named as TMPTA-Z1) with epoxy acrylate can be 3D printed forming various models with the hardness of 5H.