Two-component Waterborne Polyurethane Research Articles

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.

Preparation and application of fluorine-containing acrylate emulsion in two-component waterborne polyurethane coatings

Preparation and application of fluorine-containing acrylate emulsion in two-component waterborne polyurethane coatings

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.

Antistatic and antibacterial two-component waterborne polyurethane coating

Antistatic and antibacterial two-component waterborne polyurethane coating

Effect of Coating Process on Properties of Two-Component Waterborne Polyurethane Coatings for Wood

Acrylic acid has good environmental weather resistance, water resistance, alcohol resistance, dirt resistance, and other properties. An acrylic acid dispersion with a core–shell structure was prepared and reacted with a polyisocyanate-type curing agent to prepare a waterborne polyurethane topcoat suitable for wood. The prepared two-component polyurethane topcoat was used in combination with a waterborne primer and a waterborne sealing primer and applied to Pine (Pinus strobus) boards to carry out gloss, wear resistance, and adhesion experiments. The effects of different coating amounts and spraying times on the comprehensive properties of the wood coatings were studied. The experimental results showed that when the self-made two-component polyurethane topcoat for wood was matched with the primer and the sealing primer, the coating amount of the sealing primer had little effect on improving the adhesion and wear resistance but had a significant effect on the gloss. The spraying times of the primer and the topcoat greatly impacted the adhesion, but they had no decisive impact on the improvement of the gloss. When the coating amount was 60 g/m2 for the waterborne sealing primer, 100 g/m2 for waterborne primer, and 120 g/m2 for the self-made topcoat and the coating was sprayed twice, the comprehensive performance of the obtained film on the wood was the best. This research on the preparation and coating process optimization of the two-component waterborne polyurethane coatings for wood can provide a technical basis for the application of two-component waterborne polyurethane topcoats for wood.

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.

Preparation of PVA/PU/PUA microcapsules and application in self-healing two-component waterborne polyurethane coatings

Preparation of PVA/PU/PUA microcapsules and application in self-healing two-component waterborne polyurethane 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.

Two-component waterborne polyurethane modified with terpene derivative-based polysiloxane for coatings via a thiol-ene click reaction

Waterborne polyurethane has gradually become a focus among researchers due to its low volatile organic emissions and low pollution. However, some problems exist with waterborne polyurethane, such as poor mechanical properties, obvious hydrophilicity and poor heat resistance. Herein, a terpene-modified polysiloxane-based polyurethane was designed to solve the abovementioned problems. 3-Mercaptopropylmethyldimethoxysilane and octamethylcyclotetrasiloxane were used as raw materials to prepare hydroxyl-terminated polysiloxane (PMMS). As a derivative of camphene, biomass resources, isobornyl acrylate was grafted to the prepared polysiloxane side chain through the thiol-ene click reaction under ultraviolet light irradiation conditions. Terpene-based polysiloxane (PMMS-I) was used as one of the polyol components to modify two-component waterborne polyurethane. Due to the combination of low surface energy polysiloxane and a hydrophobic terpene derivative, the hydrophobicity of the modified waterborne polyurethane was significantly improved, where the static water contact angle was increased from 70.7 ° to 101.2 ° and the water absorption was reduced from 16.0% to 6.9%. In addition, because of the unique rigidity of the terpene ring, the tensile strength of the modified polyurethane was significantly improved from 4.70 MPa to 8.82 MPa. In addition, the thermogravimetric analysis results showed that the thermal stability of the modified polyurethane was ameliorated. In terms of improving the properties of polymer materials, terpene bio-based compounds have broad potential.

Terpene derivative-containing silicone two-component waterborne polyurethane for coatings

With increasing desires to protect the environment, volatile organic solvent emissions have been restricted, and there is a trend in developing waterborne polyurethanes. However, poor water resistance and low mechanical strength of waterborne polyurethane are major obstacles. Herein, we propose a terpene-modified polysiloxane-based polyurethane that solves the above-stated problems. In the presence of the Karstedt catalyst, isobornyl acrylate (IBOA) was introduced into the branch of hydrogen-containing silicone oil (HSO) through the hydrosilylation reaction. Then, it was mixed with an alkaline aqueous solution to convert the remaining SiH bonds to Si−OH bonds, which can be used as a polyol component (IBOA-Si-OH). Then, the mixtures of IBOA-Si-OH and polypropylene glycol-400 (PPG-400) were used as polyol components to react with polyisocyanate-3100 (PI-3100) in preparing a two-component waterborne polyurethane. Compared with the unmodified polyurethane film, the contact angle of the polyurethane film modified with IBOA-Si-OH was greater than 102°, which increased by 28°. The water absorption test showed that the modified polyurethane membrane nearly doubled its ability to prevent water penetration (from 18.11 % to 9.38 %). Although the introduction of silicone improved the water resistance of waterborne polyurethane, the mechanical properties were reduced. The introduction of IBOA into the silicone side chain improved the mechanical properties of polyurethane. Comparing WPU-Si with WPU-2, the tensile strength improved by 85.56 % (from 3.47 MPa to 6.44 MPa). Thermogravimetric analysis and dynamic thermomechanical analysis indicated that silicone reduced Tg and thermal stability, but participation of IBOA made up for this deficiency. Terpene biobased compounds have great potential and application prospects in the modification of polymer materials.

The optical shielding performances and mechanisms of green flame-retardant two-component matte films under various application conditions.

Herein, we meticulously investigated the optical shielding performances and mechanisms of green flame-retardant two-component waterborne polyurethane matte films based on a previous study. The relevant performances were evaluated by changing various environmental factors including nanoparticle content, pH, temperature and storage-time. Specifically, upon combination with TiO2, the ultraviolet-light transmittance was reduced to 1.9% and the 60° glossiness decreased by 63%. When the pH was 8.0, the shielding efficiency and transmittance of ultraviolet light were 100% and 0%, respectively. The 60° glossiness of spin-films increased with an increase in storage time. Besides, TiO2 nanoparticles were beneficial for delaying the thermal decomposition via synergistic flame retardance.

A green approach to preparing hydrophobic, electrically conductive textiles based on waterborne polyurethane for electromagnetic interference shielding with low reflectivity

A green method was employed to fabricate a coated textile with hydrophobic surface that provided electromagnetic interference shielding performance with low reflectivity. First, two-component waterborne polyurethane dispersions modified with hydroxyl-terminated polydimethylsiloxane were synthesized. Multi-walled carbon nanotubes (CNT) and graphene were well dispersed in water via high pressure microfluidizer. Waterborne polyurethane and fillers containing 80% CNT and 20% graphene were applied to textiles by dipping method. The water contact angles of the polyurethane coating and the coated textile were 103.4° and 153.6°, respectively, when the polyurethane contained 10% hydroxyl-terminated polydimethylsiloxane. The electromagnetic interference (EMI) shielding effectiveness (EMI SE) of the coated textile (3% filler loading) could achieve 35 dB with a thickness of only 0.35 mm and the reflectivity is ca. 41.4%. By dipping a textile into polyurethane dispersions with different filler loadings (1% and 3%) to obtain a coated textile with a two-layer structure coating. EMI SE of the coated textile reached 30 dB and the reflectivity was only ca. 26.5%, indicating 26.5% of the electromagnetic waves is reflected during the propagation process when 99.9% electromagnetic waves is attenuated. Possible attenuation mechanisms of electromagnetic waves such as dielectric loss, multiple reflections, scattering and conductive loss were discussed. The mechanical properties, thermal conductivity and thermal stability of the coatings and coated textiles were studied. The coated textiles fabricated in a green and facile approach with excellent electromagnetic shielding performance and low reflectivity have great potential in advanced EMI shielding applications.

Self-Assembly of Amphiphilic Linear-Dendritic Carbosilane Block Surfactant for Waterborne Polyurethane Coating.

The traditional two-component waterborne polyurethane coating system cannot effectively inhibit the undesirable side reaction between polyisocyanate and water during curing hardening. It is difficult to avoid the microbubbles formed by this reaction during the film formation process, which severely degrades the appearance and decreases the performance of the film. Therefore, the addition of an amphiphilic Linear-Dendritic carbosilane Block Surfactant (LDBS) to the hardener can physically separate the polyisocyanate emulsion from water through self-assembly. The bubble-free film thickness (BFFT) of the two-component waterborne polyurethane coating in this study is approximately 1.5-fold greater than commercial waterborne polyurethane coatings in today’s coating industry. Fourier transform infrared spectroscopy (FT-IR) varied the effectiveness of LDBS for inhibition of the undesirable side reaction. The successful application of the waterborne polyurethane coating with LDBS on the 600 km/h high-speed maglev train provides a technical solution for large-scale industrialization of waterborne polyurethane coating and complete replacement of solvent polyurethane coating.

Study of the Effect of PGDA Solvent on Film Formation and Curing Process of Two-Component Waterborne Polyurethane Coatings by FTIR Tracking

Waterborne polyurethane coatings were prepared using polyhydroxyacrylate dispersion, polyisocyanate, and propylene glycol diacetate (PGDA). The rate of reaction between hydroxyl and NCO groups in film formation and curing processes was studied by FTIR. The influence of PGDA amount on film formation and curing was also studied. Results showed that PGDA content had a significant effect on the curing process. With less than 10% PGDA, the role of PGDA was more to assist diffusion of polyhydroxyacrylate and polyisocyanate resin droplets. This promoted the reaction between hydroxyl groups and NCO. With more than 10% PGDA, its effect as a solvent was more and it inhibited the reaction between hydroxyl and NCO groups. When the amount of PGDA was about 10%, the synergy between both the roles promoted the crosslinking and curing reactions. The extent of the curing reaction of NCO was more than 70% in 4 h, which was significantly higher, compared with that of about 30% without PGDA. The good applicability and appearance of the waterborne polyurethane coating prepared in this study were verified for the application to carbon fiber metro vehicles.

Self-Catalytic Two-Component Waterborne Polyurethanes with Amino Polyols from Biomass Based Epoxy Resin

In order to improve the crosslinking reaction rate of two-component waterborne polyurethanes (2K-WPUs) in the absence of ungreen external catalysts, waterborne polyols containing different tertiary amines in molecular structure were synthesized from a turpentine-based epoxy resin (TME) and secondary amines (N-benzylethanolamine and diethanolamine). Then self-catalytic 2K-WPUs were prepared with the waterborne amino polyols and a hydrophilically modified hexamethylene diisocyanate tripolymer. The structure and micromorphology of TME based polyols were identified using nuclear magnetic resonance (1H NMR, 13C NMR), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy techniques. The crosslinking reaction of 2K-WPUs was monitored using differential scanning calorimetry (DSC) and FT-IR methods. Kinetics analysis from DSC showed the activation energy of the crosslinking reaction of 2K-WPUs reduced obviously by using amino polyols, which indicated the tertiary amines chemically bonded in the polyols could self-catalyze the crosslinking reaction of 2K-WPUs without adding small molecular toxic catalysts. Small steric hindrance of the tertiary amines led to high catalytic activity. The properties of the crosslinked products of the waterborne TME based polyols were investigated by DSC, thermogravmetric analysis and dynamic mechanical analysis (DMA). The results showed high hydroxyl value of the polyol and aromatic ring in the polyol structure resulted in high storage modulus (G′) and glass transition temperature (Tg) of the crosslinked products. More C–N bond content of the crosslinked products of the waterborne amino polyols decreased the thermal stability in the first degradation stage of the products.

Preparation and Performance Optimization of Two-Component Waterborne Polyurethane Locomotive Coating

This paper reports the effects of different formulas on the performance of waterborne polyurethane (WPU), including two-component WPU and curing agent, wetting dispersant, defoaming agent, and wetting agent. The optimization of rheological additives selection, through the optimization of coating physical properties and chemical properties, can make the film show uniform color and appearance without pinholes, bubbles, or wrinkles, and have a long probation period. Through the analysis of performance after a 1000-h quick ultraviolet (QUV) aging test, the light reduction rate is 23.19%, and the color difference is 1.9. As can be seen from the scanning electron microscope (SEM) image and the three-dimensional stereomicroscope, the film shows relatively uniform dispersion, good compactness, and smooth surface. The two-component WPU topcoat is found to have high gloss 87.1 (60°) and high weather resistance, which provides a positive indication for the modulation and production of waterborne locomotive paint.

Synthesis and properties of water-dispersible polyisocyanates carrying sulfonate

A series of N-alkylated aminosulfonic acids (NASAs) were synthesized with 1,4-butane sultone and primary amines and then reacted with hexamethylene diisocyanate trimer to obtain water-dispersible polyisocyanates (WDPs). Two-component waterborne polyurethane (2K-WPU) coatings were finally prepared by the reaction of WDPs and aqueous hydroxyl resins. The structures and properties of WDPs and 2K-WPU coatings were characterized. The effects of the categories and amounts of NASAs on the properties of WDPs and 2K-WPU coatings, including viscosities, water resistance and transparency, were investigated. The results showed that the average molecular weights and viscosities of the WDPs increased with the increase in the amounts and molecular weights of NASAs. 3-(Cyclohexylamino)-1-propanesulfonic acid possesses a high molecular weight, resulting in low-concentration –SO3 per mass, so a high concentration up to 3.5 wt% was needed to meet water-dispersible requirements. On the other hand, 3-isobutylamino-1-propanesulfonic acid (IBAPS) has high-concentration –SO3 per mass and only a low concentration (2.5 wt%) was required to offer satisfactory water dispersibility. 2K-WPU film cured by IBAPS-WDP displayed high gloss, good transparency and excellent water resistance owing to suitable steric hindrance and high content of –SO3H per mass.

A novel hydroxyl polyacrylate latex modified by OvPOSS and its application in two-component waterborne polyurethane coatings

Octavinyl polyhedral oligomeric sisesquioxane (OvPOSS) was synthesized via hydrolysis and condensation of vinyltriethoxysilane. The structure of OvPOSS was determined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), 1H nuclear magnetic resonance and 29Si nuclear magnetic resonance. A novel hydroxyl functional polyacrylate latex (HPA) with core–shell structure modified by OvPOSS (OvPOSS/HPA) was successfully prepared via emulsion copolymerization. Consequently two-component waterborne polyurethane (2K-WPU) coatings were prepared by using the as-prepared latex as hydroxyl components and hydrophilic polyisocyanates as curing agents. The structure and properties of OvPOSS/HPA were marked by FTIR, XRD, differential scanning calorimetry and thermogravimetric analysis. The results of FTIR and XRD show that OvPOSS has been successfully embedded into HPA, and OvPOSS occupies a homogeneous distribution in the HPA matrix. The effect of OvPOSS on the properties of OvPOSS/HPA as well as the application performance of 2K-WPU coatings film were also investigated. The results show that OvPOSS/HPA possesses core–shell structure with the OvPOSS core and enhanced thermal stability. The glass transition temperature (Tg) of OvPOSS/HPA with 2.0% OvPOSS content is 22.3°C, which is 8.4°C higher than that of pure HPA. The performance properties of the 2K-WPU coating films such as pencil hardness were also improved by incorporation of OvPOSS.

Preparation and properties of super hydrophobic films from siloxane-modified two-component waterborne polyurethane and hydrophobic nano SiO2

Nanocomposite films with super hydrophobic surface were prepared by building rough micro/nano structure on the surface of siloxane-modified two-component waterborne polyurethane (2K-WPU) with hydrophobic nano SiO2. Firstly, nano SiO2 prepared by StÖber method with tetraethoxysilane (TEOS) as precursor was modified with trimethylethoxysilane (TMES), in order to cover a layer of hydrophobic methyl groups on the surface of nano SiO2. Then, a series of nanocomposite films with different water contact angles were obtained by adding different contents of TMES modified SiO2 into the siloxane-modified 2K-WPU. The effects of the content of nano SiO2 on the morphology and hydrophobicity of film surface were investigated. The results showed that the surface structures of the nanocomposite films became rougher and the water contact angle of nanocomposite films was increased obviously with the increase of the content of hydrophobic nano SiO2. Super hydrophobic nanocomposite film with water contact angle over 150° was successfully fabricated by using polysiloxane as low surface energy material and hydrophobic nano SiO2 as micro/nano rough structure builder on the polymer surface. Moreover, incorporating nano SiO2 into the 2K-WPU matrix could increase the glass transition temperature and thermal stability of the nanocomposite films.

Synthesis and characterization of alicyclic two-component waterborne polyurethane

PurposeThe purpose of this paper is to synthesize and characterize a series of alicyclic two-component waterborne polyurethane (2K-WPU) which is composed of non-ionic polyisocyanate aqueous dispersion and hydroxyl aqueous dispersion.Design/methodology/approachThe appearances of aqueous dispersions and 2K-WPU films were observed by photographs. The micromorphology of alicyclic polyisocyanate aqueous dispersion was examined by scanning electron microscopy (SEM). The molecule structures of WPU were studied by Fourier transform infrared (FTIR). The effect of NCO:OH molar ratio of two components and trimethylolpropane (TMP) content on the thermal stability, mechanical and water resistance properties of 2K-WPU films was studied.FindingsIt was found by SEM that alicyclic polyisocyanate particles in aqueous dispersion showed a kind of spherical particle appearance, in which hydrophobic polyisocyanate was encapsulated by hydrophilic ether linkages segment. FTIR showed that WPU was polymerized through mixture of polyisocyanate component and hydroxyl component and increasing NCO:OH molar ratio of two components from 1.1:1 to 1.5:1 had increased the content of urea, urethane and allophanate of 2K-WPU films. Increasing NCO:OH molar ratio had improved the mechanical and thermal properties of the 2K-WPU film, but the water resistance of the 2K-WPU film increased first and then weakened. Increasing TMP contents from 1 to 0.75 mol for 1:5 system had improved the mechanical, thermal and water resistance properties of the 2K-WPU film.Practical implicationsThe investigation established a method to prepare alicyclic 2K-WPU which is composed of non-ionic polyisocyanate aqueous dispersion and hydroxyl aqueous dispersion. The prepared 2K-WPU film could be applied in the field of waterborne surface coating, e.g. textile, wood and synthetic leather surfaces (Hasan et al., 2017; Akindoyo et al., 2016).Originality/valueThe paper established a method to synthesize alicyclic two-component 2K-WPU. The effect of NCO:OH molar ratio and TMP content on the thermal stability, mechanical and water resistance properties of 2K-WPU films were studied.