Acrylic Polyurethane Coatings Research Articles

Synthesis and characterization of ureidopyrimidinone-functionalized polyurethane acrylates and their hybrid nanocomposites for UV coating applications

In this study, ureidopyrimidinone moieties (UPy), capable of physical crosslinking via quadruple hydrogen bonding, were successfully incorporated into UV-curable polyurethane acrylate prepolymers. First, a hydroxyl-terminated unsaturated ester monomer was synthesized and reacted with isophorone diisocyanate to create a hydroxyl-terminated UV-curable urethane oligomer (U–OH). Then, isocyanate-terminated building blocks (UPy moieties and an acrylate-based photosensitive monomer) were synthesized and used in various ratios to functionalize U–OH for the preparation of a series of UV-curable UPy-containing polyurethane acrylate (PUA) resins. The resulting products were structurally characterized using 1H NMR and FTIR spectroscopy. Furthermore, organic–inorganic hybrid nanocomposites were obtained by introducing silane coupling agents into PUA resins using the sol–gel process. A series of UV-curable UPy-containing PUA coatings and hybrid nanocomposites were prepared, and their synergistic effect on coating properties was investigated. The dynamic mechanical analysis revealed that the Tg of the samples increased with increasing UPy content, although the mechanical properties remained largely unaltered, as shown by the stress–strain test. The studies also demonstrated that the hybrid nanocomposites exhibited higher decomposition temperatures and better thermal stability compared to pure PUAs. All the coatings exhibited good transparency in the visible region. An optical microscope was used to investigate the self-healing property by scratching the plexiglass panels with a razor blade. Among the other samples, the coating with the highest percentage of UPy content exhibited the best self-healing ability after heat treatment at 90 °C for 10 min.Graphical abstract

Eliminating the oxygen inhibition in the redox free radical polymerization of alicyclic polyurethane acrylate coatings: A study of the beneficial effect of paraffin wax

Elimination of oxygen inhibition is still a challenge in the preparation of copolymers for steel bridge deck coatings industry by redox free radical polymerization (RFRP) technique in air and at room temperature. Herein, solvent-free paraffin wax composite alicyclic polyurethane acrylate (PW/APUA) coatings cured in air and at room temperature were developed by RFRP technique, and the efficacy and mechanism of oxygen inhibition elimination by paraffin wax during curing was investigated. The results of tensile, contact angle (CA) and water absorption (WA) tests showed that compared with pure APUA coating, the PW/APUA coatings exhibited superior mechanical properties and water resistance at room temperature, with tensile strength, elongation at break and CA up to 25.1 MPa, 204.23 % and 112.5°, respectively, and WA down to 0.008 %. Thermogravimetric analysis (TGA) suggested that the thermal initial decomposition of the coating increased from 180 °C to 200 °C after incorporation of paraffin wax. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) indicated that two glass transition temperatures of PW/APUA coating with 0.3 % paraffin wax were −88.4 °C and 92.6 °C, respectively. Moreover, microstructural characterization of PW/APUA coatings revealed that paraffin wax eliminated oxygen inhibition by forming a dense barrier layer on the air contact surface of the APUA coating. Furthermore, the paraffin wax molecules co-crystallized with the non-polar groups of acrylates, but did not form new chemical bonds. This study provides a distinct and general strategy for eliminating oxygen inhibition of RFRP technology in air.

Study on Press Formability and Properties of UV-Curable Polyurethane Acrylate Coatings with Different Reactive Diluents.

UV-curable coatings have numerous advantages, including environmental sustainability due to 100% solid content, economic feasibility attributable to relatively fast curing time, decent appearance, mechanical properties, chemical resistance, and abrasion resistance. However, UV-curable polyurethane acrylate coatings on metals apparently restrict their engineering applications owing to low mechanical properties and poor thermal stability, giving UV-curable coatings less flexibility and formability. In this study, we evaluated the property change of films according to the type of reactive diluents that lowers the viscosity of UV-curing coatings for pre-coated metal and has a substantial effect on the curing rate, viscoelastic properties, adhesive properties, and flexibility of the film. Moreover, there are many changes in the properties of coatings according to varied curing conditions in order to evaluate the oxygen inhibition phenomenon during the curing process in the atmosphere. In particular, to evaluate the effect of reactive diluents on forming formability, which is the most crucial property for the pre-coated metal, this study used conventional formability tests, such as t-bending or the Erichsen test. Moreover, a cross-die cup drawing mold with a similar form as failure and Safety Zone was utilized in order to obtain clearer information on its actual formability. The analysis on the effect of failure and safety zone on the material used in press forming was conducted by assessing limit punch height and forming a limit diagram of the manufactured film according to varied reactive diluents.

Multi-Perspective Evaluations of Laser-Removal Quality of Acrylic Polyurethane Coatings on Aluminum Alloy Substrate

Evaluation systems for objects after laser removal have not been systematically established, yet they have great significance for repairing engineering coating materials. In general, this paper mainly focused on the surface quality after laser removal, which was simulated by thermal models and characterized by microscopic, residual chemical compositions, and wettability. The laser removal threshold was considered to be a key indicator to regulate removal precision. Here, the thermal model was used to explore the threshold was 15 J/cm2, and the ablation P was 308 W at 100 kHz. Besides, the surface structure was observed through simulation before experiments. It also predicted the effect of laser power and overlapping on surface roughness, and therefore provided the theoretical reference for experiments. Then, two groups of samples were set up of the surface of acrylic polyurethane coatings on 2024 aluminum alloy with and without anodizing treatment, respectively. After the coatings were removed, microscopic morphologies demonstrated a wavy undulation structure with little residue. Meanwhile, the increments of roughness were less than 0.5 μm and the surfaces were with nice wettability. Evaluating the surface quality from the above aspects is meaningful and helpful for the non-destructive cleaning of aircraft skin coatings.

Nitrogen-Doped Graphene Sheets as Efficient Nanofillers at Ultra-Low Content for Reinforcing Mechanical and Wear-Resistant Properties of Acrylic Polyurethane Coatings

The enhancement of the mechanical and wear-resistant properties of polymer coatings plays a vital role for their application in hostile serving environments, and nanofiller is effective for this purpose. Herein, we systematically investigate a new nanofiller, nitrogen-doped graphene sheets (NGSs), which possess a multilayer sheet-like morphology and share a good compatibility with water. After the incorporation of NGS into a waterborne polyurethane (WPU), the mechanical and wear-resistant properties of NGS/WPU composite coatings significantly improve, and wear resistance behaves best at an ultra-low content, reaching up to 0.005 wt% (50 ppm). Furthermore, Young’s modulus is elevated by 52.67% and tensile strength is appreciably boosted by 58.87%. Simultaneously, an apparent reduction of weight loss of 78.74% is observed in the abrasion testing, and the ductility of NGS/WPU composite films is reduced by 48.38%. These make it possible that an ultra-low content of nanofiller efficiently reinforces polymer-based composites, with low cost in the wear-resistance related field.

Improved surface properties of a novel self-healing polyurethane-acrylate coating by in situ polymerizations of dihydroxy organo-montmorillonite on ancient wood

A novel polyurethane-acrylate (PUA) polymerized in situ with montmorillonite (MMT) was synthesized to improve the surface properties of self-healing coatings used for ancient wood. For better dispersion and interaction, natural MMT was initially modified to dihydroxy organo-montmorillonite (OMMT). The prepared self-healing PUA coatings were painted on ancient wood and the surface properties tested, characterized, and compared to pure PUA and natural MMT-added PUA. Those results showed that natural MMT was modified to dihydroxy OMMT by cation exchange. The dihydroxy OMMT was polymerized in situ during synthesis by reactions between OH and NCO groups. The PUA polymer incorporated within MMT to form an exfoliated structure. After painting ancient wood, the surface contained no obvious bulges and the roughness increased slightly. Due to OMMT addition, the adhesion and hardness of OMMT modified PUA increased to 1 class and 2H, respectively, which is acceptable for indoor woodenware. The abrasive resistance was also improved. Furthermore, dihydroxy OMMT promoted the self-healing of PUA. After 30 s of healing, damages disappeared.

Synthesis of Trivinylisooctyl POSS and Its Application in UV-Curing of Polyurethane Acrylate Coatings

To improve the overall performance of polyurethane acrylic (PUAs) coatings applied to an iron or wood substrate, a modifier, trivinylisooctyl polyhedral oligomeric silsesquioxane (TVi7iso–POSS), was successfully synthesized by a polycondensation reaction in the presence of an organotin catalyst. TVi7iso–POSS is a POSS derivative possessing three olefin and seven isooctyl bonds; its molecular structure was confirmed by FT-IR, 1H-NMR, and mass spectrometry. The synthesized TVi7iso–POSS was then used as a modifier with butyl methacrylate (BMA), dodecafluoroheptyl methacrylate (DFMA), difunctional PUA (PUA–2), and photo-initiator 1173 to produce a novel polyurethane coating (PFMPUAs) via UV-curing. The performance of the obtained PFMPUAs coating was analyzed via X-ray photoelectron spectrometry, SEM, atomic force microscopy, TGA, and differential scanning calorimetry. The newly synthesized modifier, TVi7iso–POSS, enhanced the thermal stability, hardness, flexibility, impact resistance, and adhesion of the PUAs coating and maintained its good light transmittance. Moreover, the PFMPUAs coating exhibited better overall performance compared to the previously studied PUAs coating when the addition of TVi7iso–POSS and DFMA was 15 wt.% of PUA–2. Therefore, the PFMPUAs coating has potential applications in the field of environmentally friendly coatings.

Nano-silica-containing acrylic polyurethane and acrylic-polyester hybrid polyurethane coatings for direct-to-metal (DTM) coating applications – a comparative study

Nano-silica-containing acrylic polyurethane and acrylic-polyester hybrid polyurethane coatings for direct-to-metal (DTM) coating applications – a comparative study

UV-cured electroactive polyurethane acrylate coatings with superhydrophobic surface structure of biomimetic peacock feather for anticorrosion application

In this work, UV-cured electroactive polyurethane acrylate (EPU) materials with the superhydrophobic surface structure of biomimetic peacock feather were firstly prepared and applied in anticorrosive coatings. Firstly, amine-capped aniline trimer (ACAT) and vinyl-capped aniline trimer (VCAT) were synthesised and characterised by 1H-nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR) and mass spectroscopy. Polyurethane acrylate (PUA) was synthesised and characterised by 1H NMR and FTIR spectroscopy. EPU was then prepared through the UV curing of PUA with 0, 1, 3 and 5 wt% VCAT (named EPU0, EPU1, EPU3 and EPU5, respectively) and characterised via FTIR. The redox capabilities of the as-prepared EPU series were investigated by cyclic voltammetry studies. EPU with higher VCAT loading (EPU5) exhibited better corrosion protection performance than those with lower VCAT loadings (EPU0, EPU1 and EPU3) based on a series of electrochemical corrosion measurements because of the formation of a dense metal oxide layer as evidenced by Raman spectroscopy. Moreover, EPU5 with the surface structure of biomimetic peacock feather (denoted by BEPU5) was prepared by nanocasting technique with polydimethylsiloxane as the flexible transparent negative template. The surface morphology and wettability of BEPU5 was investigated by scanning electron microscopy and contact angle (CA) analysis. The CA of BEPU5 remarkably increased to 145° compared with that of EPU5 63°. This massive increase in CA indicates efficient superhydrophobic properties, which were induced by the biomimetic peacock feather and produced outstanding corrosion protection performance for short and long terms based on a series of electrochemical corrosion measurements. This study is the first of its type to produce a biomimetic feather with massive increase in superhydrophobic properties, which is expected to revolutionise biomimetic industrial coating technologies towards better corrosion protective coatings.

UV-curable self-matting waterborne polyurethane acrylate coating via self-wrinkled surface during curing in open-air.

This study developed and evaluated a series of ultraviolet (UV) curable self-matting waterborne polyurethane acrylate (UV-WPUA) coatings based on the self-wrinkled surface during UV-curing in the open-air. This method is simple, efficient, eco-friendly, and it does not require complicated or expensive equipment. The FT-IR spectrum indicates that the peaks of C[double bond, length as m-dash]C in UV-WPUA have disappeared after UV irradiation. The gloss value of the UV-WPUA cured film can be affected by the wrinkles on the surface of the film and adjusted it by controlling the content of the photoinitiator in the liquid coating, since the content influences the dimensions of the wrinkles. As the height of the wrinkle increased, the gloss value of the UV-WPUA cured film decreased, and when the incident angles are 20° and 60°, the gloss values are less than 3 GU and 5 GU, respectively. Moreover, the cured film has a maximum water contact angle of 109°, which is affected by wrinkles and positively correlated with the surface roughness of the film. Furthermore, the cured film has excellent properties of thermal stability, tensile strength, pencil hardness, cross-cut adhesion and resistance to abrasion properties, making it well suited for the furniture, leather, and textile applications.

Castor oil based high transparent UV cured silicone modified polyurethane acrylate coatings with outstanding tensile strength and good chemical resistance

Castor oil based high transparent silicone modified UV cured polyurethane acrylate coatings with outstanding tensile strength and good chemical resistance were developed with castor oil based polyurethane acrylates and thiol silicone resin. The UV cured coatings are with transparency in range of 90–98%, tensile strength as high as 10.2 MPa and elongation at break in the range of 88.4–162.5%. It is worth noting that the tensile strength of the coatings immersed in 3.5 wt% hydrochloric aqueous solution 144 h increased from 6.2 MPa to 15.5 MPa while the elongation at break is almost not changed, which reveals that the UV cured coatings also exhibit good chemical anti–corrosion performance. The UV cured coatings also show quite good UV resistance and adhesive properties.

Improving mechanical and water vapor barrier properties of the parylene C film by UV-curable polyurethane acrylate coating

Abstract Parylene C (PC) films have been widely used in many fields, such as metal anti-corrosion, electronic packaging, etc. However, the relatively poor mechanical properties and the deteriorated water barrier performance due to the easy fracture under external stress have restricted their application. It is a relatively simple and good method to maintain the water vapor barrier and enhance the mechanical properties of PC film by covering a flexible coating on its surface. In this work, a new polyurethane acrylate (PUA) coating was prepared and coated on the PC film by ultraviolet curing technology to form the PC/PUA composite film. The results showed that the PUA coatings could improve the water vapor barrier and mechanical properties of the PC film simultaneously. The water vapor transmittance rate was reduced from 1.1791 g·(m−2·day−1) of the original PC film to 0.5636 g·(m−2·day−1) of the PC/PUA composite film. The elongation at break and the impact energy were increased to 48.36% and 41.67%, respectively, which would widen the application of PC films in the fields of flexible electronics or smart wear.

UV cured silicon-containing polyurethane-acrylate coatings with non-traditional fluorescence and temperature-sensitive transparency

A kind of UV-curable silicon-containing hyperbranched polyurethane-acrylate coating was prepared and the features of UV curing reaction were investigated in detail. These UV cured coatings exhibit unexpected fluorescence emission under the excitation of UV and the fluorescence peaks of these UV cured products appear at about 320 nm with unimodal distributions. The UV cured coatings also exhibit unexpected temperature-sensitive transparency. The transmittance of these coatings is in the range of 85–98% at room temperature, however, the transmittance reduced significantly to be no more than 62% at 10 °C, especially, the transmittance of UV-HPSiPUA-HP3 is lower than 10%. The other performances such as pencil hardness, water contact angle, grade of adhesion and thermal stability of these coatings were also investigated. The UV cured silicon-containing polyurethane-acrylate coatings with non-traditional fluorescence and temperature-sensitive transparency have potential applications in chemical sensing, bio-imaging, anti-counterfeiting technology, temperature-sensitive optical sensors, etc.

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

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

Photo-crosslinked coatings from an acrylate terminated non-isocyanate polyurethane (NIPU) and reactive diluent

Non-isocyanate polyurethane acrylate coatings (NIPUAs) were prepared by photocrosslinking of mixtures of an acrylate terminated NIPU oligomers (A-Ol) and reactive (meth-)acrylate diluents. A-Ol were prepared by a transurethane polycondensation pathway followed by an acrylation reaction of the resulting hydroxy chain-ends. The influence of the reactive diluent content and chemical structures on the thermal and mechanical properties of these coatings has been investigated. The obtained materials exhibited thermal stabilities above 255 °C, Young modulus ranging from 2.6 to 9.2 MPa, tensile strength from 2.69 to 25.5 MPa and elongation at break from 56 to 470%.

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.

Comparative Study of Aromatic and Cycloaliphatic Isocyanate Effects on Physico-Chemical Properties of Bio-Based Polyurethane Acrylate Coatings.

Crude jatropha oil (JO) was modified to form jatropha oil-based polyol (JOL) via two steps in a chemical reaction known as epoxidation and hydroxylation. JOL was then reacted with isocyanates to produce JO-based polyurethane resin. In this study, two types of isocyanates, 2,4-toluene diisocyanate (2,4-TDI) and isophorone diisocyanate (IPDI) were introduced to produce JPUA-TDI and JPUA-IPDI respectively. 2,4-TDI is categorised as an aromatic isocyanate whilst IPDI is known as a cycloaliphatic isocyanate. Both JPUA-TDI and JPUA-IPDI were then end-capped by the acrylate functional group of 2-hydroxyethyl methacrylate (HEMA). The effects of that isocyanate structure were investigated for their physico, chemical and thermal properties. The changes of the functional groups during each synthesis step were monitored by FTIR analysis. The appearance of urethane peaks was observed at 1532 cm−1, 1718 cm−1 and 3369 cm−1 while acrylate peaks were detected at 815 cm−1 and 1663 cm−1 indicating that JPUA was successfully synthesised. It was found that the molar mass of JPUA-TDI was doubled compared to JPUA-IPDI. Each resin showed a similar degradation pattern analysed by thermal gravimetric analysis (TGA). For the mechanical properties, the JPUA-IPDI-based coating formulation exhibited a higher hardness value but poor adhesion compared to the JPUA-TDI-based coating formulation. Both types of jatropha-based polyurethane acrylate may potentially be used in an ultraviolet (UV) curing system specifically for clear coat surface applications to replace dependency on petroleum-based chemicals.

Fabrication and performance of UV cured transparent silicone modified polyurethane–acrylate coatings with high hardness, good thermal stability and adhesion

Conventional UV cured PUs suffer from low hardness, which will be scratched during the course of storage and transportation. They also undergoes severe pyrolysis when the temperature exceeds 200 °C, and the poor heat resistance limit their application in the high-temperature field. To address these challenges, a type of UV cured transparent coatings were prepared with thiol silicone resin and polyurethane-acrylate through thiol-ene click reaction. The coatings obtained are with high hardness, excellent scratch resistance, good thermal stability, fairly strong adhesion, efficient water resistance and good UV radiation resistance. More specifically, the pencil hardness and initial thermal decomposition temperature are in the range of 6 B–9 H and 297 °C–306 °C respectively, which are more superior to those of the conventional UV cured PUs. More strikingly, the coatings obtained with excellent scratch resistance because there are no traces on the coatings, even the slides are broken, when the cross cut tests were carried out on the coatings cured for 40 s–60 s. The coatings obtained are also with transmittance in the range of 85 %–99 %, adhesive properties to the slides can reach grade 0, water absorption in the range of 0.23 wt%–0.60 wt%, exposed to UV (7.8 mw.cm−2) at ambient for 180 min without turn yellow. The transparent silicone modified polyurethane–acrylate coatings prepared are promising for widespread applications in the information technology devices and automobile, etc.

Preparation of UV-Curable Low Surface Energy Polyurethane Acrylate/Fluorinated Siloxane Resin Hybrid Coating with Enhanced Surface and Abrasion Resistance Properties.

Low surface energy coatings have gained considerable attention due to their superior surface hydrophobic properties. However, their abrasion resistance and sustainability of surface hydrophobicity are still not very satisfactory and need to be improved. In this work, a series of utraviolet (UV)-curable fluorosiloxane copolymers were synthesized and used as reactive additives to prepare polyurethane acrylate coatings with low surface energy. The effect of the addition of the fluorinated graft copolymers on the mechanical durability and surface hydrophobicity of the UV-cured hybrid films during the friction-annealing treatment cycles was investigated. The results show that introducing fluorosiloxane additives can greatly enhance surface hydrophobicity of the hybrid film. With addition of 2 wt.% fluorosiloxane copolymers, the water contact angle (WCA) value of the hybrid film was almost tripled compared to that of the pristine PU film, increasing from 58° to 144°. The hybrid film also showed enhanced abrasion resistance and could withstand up to about 60 times of friction under a pressure of 20 kPa. The microstructure formed in the annealed film was found to contribute much to achieve better surface hydrophobicity. The polyurethane acrylate/fluorinated siloxane resin hybrid film prepared in this study exhibits excellent potential for applications in the low surface energy field.

Failure Behavior and Damage Mechanism of Acrylic Polyurethane Coating in Tropical Marine Atmospheric Environment

Failure Behavior and Damage Mechanism of Acrylic Polyurethane Coating in Tropical Marine Atmospheric Environment