Acrylic Polyol Research Articles

Curing process, mechanical property and thermal stability of acrylic polyurethane/Fe2O3 nanocomposite coatings

The effect of Fe2O3 nanoparticles (NPs) on the curing and properties of acrylic polyol HSU 1168 based coating were investigated. The SEM images showed that Fe2O3 NPs with the content £ 2 wt.% were dispersed regularly in the polymer matrix. The obtained results indicated that Fe2O3 NPs slowed down the curing process of acrylic polyol coating. Without nanoparticles, the neat HSU 1168 based coating has completely cured after 96 hours, whereas in the presence of 2 wt.% Fe2O3 NPs in coating matrix it needed 120 hours for a full curing. In addition, the relative hardness of nanocomposite coating has reduced with increasing the Fe2O3 NPs content. Without nanoparticles, the relative hardness of neat acrylic polyol coating was 0.88, whereas it was 0.75 when 4 wt.% Fe2O3 NPs was added into the coating matrix. Besides, incorporation of Fe2O3 NPs into the acrylic polyol coating also enhanced its abrasion resistance and impact resistance with 2 wt.% Fe2O3 NPs being the best content (i.e. 200 kG.cm of impact resistance and 408.8 L/mil of abrasion resistance). On the other hand, incorporation of Fe2O3 NPs into the coating matrix improved its thermal stability. The starting temperature for degradation of nanocomposite coating (with 2 wt.% Fe2O3 NPs) was 15 oC higher than that of the neat coating (without nanoparticles)

An antimicrobial acrylic polyurethane coating with TiO2-Ag hybrid nanoparticles

Abstract The purpose of this work is to fabricate the advanced organic antibacterial coating containing the strong photocatalytic nanomaterials. For this purpose, firstly the TiO2–Ag hybrid nanoparticles are synthesized by chemical reduction method. Then, the antibacterial coating based on acrylic polyol, polyisocyanate, and these TiO2–Ag hybrid nanoparticles has been prepared. Mechanical properties show that the optimal content of TiO2–Ag hybrid nanoparticles in the coating matrix is 2 wt%, with its abrasion resistance of 166.2 L/mil; impact strength of 195 kg cm; adhesion of size #1 and relative hardness of 0.78. In addition, FE-SEM analysis shows that the nanocomposite coating has a tight structure with homogeneous dispersion of TiO2–Ag nanoparticles in the polymer matrix. The paint film has good antibacterial activity and has great application prospects. Data from the antibacterial test indicates that in the presence of an acrylic polyurethane coating containing 2 wt% TiO2–Ag, the number of viable Escherichia coli decreased from 3.4 × 105 CFU/ml to 1.5 × 102 CFU/ml after 24 h of culture.

From theory to application: Innovative ice-phobic polyurethane coatings by studying material parameters, mechanical insights, and additives

This investigation introduces new insights into the influence of material parameters on the anti-icing properties of polyurethane (PU) coatings, encompassing chemical characteristics, cross-link densities, mechanical analysis, and additive diversity. To comprehensively address these aspects, a meticulous exploration was conducted to delve into the effects of these parameters on wettability and icephobicity. To fabricate the PU coatings, three distinct acrylic polyols with various hydroxyl content along with two widely employed aliphatic isocyanates boasting diverse %NCO values were utilized. By employing stoichiometric and non-stoichiometric ratios, an array of coatings with different crosslink densities and mechanical properties was fabricated. The principal influence of crosslink density alterations in PU coatings on ice nucleation temperature and ice adhesion strength emerged distinctly, underpinned by the establishment of hydrogen bonds between water molecules and polar functional groups within the coating, coupled with the appearance of a quasi-liquid layer (QLL). The mechanical properties, wettability characteristics, and surface roughness of the coatings were examined and it was clearly demonstrated that Young's modulus and physicochemical properties play significant roles in the characteristics of ice adhesion strength. In particular, lower Young's modulus in the samples was associated with reduced ice adhesion, albeit with compromised durability. In the next step of this investigation, the matrix demonstrating optimal mechanical properties and icephobicity was subjected to surface energy adjustment. This was accomplished by introducing various concentrations of both fluorinated and non-fluorinated additives. This adjustment led to a significant reduction of ice adhesion strength, measuring less than 100 Kpa as an icephobic PU coating. Nevertheless, it was observed that the effectiveness of the fluorinated additives diminished after repetitive icing-deicing cycles, while the non-fluorinated additive maintained its influence on ice adhesion strength even after numerous cycles. The interplay between material attributes, mechanical properties, and additive influences has been meticulously unraveled, charting a course for further advancements in the pursuit of robust icephobic coating.

Waterborne 2-component polyurethane coatings based on acrylic polyols with secondary alcohols

We report the effects of increasing the molecular weight of a secondary alcohol-based polyol in a two-component waterborne polyurethane (2 K-WB-PUR) formulation. The system consists of an acrylic polyol latex and a water-dispersible polyisocyanate (hmPIC, Basonat HW1000 from BASF). The polyols investigated incorporated hydroxypropyl methacrylate as a comonomer to introduce the secondary –OH groups, in contrast to typical polyols which have primary -OH groups. Three molecular weights of this polyol were prepared (Mn ≈ 5100, Ð = 2.4; 10,300, Ð = 2.7; or 12,900 g/mol, Ð = 3.6) with a uniform Tg (∼20 °C) and hydrodynamic diameter (dh) ≈ 120 nm. The polyol and polyisocyanate were mixed with a molar NCO:OH ratio of 1.3:1. The particle size of the mixed dispersion was monitored by dynamic light scattering. The 5 K sample remained stable in dispersion over 7 days whereas the higher molecular weight formulations flocculated after 1 day. Fourier Transform Infrared (FTIR) measurements revealed that all NCO groups were consumed within 15–23 h for all dispersed samples. Fluorescence resonance energy transfer (FRET) experiments were carried out on samples in the dispersed state as well as on films formed from these dispersions. Very little molecular level mixing was observed in the dispersed phase for the samples. In the films, a large extent of mixing was observed in the 5 K sample whereas the extents of mixing for the higher molecular weight samples were reduced. The FTIR measurements recorded as the films formed showed that the NCO consumption in the 5 K film (t1/2 = 56 h) was comparable to an analogous 2 K-WB-PUR formulation based on a 5 K primary alcohol from a previous study. Surprisingly, the NCO consumption in the higher molecular weight samples was faster (t1/2 = 31, 32 h). We found that the composition of the resulting films formed from higher molecular weight polyols contained a greater relative ratio of polyurea to polyurethane.

Stratification of polyisocyanate in two-component waterborne polyurethane films

The coatings industry continually seeks advancements in waterborne two-component polyurethane (2 K WBPU) systems, given their potential for environmentally friendly applications and superior film properties. This study explores the mechanistic aspects of film formation in 2 K WBPU coatings formulated with an acrylic polyol and a polyisocyanate (PIC) derived from a trimer of hexamethylene diisocyanate (HDI-trimer). To enhance water dispersibility—a key parameter in industrial applications—the HDI-trimer is modified with a short polyethylene glycol, producing a hydrophilically modified PIC (hmPIC). While prior studies identified hmPIC as an effective reactive plasticizer for the polyol, the common practice of adding unmodified HDI-trimer (uPIC) to hmPIC for moisture sensitivity reduction necessitates a deeper understanding of film properties. Using fluorescence resonance energy transfer (FRET) and confocal fluorescence microscopy, we investigated the effects of blending uPIC with hmPIC on coalescence, phase separation, and film stratification in 2 K WBPU systems. Notably, environmental factors like relative humidity were found to influence film stratification significantly. This finding has critical implications for coating performance, such as durability and water resistance. A novel method was also introduced to monitor water permeation within stratified films, offering a valuable tool for optimizing film properties in real-world applications. This study underscores the importance of strategic component interactions in polymer coatings, suggesting that controlled film stratification can significantly enhance film performance in industrial settings.

Development of protective coating system using natural rubber – acrylic polyol resin for mild steel

Purpose The purpose of this study is to develop a protective coating system on mild steel panel incorporating epoxidized natural rubber with acrylic polyol resin. Design/methodology/approach In this work, a novel attempt is made to develop binder coatings using epoxidized natural rubber-based material and an organic resin (acrylic resin) for corrosion protection on metal substrate. Seven different samples of multifunctional coatings are developed by varying the compositions of epoxidized natural rubber (ENR) and acrylic resin. The properties of the developed coatings have been characterized using analytical methods such as Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). EIS has been carried out for 30 days to evaluate the corrosion resistance after immersing into 3.5 wt.% of sodium chloride. Cross hatch cut tester (CHT) has been used to study the adhesive properties. UV–Visible Spectroscopy (UV–Vis) was also used to assess changes in the coating-film transparency of the natural rubber-based coating systems in this study. Findings The developed coatings have formed uniform layer on the substrate. CHT results show excellent adhesion of the coatings. Higher concentrations of ENR have higher transparency level, which reduces when the acrylic concentration increases. FTIR analysis confirms the crosslinking that occurred between the components of the coatings. Based on the impedance data from EIS, the incorporation of natural rubber can be an additive for the corrosion protection, which has the coating resistance values well above 108Ω even after 30 days of immersion. Practical implications The blending method provides a simple and practical solution to improve the strength and adhesion properties of acrylic polyol resin with epoxidized natural rubber. There is still improvement needed for long-term applications. Originality/value The work has been conducted in our laboratory. The combination of natural rubber-based materials and organic resins is a new approach in coating research.

New insights into tailoring physicochemical properties for optimizing the anti‐icing behavior of polyurethane coatings

AbstractThe most popular topcoat in the coatings industry, polyurethane (PU), still lacks an understanding of ice‐related phenomena and hence achieving an icephobic PU‐based coating has remained an important unresolved issue. This work presents fresh perspectives on how factors including chemical characteristics, cross‐link density, and mechanical characterization impact the anti‐icing capabilities and ice‐adhesion of PU coatings. In this regard, the effects of the of aforementioned coatings having various crosslink densities on wettability, ice formation, and ice adhesion were assessed via multiple approaches. Two acrylic polyols with different hydroxyl content and two commonly used aliphatic polyisocyanates with different %NCOs were utilized to fabricate the PU coatings. In addition, coatings were designed with different stoichiometric ratios providing a route to various crosslink densities and mechanical properties. Wettability characteristics were investigated using water contact angle, contact angle hysteresis, and sliding angle. The roles of urethane linkages and hydrogen‐bond formation between water molecules and urethane composition of PU coatings on ice nucleation and ice adhesion were studied through DSC, push‐off, and centrifugal tests. Mechanical characteristics and surface roughness of the coatings were investigated by tensile test and optical profilometer, respectively.

Waterborne polyurethane via encapsulated blocked isocyanate crosslinker for 1 K clearcoats

Herein, a waterborne polyurethane clearcoat with excellent chemical and physical performance through an encapsulation system has been developed. The encapsulation system in this study incorporated blocked polyisocyanate (b-PIC) as a crosslinker with an acrylic polyol to ensure homogeneous dispersion under water-based conditions. An acrylic polyol was designed to readily disperse into the water phase, fulfill the requirements of a clearcoat, and effectively encapsulate b-PIC. The structure of the core-shell encapsulation system enabled both homogeneous dispersion and close proximity between the acrylic polyol and b-PIC, resulting in a uniform crosslinking clearcoat. Three different clearcoats were prepared: two water-based b-PIC systems with both polyisocyanate encapsulated dispersion (PED) and conventional b-PIC dispersion (CPD) without encapsulation, and a solvent-based (SB) b-PIC dispersion with ethyl cellosolve. Their crosslinking and mechanical properties were characterized. Using dynamic light scattering (DLS), it was confirmed that PED contained synthesized encapsulated particles smaller than 80 nm with a narrow particle size distribution. The cured PED-containing clearcoat exhibited a higher gloss of 73.6 at 20° compared to that of CPD. In addition, the surface mechanical properties of cured PED waterborne clearcoat using pencil hardness, nano-indentation (NI), and micro-scratch testing (MST) were measured. In particular, the PED clearcoat exhibited superb resistance to water penetration, maintaining more than 95 % transmittance using a UV–Vis spectrometer. Finally, the glass transition temperature of PED, CPD, and SB clearcoats was confirmed by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). These indicated that the PED clearcoat system could be utilized in waterborne coatings technology as a useful and inexpensive technology that addresses the need to reduce volatile organic compound (VOC) production for improved environmental protection.

Extending the pot life of polyurethane coatings using organic diones

PurposeThis study aims to extend the pot life without altering the qualities and performance of the coating, which is important to increase when manufacturing polyurethane coatings.Design/methodology/approachAn acrylic polyol from a mixture of different monomers of hydroxypropyl methacrylate, methacrylic acid, 2-ethylhexyl acrylate, methyl methacrylate and n-butyl methacrylate was prepared with different ratios of 2,4-pentanedione as a pot life extender. The reaction takes place in presence of di-tert-butyl peroxide as initiator with samples (T1–T7). The physical properties of prepared acrylic polyol were characterized. Then, coating polyurethane varnish was prepared from the prepared acrylic polyol with an aliphatic polyisocyanate in a 1:1 equivalent ratio of OH:NCO at room temperature, in presence of paint thinner (diluents/solvent) and dibutyltin dilaurate as a catalyst to give samples (T1C–T7C). This coating was evaluated via Fourier-transform infrared spectroscopy, drying time, hardness and gloss, distinctness of image and reflected image quality.FindingsThe coating has a prolonged pot life while still maintaining the other qualities, thanks to the greater 2,4-pentanedione content.Originality/valueIt is desired to have a paint which has a satisfactory pot life, short curing time and reduces many drawbacks such as inefficient working and deterioration of the paint before application.

Preparation and Properties of Autocatalytic Biobased Waterborne Polyol from Rosin Based Epoxy Resin

Due to the complex heterogeneous film forming process of two-component waterborne polyurethane (2K-WPU), the crosslinking reaction rate of 2K-WPU cannot meet the demand of efficient application in coatings. In order to improve the crosslinking reaction rate of 2K-WPU, a waterborne polyol containing tertiary amine groups was synthesized from rosin based epoxy resin and secondary amine compound, and then autocatalytic 2K-WPU was prepared by crosslinking the rosin based waterborne amino polyol with polyisocyanate. The structure of the polyol from rosin based epoxy resin was characterized with Fourier infrared (FT-IR) and nuclear magnetic resonance (NMR). The crosslinking kinetics and the crosslinked product of the rosin based waterborne amino polyol were also compared with a commercial acrylic polyol. It was shown from the results that the crosslinking reaction rate of the rosin based waterborne amino polyol was faster than that of the commercial acrylic polyol, which indicated the tertiary amine groups chemically bonded in the rosin based polyols could autocatalyze the crosslinking reaction of 2K-WPUs with catalysts free. The film of the rosin based waterborne amino polyol had excellent impact strength, adhesion, flexibility, hardness, gloss, fullness and solvent resistance, showing a good application prospect in the field of waterborne coatings.

Enhanced mar/scratch resistance in automotive clear coatings by modifying crosslinked polyurethane network with branched flexible oligomers

Mar and scratch resistance are a major concern for automotive and other industrial sectors from causing inconvenient aesthetic changes on clear coats. Then, a series of two-component solvent-borne polyurethane coatings were formulated with branched polycaprolactone (PCL) oligomers. The effect of the partial substitution of acrylic polyols by tri- and tetra-functional PCL polyols on adhesion, chemical resistance, thermo-mechanical properties and aesthetic response was analysed. The PCL polyols drove to plasticised networks with lower glass transition temperature (Tg) and promoted rubbery state at room temperature. The associated growth in chain mobility did not appreciably affect the key performance of the coatings, apart from the chemical resistance of formulations with PCL triols. Furthermore, remarkable improvement of wear resistance from promoted recovery response was demonstrated. The clear coats with moderated content of PCL polyols yielded a reduced loss of specular gloss with time after repeated scrubbing operations by an abrasive paper. The proposed approach, thus, is presented as a versatile strategy to tailor the mechanical surface properties of clear coats.

Monitoring the reaction kinetics of waterborne 2‐pack polyurethane coatings in the dispersion and during film formation

AbstractWe examine the nature of the chemical reactions taking place in a waterborne two‐component polyurethane formulation consisting of an acrylic polyol latex and a hydrophilically modified polyisocyanate (hmPIC) based on the trimer of hexamethylene diisocyanate. The hmPIC was diluted with 30 wt.% of an organic solvent to reduce its viscosity and formed small (~20 nm) droplets when dispersed in water. In mixtures of the polyol and hmPIC, we monitored the rate of NCO group disappearance in the dispersed state by FTIR and showed that it varied with the choice of organic solvent. We developed a method based upon 19F NMR to distinguish the reaction of the NCO groups with OH groups from the polyol from its reaction with water. FTIR measurements on films formed from these dispersions showed how the disappearance of NCO groups depended on relative humidity. In a more semi‐quantitative way, these measurements indicated the relative extent of urethane versus urea formation in these model coatings.

Film Formation of Waterborne 2K Polyurethanes: Effect of Polyols Containing Different Carboxylic Acid Content

While the interaction of NCO with carboxylic acids has been documented, a comprehensive knowledge of its effect on the film formation in a two-component waterborne polyurethane (2K-WPU) system is lacking. In this work, we synthesized a series of carboxyl-functional acrylic polyols (Mn ≈ 5000 g/mol, Đ ≈ 2.7, Tg ≈ 15 °C) of uniform diameter (120 nm) with varying amounts of methacrylic acid introduced into the latex. For 2K-WPU dispersions with a molar NCO/OH ratio of 1.3:1, we monitored particle size by dynamic light scattering and NCO consumption by FTIR. In the dispersion, we found that the particle size remained nearly constant, and the NCO was almost completely consumed after 2 days. Incorporating COOH in the polyol latex accelerated the consumption of NCO. We synthesized polyol samples labeled with donor and acceptor dyes for fluorescence resonance energy transfer (FRET) studies of polymer diffusion and molecular mixing. In films formed from the polyol latex in the absence of hmPIC, the COOH content of the polyols had no significant effect on the rate or extent of polymer diffusion. In contrast, in films formed from the 2K-WPU dispersions with a stoichiometric NCO/OH ratio (1.3:1), the extent of ET rapidly increased to the maximum value, showing that the full extent of molecular mixing of the two components can be accomplished in films. Thus, the hmPIC acts as a reactive plasticizer. In parallel experiments in which the hmPIC was labeled with the donor dye, we found evidence for partial mixing of the PIC and polyol in the dispersed state. We also showed that the rate of mixing of the hmPIC and the polyol in the films cast from these dispersions was accelerated by −COOH groups in the polyol.

Acrylic‐ester‐polyol based novel two‐component polyurethane clear coat: Evaluation of performance characteristics

AbstractIn the current study, a combination of acrylic polyol (AP) and ester polyol (EP) were synthesized and reacted at variable ratios with hexamethylene diisocyanates and isophorone diisocyanates to prepare a transparent two‐component polyurethane (PU) coating formulation. The formations of the polyol system, isocyanate system, and the PU systems were confirmed by 1H nuclear magnetic resonance and Fourier‐transform infrared spectroscopy. Transparency of the coatings was examined using haze, and gloss measurement, which showed acrylic‐ester‐polyurethane (aePU‐5 and aePU‐6) have 91.5% and 91.8% transparency and gloss of 90.3 and 90.7 GU respectively. The thermal properties like Tg and the thermal stability of the coatings were verified using differential scanning calorimetry, and thermogravimetric analysis respectively which was found to increase with increasing EP content and decreasing AP content which may be ascribed to improved compatibility of copolymers, and homogeneity in PU along with enhanced crosslinking density. The degree of adhesion of coating with the substrate was validated from lap‐shear, and cross‐cut tape test which showed improved performance at AP:EP ratio of 60:40. The coatings were found to exhibit resistance toward pencil hardness with aePU‐5 and aePU‐6 having the optimum resistance of 9H. The surface morphology and topography were observed under scanning electron microscopy, and atomic force microscopy, respectively. The outcome confirms the higher smoothness of the surfaces subjected to the increase in EP content. The PU system with 40 wt% AP content and 60 wt% EP designated as aePU‐5 was found to exhibit optimum performance.

Polyurethane coatings cured via azide-alkyne cycloaddition using reduced-viscosity poly(alkynyl carbamate) prepolymers

Alternative crosslinking polyurethanes (ACPUs) were created by reacting a commercial allophanate-modified polyisocyanate with propargyl alcohol to yield a poly(alkynyl carbamate); a polyazide co-reactant was created from an acrylic polyol. Conversion of the polyisocyanate into the corresponding poly(propargyl carbamate) resulted in a dramatic viscosity increase. Poly(alkynyl carbamate) prepolymers with lower viscosities were designed by replacing various fractions of the propargyl alcohol with commercial glycol ether plasticizers, ethylene glycol monoethyl ether (EGMEE), diethylene glycol monomethyl ether (DEGMEE), and diethyleneglycol monobutyl ether (DEGBE). Triethylene glycol monopropargyl ether was also studied to provide plasticization with no sacrifice of alkyne functionality. For each commercial glycol ether plasticizer, viscosity was unaffected or increased at a loading level of 10 mol%. At 25 mol%, average viscosity reduction was 36 %, with DEGBE yielding the greatest reduction at 55 %. At 33 mol%, no further decreases were observed. Triethylene glycol monopropargyl ether yielded a 76 % reduction in viscosity at 33 mol%; 100 mol% substitution yielded no further reduction. Coatings produced from the modified poly(alkynyl carbamate)s were softer and displayed lower glass transition temperatures compared to a polyisocyanate/polyol control and a 100 % propargylated poly(alkynyl carbamate)/polyazide control. Solvent resistance of the modified coatings was the same as the controls except for those created from DEGBE and from DEGMEE at 33 mol%.

Monitoring Polymer Diffusion in a Waterborne 2K Polyurethane Formulation Based on an Acrylic Polyol Latex

We report experiments based upon fluorescence resonance energy transfer (FRET) measurements designed to examine mixing at the molecular level of the components of a waterborne 2K polyurethane (WB2KPU) formulation. The system consists of an acrylic polyol latex (Mₙ = 4200 g/mol, D = 2, Tg ≈ 15 °C) with a uniform hydrodynamic diameter (dₕ) ≈ 120 nm plus a water-dispersible polyisocyanate (hmPIC, Basonat HW1000 from BASF). We prepared components labeled with phenanthrene (Phen) as the donor dye or with a dimethylaminobenzophenone (Nben) as the acceptor dye. Dynamic light scattering was used to monitor the size and size distribution of the components in the dispersed phase in solution. This signal was dominated by the polyol nanoparticles, which were much larger than the tiny droplets formed by the hmPIC in water. Experiments were carried out at a mole ratio of NCO/polyol-OH of 1.3. We found that the particle size and narrow size distribution remained unchanged up to 22 h after mixing the polyol with the PIC. FRET experiments were carried out on samples in the dispersed state as well as on films formed from these dispersions. Films formed from a 1:1 mixture of (polyol-Phen + polyol-Nben) showed relatively little energy transfer (ΦET = 0.19) even after several hours aging at ambient temperature, indicating that little polymer diffusion occurred in these low-molecular-weight latex films. In contrast, films formed from mixtures of (polyol-Phen + polyol-Nben + hmPIC) showed more extensive energy transfer (ET) (ΦET = 0.51), indicating essentially complete mixing at the molecular level of the polymer molecules in the presence of hmPIC. The key conclusion is that hmPIC is a reactive plasticizer that promotes diffusion in this system on a much faster scale than the cross-linking reaction. This result is confirmed by experiments that examined mixtures of (hmPIC-Phen + polyol-Nben), which also showed essentially molecular scale mixing between these two different components. In this later system, aging at room temperature led to a small decrease in ΦET over time that was more prominent for films aged at high humidity (75%) than at lower humidity (45%). This result suggests that hydrolysis of NCO groups in the film, leading to polyurea formation, promotes local phase separation accompanied by a net increase in the average separation of Phen and Nben groups in the film.

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.

Synthesis and characterization of solvent free acrylic copolymer for polyurethane coatings

Solvents play a huge role in the manufacturing of various acrylic resins due to their ability to control the molecular weight, reduce the viscosity and enhance the flow and levelling of the coatings. However, they contribute significantly to volatile organic content (VOC) which is a key parameter in the field of coatings industry. In view to minimise VOC, various polyols have been studied as reactive diluents/solvents to replace conventional solvents in acrylic polyol synthesis. In this manuscript, 1,3-propanediol oligomer, a 100 % bio-based oligomer has been used to completely replace the conventional solvent in the acrylic polyol synthesis. 1,3-propanediol not only acts as a solvent but also takes part in the curing process by reacting with polyurethane (PU) cross-linkers. To achieve the same properties as solvent based acrylic polyol resins, suitable monomers, initiators and reaction conditions were explored. Most of our designs exhibited viscosity in the range of Z6 to Z8 on Gardener scale at 25 °C. A solitary design resulted in a viscosity of Z4-Z5, which was well within our required parameters. This acrylic polyol resin based on 1,3-propanediol was cross-linked with PU cross-linkers in clear coat. The obtained film was then studied using various analytical techniques such as dynamic mechanical analyser (DMA), thermogravimetric analysis (TGA), gel permeation chromatography (GPC) and fourier transform infrared (FTIR) spectroscopy. The advantage with 1,3-propanediol based solvent free acrylic polyol resin is the reduction of VOC from 400 g/L to ∼ 160 g/L. It is observed that the coatings obtained from this acrylic polyol resin exhibited comparable performance in two component (2 K) PU coatings to that of in-house solvent borne acrylic systems having high VOCs.

Investigation of crosslinking, mechanical properties and weathering stability of acrylic polyurethane coating reinforced by SiO2 nanoparticles issued from rice husk ash

In this study, rice husk ask (RHA)-SiO2 nanoparticles were successfully synthesized from rice husk ash by precipitation method. TEM images indicate that as-synthesized nanoparticles had amorphous structure with a relatively homogeneous size of about 20 nm. Crosslinking process, mechanical properties and weathering degradation of the nanocomposite coating based on acrylic polyols and polyisocyanate in the presence of nano RHA-SiO2 were investigated. The mechanical properties of the coating show the highest values with 2.5 wt%. of nano RHA-SiO2 as filler. FE-SEM analysis demonstrates that nano RHA-SiO2 nanoparticles were well dispersed in the coating. IR analysis, relative hardness, gel fraction and swelling degree measurements show that the nanoparticles improved conversion performance of isocyanate groups, gel fraction, swelling degree and relative hardness of the coating. Accelerated weathering test indicates that, after 36 cycles of test, the nanocomposite coating was degraded with the formation of several holes on the coating surface and the recorded weight loss was 9.1%. For the neat coating, the formation of various large holes of dimension ranging from 20 nm to several μm on the surface was observed and the weight loss is measured to be higher (12.7%) in the same conditions. Nano RHA-SiO2 possibly play a dual role: i) UV protector and ii) nanofiller helping to prevent the invasion of aging agents.

Colour analysis of organic synthetic dye coating paint films consisting 4-hydroxycoumarin derivatives after exposed to UV-A

This work investigates the visible optical stability of coating paint film consisting organic synthetic dye, 4-hydroxycoumarin derivatives to the exposure to ultraviolet A (UV-A) light. An azo dye was synthesized by coupling diazonium salt of aniline derivative (obtained by diazonation of 4-chloroaniline in presence of sodium nitrite and hydrochloric acid) with 4-hydroxycoumarin in the presence of sodium hydroxide. The azo dye was mixed with xylene before using it as a pigment in the coating composition. The mixture of poly(methyl methacrylate) (PMMA) and acrylic polyol was used as the coating binder. The synthesized dye and binder were then mixed at specific ratio to form a complete coating solution. Two coating solutions with PMMA having different molecular weights (Mw: 350,000 gmol−1 and Mw: 996,000 gmol−1) were used in this study. Each of them was labelled as 350 K and 996 K indicating its molecular weight. Both mixtures were applied as coating paint films on glass substrates were exposed to UV-A for fast photo-degradation process. The visible optical stability of the coating paint films was measured and recorded at an interval of eight-hours exposure for 35 days using the Commission Internationale de l’Eclairage (CIE) L*a*b* colour coordinate system. The obtained datas were analysed using standard deviation (STD). In this study, both coating samples showed low standard deviation for hue angle, namely 0.206 for 996 K and 0.258 for 350 K which indicates a high colour stability. However, the 350 K possesses a smaller colour difference (ΔE) of 0.798 compared to 1.418 for 996 K.