UV-curable Materials Research Articles

Study on UV-Curable Acrylic Clear Viscoelastic Materials with Grafted Structures

Flexible substrates are crucial for wearable electronic strain sensors, but achieving biocompatibility, low cost, and aesthetic appeal alongside good mechanical performance remains challenging. Acrylic-based clear viscoelastic films (CVFs) are gaining attention due to their excellent transparency and potential for enhanced mechanical properties. This study synthesized copolymers CVF1-4 with varying branch content using soft monomers 2-ethylhexyl acrylate (2-EHA), butyl acrylate (n-BA), and functional monomer acrylic acid (AA). Employing a "grafting-through" strategy, small molecule monomers, ATRP-synthesized oligomer pBA25, and photoinitiator 1,6-hexanediol diacrylate (HDDA) were in-situ polymerized under UV light to form transparent, flexible elastic films CVF1-4. Between -20 to 80 C, CVF1-4 demonstrated excellent mechanical properties such as low modulus (in the kPa range), low glass transition temperature (below -20 C), large deformation (500-600%), and high strain recovery rate (>95%). Among them, CVF3 with 15% branching showed a balanced comprehensive performance, exhibiting primarily elastic behavior at room temperature. Therefore, selecting appropriate molecular composition and grafting structure provides a simple and customizable solution for optimizing CVF properties.

Oxime esters: Potential alternatives to phosphine oxides, for overcoming oxygen inhibition in material jetting applications

Material jetting technology is emerging as a prominent technique within the additive manufacturing domain for printing multi-material objects. Despite its various advantages, including high printing resolution, oxygen inhibition remains the main issue for UV-curable materials. Oxime esters are interesting photoinitiators for this application due to their ability to undergo a photocleavage reaction followed by decarboxylation, limiting the diffusion of oxygen. A series of four commercially available oxime esters were studied as Type I photoinitiators, with the photoinitiating ability and photochemical properties of two of them never having been investigated before. Initially, their UV–visible absorption properties were studied, revealing significant absorption up to 420nm. Photopolymerization kinetic studies indicate that the oxime esters can outperformed benchmark photoinitiators such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) by reaching around 80% of double bond conversion in 12µm layer under air (for O-16) against 60% for BAPO under the same conditions. Finally, the oxime esters were tested in 3D-inkjet printing applications, displaying highly promising results with tack-free surfaces.

Photocurable vitrimers with malleable and self-healing trade-off enabled by manipulating dynamic boronic ester bonds

Although numerous strategies refer to dynamic covalent bond exchanges of small molecules for self-repairing thermosets, it remains a critical challenge to be able to jointly tune the malleability and dynamic properties of photocurable materials via extending dynamical small molecule bridging chains with tunable kinetic features. Herein, we successfully synthesized two typical diboronic ester molecules (diboronic ester dithiol/diacid) with variable dioxaborolane metathesis kinetics, which acted as dynamical interlinking segments constructing simple hydrogenated bisphenol A (HBA) epoxy backbone to achieve dynamically cross-linking feature. Subsequently, the acrylate- and anhydride-modified HBA vitrimers bearing diboronic ester-extending segment variants and photocuring traits are successfully synthesized by a one-pot reaction. Consequently, it is demonstrated that the embedded amounts of dynamic diboronic ester bonds in the backbone play a key role in the photopolymerization rate of photocurable vitrimers. The photopolymerization rate decreases significantly as more diboronic ester segments. Moreover, the diboronic ester dithiol-mediated photocurable vitrimer (HBA-S) exhibits enhanced malleability (strain at break of 26.6 %), desirable photo-crosslinked network, and accelerated thermal-triggered self-healing ability (scratch self-healing efficiency of closing to 100 % at 150 °C), compared to those of the diboronic ester diacid-mediated vitrimer (HBA-O) under identical conditions. This work validates the probability of transferring the dioxaborolane metathesis of small molecules to dynamic properties of bulk UV-curing materials, which provides valuable guidance for the rational design and fabrication of tunable dynamic photocurable materials.

A Novel Method of Incorporating CNT into Additive Manufacturing Electronics Dielectric Material

Flexible Hybrid Electronics (FHE) Parts that are additively manufactured give engineers and designers greater flexibility in geometry, complexity, and variety or customizability. In this work, UV curable dielectric materials for additive electronics and incorporated Carbon Nano Tubes (CNTs) within a formulated UV/LED curable matrix was used. It will be shown that inkjet printing CNT mixture in specific manner with a commercial UV curable dielectric improves mechanical and thermal properties of the final dielectric compared to the dielectric without the CNT mixture, including a significant decrease in the coefficient of thermal expansion, while keeping excellent electrical properties.

High Hydrophilic and Antibacterial Efficient UV-Curable Silicone-Containing Choline Chloride Quaternary Ammonium Salts Functionalized Materials.

Antibacterial materials with high hydrophobicity have drawbacks such as protein adsorption, bacterial contamination, and biofilm formation, which are responsible for some serious adverse health events. Therefore, antibacterial materials with high hydrophilicity are highly desired. In this paper, UV-curable antibacterial materials are prepared from silicone-containing Choline chloride (ChCl) functionalized hyperbranched quaternary ammonium salts (QAS) and tri-hydroxylethyl acrylate phosphate (TAEP). The materials show high hydrophilic performance because their water contact angle is as low as 19.3°. The materials also exhibit quite high antibacterial efficiency against S. aureus over 95.6%, fairly high transmittance over 90%, and good mechanical performance with tensile strength as high as 6.5MPa. It reveals that it is afeasible strategy to develop antibacterial materials with low hydrophobicity from silicone-modified ChCl-functionalized hyperbranched QAS.

Development of SiO2 UV-curable materials and their fine-patterning using sol-gel method

Development of SiO2 UV-curable materials and their fine-patterning using sol-gel method

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°.

Investigation of biosensing properties in magnetron sputtered metallized UV-curable polymer microneedle electrodes

Direct management and assessment of metal film properties applied to polymer microneedle (MN) biosensors remains difficult due to constraints inherent to their morphology. By simplifying the three-dimensional structure of MNs and adjusting the deposition time, different thicknesses of Au films were deposited on the UV-cured polymer planar and MN substrates. Several properties relevant to the biosensing of the Au films grown on the polymer surfaces were investigated. The results demonstrate the successful deposition of pure and stable Au nanoparticles onto the surface of UV-curable polymer materials. Initially, Au islands formed within the first minute of deposition; however, as the sputtering time extended, these islands transformed into Au nanoparticle films and disappeared. The hydrophilicity of the surface remains unchanged, while the surface resistance of the thin film decreases with increasing thickness, and the adhesion to the substrate decreases as the thickness increases. In short, a sputtering time of 5–6 min results in Au films with a thickness of 100–200 nm, which exhibit exceptional comprehensive biosensing performance. Additionally, MNs made of Au/UV-curable polymers and produced using magnetron sputtering maintain their original shape, enhance their mechanical characteristics, and gain new functionalities. The Au/UV-curable polymer MNs exhibited remarkable electrode performance despite being soaked in a 37 °C PBS solution for 14 days. These discoveries have important implications in terms of decreasing the dependence on valuable metals in MN biosensors, lowering production expenses, and providing guidance for the choice and design of materials for UV-curable polymer MN metallization films.

In-situ swelling of pH-responsive microgel particles during photopolymerization to mitigate shrinkage stress of UV-cured materials

This paper utilizes a soap-free emulsion polymerization process to prepare microgel particles that can swell in response to in-situ generated acid in photocurable resin. By controlling the type and concentration of end-capping agents and the content of cross-linking agents, pH-responsive microgel particles with significantly increased particle size in acidic environments are synthesized. The strong protonic acid generated by the photoacid upon exposure to ultraviolet light can reduce the pH of the UV-curable resin, leading to an enlargement of the particle size. This can compensate for the volume shrinkage of the resin, ultimately reducing shrinkage stress. The research findings indicate that the addition of 5 wt% of pH-responsive particless and 2 wt% of photoacid to the UV-curable resin results in a reduction of approximately 40% in shrinkage stress and shrinkage rate.

Adjustable comb/bottlebrush fast UV-curable epoxy-based form-stable phase change materials with high encapsulation rates and ultralow enthalpy loss

The design strategy of reliable epoxy-based FSPCMs with fast UV-curable performance or self-healing behavior.

Low volume shrinkage, high bio-based, and UV-curable coatings from castor oil-based reactive diluent via a one-step reaction

UV-curing technology possesses the advantages of fast curing, and cured at room temperature, which has been developed rapidly in recent years. However, the volume shrinkage usually occurs during the UV-curing polymerization process, seriously hindering its application. In this paper, a low volume shrinkage, high bio-based contents, and UV-curable resins was fabricated from the raw materials of castor oil, and cardanol. A three functional castor oil-based reactive diluent (COSH) was synthesized using a one-step method of thio-ene click reaction, and the COSH was blended with cardanol-based PUA (CNPUA) oligomer with different content, and prepare bio-based UV-curable materials. The comparative investigation were conducted on the thermal, and mechanical properties with petroleum-based diluents of trimethylolpropane triacrylate (TM), and trimethylolpropane tris (3-mercaptopropionate) (TMSH), respectively. As the content of COSH increased to 40%, the bio-based content of the CNPUA/COSH reached to the highest value of 60.0%, and the viscosity and volume shrinkage of CNPUA/COSH exhibited the lowest data of 1651 mPa·s, and 13.3%, respectively. The COSH not only had good dilution ability, but also possessed excellent anti volume shrinkage ability, and the mechanism of the anti shrinkage COSH was also explored. In addition, the three long carbon chain structures of the COSH endowed the cured coating excellent adhesion of 1 level, and pencil hardness of 3 H-4 H, as well as the flexibility of 2 mm. Lastly, the kinetics of the resulting resins were studied using real-time infrared spectroscopy (RT-IR). This study provides a feasible method for preparation of oil-based reactive diluents, and a new strategy for constructing the sustainable UV-curable materials with high performance.

Efficient reduction of photopolymerization shrinkage stress through microporous particles templated from Pickering emulsion droplets

Photopolymerization of acrylate based resin is a rapid, efficient and low-energy curing process that is achieving wide applications in many industrial fields. However, the volumetric shrinkage and the shrinkage stress of the cured resin have long been the major factor reduces adhesion strength of UV curable coatings onto the substrate. In this paper, the Pickering emulsion template method is employed to prepare elastic microporous particles with well-defined surface and internal structures and these microporous particles are thus added into the UV curable resin formulation to verify their capability to reduce polymerization stress through the microporous structure. The gel point time of UV-curable materials is delayed by 11 s with 1.5 wt% addition of the microporous particles and the double bond conversion at the gel point is subsequently increased. By real time MIR-photo-rheology and 3D line scanning laser confocal measurement, it is found that addition of microporous particles into the resin formulation can reduce the volume shrinkage of the resin by 61.2 % with only 1.5 wt% microporous particles, while the excellent mechanical and thermal properties of the cured resin is basically maintained.

Research Progress of Self-Healing Polymer for Ultraviolet-Curing Three-Dimensional Printing.

Ultraviolet (UV)-curing technology as a photopolymerization technology has received widespread attention due to its advantages of high efficiency, wide adaptability, and environmental friendliness. Ultraviolet-based 3D printing technology has been widely used in the printing of thermosetting materials, but the permanent covalent cross-linked networks of thermosetting materials which are used in this method make it hard to recover the damage caused by the printing process through reprocessing, which reduces the service life of the material. Therefore, introducing dynamic bonds into UV-curable polymer materials might be a brilliant choice which can enable the material to conduct self-healing, and thus meet the needs of practical applications. The present review first introduces photosensitive resins utilizing dynamic bonds, followed by a summary of various types of dynamic bonds approaches. We also analyze the advantages/disadvantages of diverse UV-curable self-healing polymers with different polymeric structures, and outline future development trends in this field.

Polyfunctional phytic acid-based reactive diluent for UV-curable coating with improved flame-retardant performance and toughness

The shortcomings of oligomer resin, including its high viscosity, easy brittleness and lack of flame-retardant performance, obviously limit the application fields of the related coatings. Herein, a UV-curable polyfunctional biomass-based diluent (PAGMA) is conveniently and effectively synthesized by grafting glycidyl methacrylate onto phytic acid. The structural characterization of PAGMA is identified by FT-IR and 1H NMR tests. Moreover, PAGMA diluent is mixed with UV-curable epoxidized soybean oil-based acrylic resin (ESO-based resin), and the influences of PAGMA on the viscosity of ESO-based resin, the mechanical property and the flame-retardant efficiency of the related films are systemically researched. All results demonstrate that the viscosity of composite resin (R2 resin) with 20 wt% PAGMA reduces by 39.2% compared with that of ESO-based resin. And the toughness of the cured film (F2 film) prepared by R2 resin achieves about 1.18 MJ·m-3, which is 2.26 times as large as the cured film prepared without PAGMA (F0 film). Furthermore, the limiting oxygen index value of F2 film improves by 31.2% compared with that of F0 film, and the F2 film can self-extinguish after being ignited. Thus, the prepared polyfunctional biomass diluent can be applied to UV-curable coatings to decline the coating viscosity and enhance the comprehensive properties of coating films, which assists in broadening the application fields of UV-curable materials, especially in fire prevention.

Investigation of cottonseed oil as renewable source for the development of highly functional UV-curable materials

Containing unique combinations of triacylglycerols, plant oils derived from different sources, have a great potential to be used in various area of applications. Nowadays, among all of oils, soybean oil, which is also being used as food source, is the most explored in research for industrial uses. At the same time, other types of oils have been studied not nearly as much as soybean oil. This study explores the utilization of a cottonseed oil for the development of a bio-based UV-curable polymer resin. Since the fatty acid composition of cottonseed oil is very different compared to soybean oil, the products from this oil can be beneficial in entirely different applications. The combination of cottonseed oil as a raw material and the ultraviolet (UV) process as a curing technology presented in this work, provides an alternative “greener” solution for problems industry is facing. Acrylated-epoxidized cottonseed oil (AECO) was synthesized by the epoxidation of cottonseed oil via the peracetic acid method, followed by the acrylation of the epoxidized oil using acrylic acid. This polymer resin then was used as a main component in formulations and transformed into a crosslinked network by photopolymerization. In order to achieve the desired mechanical properties of the plant oil-based films, two reactive diluents, 1,6-hexandioldiacrylate and trimethylolpropane triacrylate, in different weight ratios were added separately to the formulations. The properties of the coatings, as well as their thermal and mechanical stability were evaluated. Moreover, comparing the AECO resin with an already existent commercially available product, the potential industrial use of AECO was assessed. In general, the results highlight increased flexibility of AECO-based materials compared to petroleum-derived ones, which is beneficial for many applications, including, but not limited to wood substrates, printed electronics, paper products. The study concluded that functionalized resins obtained from cottonseed oil can provide a competitive and sustainable alternative to accommodate the rapid growth in the use of bio-based UV-curable materials.

Fabrication of peristaltic electromagnetic micropumps using the SLA 3D printing method from a novel magnetic nano-composite material

Micropumps are one of the main components of microfluidic systems that play an essential role in the development of these systems. They are responsible for the fluid movement inside the microfluidic systems. In this paper, three electromagnetic micropumps with single, double, and triple chambers fabricated using the stereolithography (SLA) 3D printing method from a novel UV-curable magnetic nanocomposite material are presented. The components of this micropump include nozzle-diffuser microchannels, a chamber, a flexible magnetic membrane, and a micro-coil. To determine the characteristics of the proposed micropumps, the effect of the electric current signal and its patterns and magnetic field strength on the temperature changes, magnetic nanoparticle concentration on the membrane displacement, and flow rate of the micropump have been investigated. The micropump membrane with 5 wt% nanoparticles concentration can achieve a displacement of 65 µm for an electric current of 1000 mA in 12 s. The highest fluid flow rate of single, double, and triple chamber micropumps are 78, 316, and 600 nL/s, respectively, at an electric signal with a period of 8 s and a duty cycle of 60%.

Fabrication and performance of fast and reusable pH-sensitive UV-curable silicone modified materials

Determination, control and monitoring the pH valve are quite important for many fields, especially for monitoring the wastewater discharged from chemical industry. Fast and reusable pH-sensitive ultraviolet (UV)-curable silicone modified materials with a visible color change in pH conditions of 9.5–14 were prepared by UV initiated thiol-ene reaction with vinyl containing silicone-modified hyperbranched polymers with phenolphthalide (PHP) substitutes and thiol silicone resin. It demonstrated that the UV-curable materials are with transparency higher than 90 %, pencil hardness of F-8 H and Td5 in the range of 310–338 °C. The UV-curable materials exhibited an outstanding pH-sensitive property, and they can be used repeatedly about 400 cycles without a faded change of color and loss of sensitivity. What's more, it is interesting when pH value is in the range of 9.5–14, the materials can recognize the organic solvents with different pH values and different volume percentages. The mechanism for the pH-sensitive property was proposed. These materials have potential applications for fabrication quick, reusable and real-time monitoring pH-sensitive devices for alkaline wastewater.

Influence of glass fiber on mechanical properties of UV-cured lining materials

Glass fiber is an important component of resin composites and greatly affects the properties of materials. UV-cured pipe rehabilitation lining materials prepared by hand lay-up process using glass fibers with different areal densities and weaving types were studied in this paper. Their thermal stability and mechanical properties, such as flexural strength, flexural modulus, and tensile strength, were studied. The results show that the glass fiber-reinforced UV-cured lining material has good thermal stability at 300°C. With the glass fiber areal density increase, the lining material’s flexural strength, and modulus increase. Compared with the plaid stitch-bonded felt and the plaid lapped felt, the higher degree of bonding between warp-knitted stitch-bonded felt and resin can significantly improve the flexural strength and tensile strength of the lining material.

Study on the curing process and thermal performance of an RDX-based UV-cured combustible ordnance material

RDX-based combustible ordnance material was prepared using a 3D printer, and the curing process of the UV-curing resin (acrylic resin) was tracked by infrared spectroscopy. The thermal decomposition characteristics of photocurable combustible materials were studied by DSC, and the non-isothermal method was used to study Kinetic parameters. Meanwhile, the delayed ignition time of UV-cured combustible materials at different temperatures were tested using a muffle furnace. Infrared spectroscopy test results show that the C=C bond conversion rate can reach to 81.7% when the acrylate resin is irradiated for 2 s. DSC test results show that the thermal decomposition peak temperature of the UV-curing combustible ordnance material is 235.9°C (at heating rate of 10°C/min), and the activation energy of the reaction is 129.93 kJ/mol. The critical explosion temperature and spontaneous temperature were 466.85K and 469.31K, respectively.

Arkema Partners with Research Institute to Open a Lab for Next-Generation UV-Curable Materials

Arkema Partners with Research Institute to Open a Lab for Next-Generation UV-Curable Materials