Urethane Acrylate Research Articles

Influence of Solid Lubricants on the Tribological Performance of Photocurable Resins for Vat Photopolymerization

New developments in additive manufacturing (AM) are enabling the use of 3D printed parts in increasingly demanding applications, such as in mechanical power transmission systems, where excellent build quality and tribological performance are required. The tribological properties of thermoplastic-based AM technologies are well knowninject, whereas the performance of photopolymer-based AM technologies is very rarely explored. This study aims to provide new insight into the tribological performance of 3D printed parts produced using vat photopolymerization (VPP). Photocurable resins based on aliphatic urethane acrylate oligomers were modified with different solid lubricants (polytetrafluoroethylene (PTFE), graphite and molybdenum disulfide (MoS2)) and 3D printed using Digital Light Processing (DLP). The mechanical and thermal properties were studied using the tensile tests, Charpy impact tests, Shore D, and dynamic mechanical analysis (DMA). The tribological performance was studied using a Pin-on-Disk tribometer. Among the lubricants, PTFE had the highest impact on the coefficient of friction (µ) and the specific wear rate (ws). The hybrid lubricant system (PTFE/MoS2) resulted in excellent tribological performance, where the µ was reduced by up to 52% and ws by up to 92%.

Experimental study of lateral resistance of bolted joints using Japanese cedar (Cryptomeria japonica) treated with resin impregnation

The development of wooden joints possessing high resistance performance has become an important issue for the construction of newer buildings. This study attempts to strengthen the lateral resistance of bolted joints using the previously reported plasticizing technique. This technique consists of two processing stages: incising the surface of the wood using an ultraviolet wavelength short-pulse laser and impregnating the resin into the incised area. This technique makes it possible to plasticize only a local part of the wood surface. Bolted joint specimens were assembled using plasticized wood around the bolt hole, and the lateral tests were conducted. Acrylic monomer and urethane prepolymer were used as the impregnating resins and their incision depths were set as 4 and 10 mm. When the lateral load acted parallel to the grain, changes in the lateral resistance characteristics were observed, especially for the stiffness and yield load. For example, when acryl was used, and the incision depth was 10 mm, an increment of 73% in the yield load was observed, as compared to the non-impregnated specimens. The specimen groups impregnated with acryl exhibited greater changes in their properties than those using urethane. When loaded perpendicular to the grain, an increase in properties were observed; however, these increments were lower than those of the groups loaded parallel to the grain.

Structural composite laminate materials with low dielectric loss: Theoretical model towards dielectric characterization

Organic matrix composite materials exhibit high mechanical properties associated with lightweight. They also provide the ability to embed radiofrequency features, such as microwave antennas, for smart load-bearing structures of various means of transport. Antennas implementation into composite panels requires electrically conductive fabrics for the radiating elements, feeding lines and ground planes embedded into the structural dielectric composite materials with low loss at microwaves. Accordingly, the present study investigates the assessment of the dielectric characteristics, namely the relative permittivity εr and the loss tangent tanδ of composite laminate materials made of E-glass, S2-glass and quartz fabrics infused with epoxy, polyester and urethane acrylate thermosetting resins. The related dielectric characteristics, measured in two operating bands, namely 100 MHz to 1 GHz and 18–26 GHz, are compared with the theoretical values computed from the 2D Maxwell-Garnett model that we have adapted to laminate composite materials. Mechanical characteristics of such composite laminate materials are also investigated. Eventually, the quartz/urethane acrylate laminate is highlighted as a low loss composite material, highly suitable for the fabrication of antennas operating at microwaves.

Improving the Efficiency of a Polymer Nanocomposite for Formation of Photon Structures by Means of Optical Recording

We present the results of investigation of conditions leading to optimization of an optical recording medium based on photosensitive urethane–acrylate nanocomposites containing silicone oxide nanoparticles that is used for efficient recording of Bragg gratings by means of multiple-beam interference. It is demonstrated that the choice of most efficient monomers and their concentration in the nanocomposite depending on their structure and the rate of polymerization, followed by finding optimal intensity of recording radiation for given composition, allows regulating the conditions for component diffusion thereby optimizing their redistribution in the recording medium and formation of regions with different values of refractive index. The results of the study can be used for creation of complex 2D and 3D photonic structures based on purposeful modification of light-sensitive polymer nanocomposites exhibiting various properties (luminescent, nonlinear-optical, etc.)

Facile synthesis and characterization of renewable dimer acid-based urethane acrylate oligomer and its utilization in UV-curable coatings

A UV-curable polyurethane acrylate (PUA) oligomer was prepared from dimer acid (DA) based polyester polyol (DAPEP) with a monofunctional acrylate precursor which was developed upon isophorone diisocyanate (IPDI) reacted with 2-hydroxyethyl methacrylate (HEMA). The structural elucidation of synthesized dimer acid based PUA (DAPUA) oligomer was verified through Fourier-transform infrared spectroscopy (FT-IR) and Proton nuclear magnetic resonance (1H NMR). A series of UV cured coatings were prepared by adding trimethylolpropane triacrylate (TMPTA) and 1,6-hexanediol diacrylate (HDDA) reactive diluents in varying percentages (10−30 wt%) to PUA oligomer. The bio-coatings exhibited exceptional results, including the highest thermal degradation temperature of 382–422 °C, glass transition temperature (Tg) of 56.38–66.27 °C, the tensile strength of 17.3–30.6 MPa, volume shrinkage of 6.19–9.13 %, and surface roughness of 4.89–28.21 nm. Compared to vegetable oil based UV-curable coatings, long chain dimer acid based PUA oligomer coatings exhibited excellent flexibility, impact, hydrophobicity, and resistance to volume shrinkage.

Flexible, polymer-supported, ZnO nanorod array photoelectrodes for PEC water splitting applications

An innovative ZnO based flexible photoelectrode was prepared on the micropatterned poly (urethane acrylate) (PUA) for efficient photoelectrochemical water splitting application. The micropatterned PUA was fabricated by the mold transfer process. A thin layer of Indium Tin Oxide was deposited on the PUA surface to give it surface conductivity and subsequently, one dimensional ZnO nanorods (NRs) arrays were prepared by a facile seed layer and hydrothermal method. The photocurrent density of the photoanode of ZnO NRs arrays deposited on the micropatterned PUA (ZPM) was ~0.52 mA cm−2 at 1.23 V vs. RHE, which was ~3 times higher compared to that of ZnO NRs arrays deposited on the flat PUA (ZPF). The improved performance of the ZPM photoanode was attributed to the enhanced light capture capacity, excellent carrier collection ability, lower charge transfer resistance, and higher electrochemically active surface area.

Ultrasensitive temperature sensor based on a urethane acrylate-coated off-axis spiral long period fiber grating

We propose and experimentally demonstrate an ultra-high sensitivity fiber-optic sensor to measure temperature changes in order to establish a high-precision temperature model in the bio-fermentation process. The proposed sensor based on off-axis spiral long-period fiber grating (OAS-LPFG) is fabricated in a single mode fiber (SMF) by arc discharge technology. This kind of grating is distinguished in the refractive index (RI) modulation, geometry changes, and shear stress of a spiral structure. Because the RI of the urethane acrylate is close to that of the SMF cladding and has a high thermo-optic coefficient, the resonant wavelength of the OAS-LPFG dip has a high sensitivity to the temperature measurement. The response of the OAS-LPFG to environmental RI is analyzed by full vector complex coupling mode theory. In the experiment, the temperature sensitivity of the proposed sensor can be reached ∼-108.69 nm/°C over a range of 25.0 °C to 25.5 °C. Compared with other all-fiber-based temperature sensors, the sensor has higher sensitivity.

Polymerizable Hydrophobically Modified Ethoxylated Urethane Acrylate Polymer: Synthesis and Viscoelastic Behavior in Aqueous Systems

Hydrophobically modified ethoxylated urethanes (HEURs) comprising hydrophilic poly(ethylene glycol) backbone and hydrophobic end groups are widely applied as rheological additives to regulate the viscoelastic behavior of waterborne systems such as coatings and inks. However, the conventional HEURs are usually nonreactive and remain free in final films, which may bring some defects and damages to the final cured films during the service time. An appealing way to improve filming properties may be to design reactive HEURs, which can participate in the post-crosslinking reactions with other components in formula during the film curing. In this work, a polymerizable acrylic-type HEUR (acrylic-HEUR) end-functionalized by the reactive methacrylate group and hydrophobic octadecyl tail is reported. The typical free radical polymerization feature of acrylic-HEUR based on the highly reactive methacrylate group is carefully clarified by dynamic light scattering, in situ nuclear magnetic resonance (1H NMR), and rheological measurements. The excellent thickening performance of acrylic-HEUR in waterborne UV emulsions and its effective copolymerization reactivity with the UV-curable matrix resin are demonstrated by in situ rheological measurements under UV irradiation in detail. Compared to conventional nonreactive HEURs, the copolymerization reactivity of acrylic-HEUR may make it especially suitable for applications in waterborne UV coatings to avoid its migration from final UV-cured films. This work may not only open a new perspective for the fabrication of HEUR polymers with high chemical reactivity but also promise the potential of polymerizable HEURs as superior associative thickeners in industry.

Highly Flexible Superhydrophobic Poly(Urethane Acrylate) Film for Applications Requiring High Optical Transparency

AbstractThe present work elucidates the successful attempts toward the development of a highly transparent, flexible, and superhydrophobic (HTFS) film. The HTFS film is obtained by introducing graphene oxide (GO) into micropillar‐patterned poly(urethane acrylate) (PUA), followed by siloxane functionalization via chemical vapor deposition. The fabricated SPG2 film (siloxane‐functionalized PUA incorporated with 0.1 wt% of GO) exhibits a water advancing contact angle, water receding contact angle, and sliding angle of 155.5 ± 0.3°, 143.4 ± 0.6°, and 9 ± 0.4°, respectively. The SPG2 film also exhibits an optical transmittance of ≈84% at 550 nm. Mechanical wearable tests demonstrate no significant degradation in the self‐cleaning properties and optical transparency. The fabricated HTFS film (SPG2) is used as a protective layer for a solar module. This solar module shows improved power conversion efficiency (PCE) compared to that of a bare solar module owing to the high optical transparency and light‐trapping effect of the fabricated film that reduce the light reflectance. Furthermore, the SPG2‐protected solar cell demonstrates superior PCE under different surface contamination conditions comparing to other cells. The fabricated micropatterned SPG2 film can be used for various outdoor applications that require high optical transparency, flexibility, and superior self‐cleaning performance.

Preparation and properties of UV-curable polyurethane-acrylate coatings of pre-coated metal (PCM): effect of polyol type/contents on adhesive property

Since UV curing coatings form a coating film with low adhesive property, it is difficult to use it as a coating for pre-coated metal (PCM) of post-processing method which has been actively studied recently. In this study, to apply UV-curing type coatings to pre-coated metal (PCM), which is applied as a method to improve productivity and to shorten the coating process, urethane acrylate oligomers were synthesized by using the content of polycaprolactone diol and hydrogenated polybutadiene glycol as a soft segment. UV-curable polyurethane acrylate coatings were prepared by varying the kind and content of the reactive diluent (IBOA, TMPEOTA). The urethane-acrylate oligomer and the coatings were well-prepared and confirmed using FT-IR. The storage modulus at RT, tensile strength and modulus were the highest values and the elongation at break was low. Also, as TMPEOTA content increased, the Tg of hard segment and storage modulus at RT, tensile strength and modulus increased, but elongation at break decreased. The surface free energy of all coating films was lower than that of metal plate. And the adhesive property of coatings using HPBD polyol of 30 and 50 mole% was the best and pencil hardness was also high in these coatings. MEK rubbing was increased with the increase of HPBD polyol and TMPEOTA content.

Synthesis of UV Curable, Highly Stretchable, Transparent Poly(urethane-acrylate) Elastomer and Applications Toward Next Generation Technology

Here, highly stretchable and transparent UV curable poly(urethane-acry-late) elastomer has been synthesized by reacting urethane acrylate oligomer and two reactive diluents monomers. The synthesized elastomers can be stretched up to 600% and have high transparency of over 90% transmittance. The synthesized elastomers have been applied to several applications. Simple 3D model was printed with a 3D printer on the market. Stretchable ionic conductors were fabricated by a facile method of adding salt with ionic conductivity. Similarly, the resin with β-cyclodextrin, a cage-structured molecule, was cured and foam was generated simultaneously under the UV radiation. This research paves a new way for further development in applications of UV curable transparent elastomer and 3D printable elastomeric material.

Synthesis and Formulation of PCL-Based Urethane Acrylates for DLP 3D Printers.

In this study, three PCL-based polyurethane acrylates were synthesized and further formulated into twelve resins for digital light processing (DLP) 3D printing. Three PCL diols with different molecular weights were synthesized via ring-opening reaction of ε-caprolactone on diethylene glycol, with the catalyst stannous octoate. Isophorone diisocyanate (IPDI) was reacted with 2-hydroxyethyl acrylate (2-HEA) and the PCL diols form PCL-based polyurethane acrylates. Twelve resins composed of different percentages of PCL-based polyurethane acrylates, poly (ethylene glycol) diacrylate (PEGDA), propylene glycol (PPG) and photo-initiator were further printed from a DLP 3D printer. The viscosities of twelve resins decreased by 10 times and became printable after adding 30% of PEGDA. The degree of conversion for the twelve resins can reach more than 80% after the post-curing process. By changing the amount of PEGDA and PPG, the mechanical properties of the twelve resins could be adjusted. PUA530-PEG-PPG (70:30:0), PUA800-PEG-PPG (70:30:0), and PUA1000-PEG-PPG (70:30:0) were successfully printed into customized tissue scaffolds. Twelve PCL-based polyurethane photo-curable resins with tunable mechanical properties, cytotoxicity, and degradability were successfully prepared. With the DLP 3D printing technique, a complex structure could be achieved. These resins have great potential for customized tissue engineering and other biomedical application.

APPLICATION OF DYNAMIC MECHANICAL ANALYSIS FOR UV-CURED COATINGS

The present study is about soya epoxy ester which was made by epoxy resin and fatty acid. Oleochemical polyols were prepared after the soya epoxy ester reacted with various hydroxyl and cellulose based derivatives. These oleochemical polyols were changed to urethanes prepolymers by reacting NCO groups of TDI and IPDI. By utilizing the reaction of NCO end group of urethane with HEMA, these urethanes were transformed in to urethane acrylate oligomer. By mixing the oligomers with various reactive diluents, UV curable coating compositions were derived. The methodology was based on dynamic mechanical analysis. The UV cured samples from cellulose based oleochemical polyols exhibit good mechanical and thermal properties. Their mechanical properties are more dependent on double bonds from unsaturated contribute to curing with extra cross-linking by an oxidative mechanism.

Catalytic effects of zirconium on scratch-healing and mechanical properties of urethane–acrylate automotive clearcoat

This work describes the effect of zirconium(IV) acetylacetonate (Zr(acac)4) on the self-healing and thermomechanical properties of urethane–acrylate copolymers, and which were compared with dibutyltin dilaurate (DBTDL). For prepolymer synthesis, glyceryl methacrylate (GlyMA) and 2-hydroxyethyl methacrylate (HEMA) were chosen and copolymerized with methyl methacrylate (MMA) and butyl acrylate (BA) at a concentration of 8 mol%. The prepolymers (G8 and H8) were then crosslinked with HDI trimer to prepare self-healing copolymers, and DBTDL or Zr(acac)4 was used as both crosslinking and self-healing catalysts. The self-healing performance of new carbonate bond formation by DBTDL and transesterification by Zr(acac)4 were studied and compared using single scratch test with atomic force microscopy (AFM). Owing to the secondary hydroxyl groups of GlyMA, DBTDL shows scratch-healing capability only in the GlyMA-based copolymer (G8) within 1 h at 55 and 75 °C. On the other hand, Zr(acac)4 shows scratch-healing capability in both copolymers (G8 and H8) within 1 h at 55 and 75 °C; however, transesterification may result in the changes of storage modulus and glass-transition temperature (Tg). This was confirmed from dynamic mechanical analysis (DMA) that a low temperature (∼55 °C) exhibited excellent self-healing performance with minimal hardness change by transesterification.

Evaluation of Adhesion of Polymer Composite Coatings

Thin film coatings on fingernails and toenails are used for aesthetic reasons or to strengthen fragile nails. Coating disintegration is one of the most important characteristics of short-term coatings. The aim of this research was to investigate adhesion test methods for UV-cured urethane acrylate coatings. Coatings was compared evaluating gel fraction and degree of conversion of C=C bonds. Adhesion was measured using pull-off adhesion test and coating removability was evaluated after coating soak-off in solvent media with cross-cut tester. Systems with four different monomers in two concentrations was evaluated. All systems show a strong correlation of adhesion with the time of disintegration.

The role of rutile TiO2 nanoparticles on weathering resistance of photocurable acrylate urethane coating

AbstractThe aim of this paper is to evaluate the role of nano rutile TiO2 (R‐TiO2) on the weathering resistance of UV curable acrylate urethane coating. At first, the nano R‐TiO2 at the content of 2 wt.% was dispersed in 1,6 Hexanediol for 3 hrs and then mixed with the urethane acrylate Eberyl 284 (E284) and photo initiator Irgacure 184 (I.184) for 30 min. After UV curing in FUSION UV equipment for 4.8 s, the coating unreinforced and reinforced 2 wt.% nano R‐TiO2 were analyzed by FE‐SEM in order to determine the dispersion of the nanoparticles in the polymer substrate and examined the accelerated aging in an Atlas UV/CON chamber. The aging of the coatings was assessed by IR analysis and measuring the losses of their weight and mechanical properties. The obtained results showed that the nanoparticles were distributed evenly in polymer substrate with the size of 50‐150 nm. In the presence of 2 wt.% R‐TiO2 nanoparticles, the acrylate urethane/R‐TiO2 nanocomposite coating was more weather durable than the neat coating (without the nanoparticles). After 48 aging cycles, the CH and CNH groups, the weight and the abrasion resistance of the nanocomposite coating slightly decreased, whilst those of the neat coating was severely degraded.

Optical and encapsulation properties of La(OH)3/poly(urethane acrylate) composites

Two lanthanum hydroxide (LH, La(OH)3) materials, i.e., La(OH)3 submicroplates (LHSMPs) and La(OH)3 nanoparticles (LHNPs), were synthesized hydrothermally, and their optical and encapsulation properties were investigated. The surfaces of the LHSMPs and the LHNPs were modified with a coupling agent: [3-(methacryloyloxy)propyl] trimethoxysilane (MPS). To prepare transparent encapsulation composite materials, both types of surface-modified particles were dispersed in a poly(urethane acrylate) (PUA) adhesive polymer binder. The composite film with surface-modified LHNP-PUA exhibited better optical properties (higher transmittance and lower haze) than that with surface-modified LHSMP-PUA owing to smaller particle size. However, the latter was observed to be more advantageous for preventing the permeation of water molecules owing to the larger particle size.

Development of a multi-functional acrylic urethane coating with high hardness and low surface energy

This study developed multi-functional acrylic urethane coating materials with anti-graffiti, anti-contamination, and anti-adhesion properties. The newly-developed coating was synthesized by high glass transition temperature (Tg) acrylic polyol and low-viscosity single-end-type silicone oil. The coating materials were chemically bonded and reacted with isocyanate to form acrylic urethane. The hardness, surface energy, color difference value, and anti-adhesion properties were examined using nanoindentation, a contact angle analyzer, a color difference meter, and a universal tensile test machine, respectively. In addition, the degradation of the coating was evaluated using an accelerated weathering test, taking into account various degradation factors (UV, humidity, high temperature, and water). In general, the properties of the coating degraded due to the loss of silicone oil after the accelerated weathering test. However, the degradation was retarded when high Tg acrylic polyol and low-viscosity single-end-type silicone oil were chemically bonded. The newly-developed multi-functional acrylic urethane coating exhibited long-term stability against an accelerated weathering test of 120 h. The developed coating will be useful in broad applications, including harsh environments such as underground walls, heritage, facilities, and subways.

The Role of POSS Functionality on Induced Deviation of Nano and Micromechanical Properties of UV Curable Urethane Acrylate Nanocomposite Coatings

The inorganic-organic hybrid coatings based on UV curable urethane acrylate contained two types of polyhedral oligomeric silsesquioxane (POSS) were prepared. The hydroxyl functionalized POSS nanoparticles, pristine POSS, and the one modified by acrylic acid utilized to study the effect of nanoparticle content and its functionality on ultimate mechanical properties of the hybrid coatings. The nanomechanical properties and scratch resistance of nanocomposite coatings were evaluated with nanoindentation and nanoscratch techniques, respectively. Consequently, the results compared with previously obtained DMTA data. The results revealed that by embedding acrylic acid modified POSS, the surface hardness and elastic modulus improved. Further increasing acrylic acid modified POSS content to 5%, the surface elastic modulus and hardness improved to 37% and 35%, respectively, relative to neat coating and also the enhanced scratch resistance was observed. Furthermore, the discrepancy between the surface elastic modulus and bulk elastic modulus was rationalized and the contributed parameters that led to this deviation such as pile-up area, holding time and hydrostatic stress was investigated. The results showed that apart from the inefficiency of Oliver and Pharr method to precisely evaluate the nanomechanical properties of hybrid coatings, the targeted placement of POSS nanoparticle is responsible for this disparity between surface mechanical properties and its bulk values.

Influence of organic UV absorber on the accelerated weathering stability of UV curing coating based on acrylate urethane resin

AbstractThe purpose of this paper is to evaluate the photoprotective efficiency of organic UV absorber Tinuvin 384 (T384) on the photocurable acrylate urethane coating under the accelerated weathering condition. The coatings without and with 2 wt.% T384 were examined by UV/CON accelerated weathering testing device. The aging of the coatings was assessed by IR and FE‐SEM analysis as well as the measurement of mechanical and weight loss. The obtained results showed that due to the photoprotection of T384, the urethane acrylate coating was stable under the effect of accelerated weathering factors. After 48 cycles of aging, the CH and CNH groups, the abrasion resistance and the weight of the paint films containing 2 wt.% T384 were slightly decreased. Its surface was damaged just a little, while that of the coating without T384 was severely degraded.