Characterization of an Aqueous Dispersion of a Hydrophilic Polyisocyanate for Waterborne Two-Pack Polyurethane Coatings

Zhou, Hang; Liu, Yang; Zhang, Margaret; Lu, Yijie; Arnett, Loryn P.; Soleimani, Mohsen; Winnik, Mitchell A.

doi:10.1021/acsapm.9b01173

Cited by 18 publications

(17 citation statements)

References 20 publications

(28 reference statements)

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“…20 nm) droplets accompanied by a small fraction of larger (ca. 90 nm) droplets, and that this size distribution is maintained over more than 20 h. 19 However, when a dispersion of hmPIC-Phen in water was mixed with a dispersion of hmPIC-Nben, we observed a high level of ET, indicating an exchange of molecules between the two types of dispersed droplets. This result can be rationalized by a molecular exchange mechanism in which the PIC molecules exit from their original nanodroplets, diffuse through the aqueous phase and enter into a different droplet.…”

Section: ■ Summary and Conclusionmentioning

confidence: 70%

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

et al. 2020

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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 (M n = 4200 g/mol, D̵ = 2, T g ≈ 15 °C) with a uniform hydrodynamic diameter (d h ) ≈ 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 (Φ ET = 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) (Φ ET = 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 Φ ET 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.

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Section: ■ Summary and Conclusionmentioning

confidence: 70%

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

et al. 2020

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“…In a previous report, we found that the dispersed hmPIC (diluted with 30 wt % THF) particles in the water had average diameters ( d ) on the order of 20–30 nm, accompanied by a smaller number of larger droplets (17 wt %, d ≈ 90 nm) that maintained their size and size distribution over more than 10 h. The fact that the PIC droplets are significantly smaller than Polyol-MAA latex particles ( d h ≈ 100 nm) enabled us to study their blends by DLS. The DLS signal intensity varies with the sixth power of the nanoparticle diameter so that in mixtures of the two components one sees only the signal from the polyol.…”

Section: Resultsmentioning

confidence: 90%

“…In a previous study, we examined aspects of film formation in a model WB 2KPU system consisting of an acrylic polyol and a hydrophilically modified PIC (hmPIC). The hmPIC used in these studies is a partial modification of a trimerized HDI–polyisocyanate that also contains tetramer, pentamer, heptamer, and high molecular weight homologues leading to a mixture of hmPIC and unmodified PIC (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

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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 carboxylfunctional acrylic polyols (M n ≈ 5000 g/mol, Đ ≈ 2.7, T g ≈ 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.

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“…For decades, due to the concern of human beings about the limited fossil resources and the warming climate environment, coupled with the government restrictions and the harm to the environment and human body, [1][2][3] the conventional polyurethane coatings, which containing volatile organic compounds (VOCs), have been unable to meet the needs of social development. 4,5 Waterborne polyurethane (WPU) coating, as a green waterborne coating product, 6,7 is widely used for its excellent properties such as environmental protection, non-flammability, high flexibility, and good structural controllability. [8][9][10][11] However, due to the hydrophilic groups and linear structure in its chain, WPU has some inherent disadvantages, such as slow curing efficiency, poor mechanical strength, and water sensitivity.…”

Section: Introductionmentioning

confidence: 99%

Preparation and properties of green UV‐curable itaconic acid cross‐linked modified waterborne polyurethane coating

Dong

Ren

Duan

et al. 2021

J of Applied Polymer Sci

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Waterborne polyurethane (WPU) coating, as a kind of green product, can replace solvent polyurethane coating, but its application in the field of coating is limited since its defects such as slow curing efficiency, low strength, and water resistance. In this study, a trifunctional itaconic acid-based crosslinking agent (IHA) was synthesized from itaconic acid and hydroxyethyl acrylate. A series of green UV-curable WPU coatings were prepared by introducing IHA into WPU prepolymer in different proportions (2.5 $ 10 wt.%). IHA posed as crosslinking agent in WPU, which can not only enhance strength, but also accelerate curing rate in WPU coatings. The results demonstrated that the gel content and hydrophobic angle of the modified WPU coating (WPU-IHA) are increased by 25.6% and 34.8 , respectively, indicating a good water resistance.Most notably, due to the increase of crosslinking degree and the decrease of chain mobility, the UV-curable WPU coating shows excellent mechanical properties with 21.9 MPa in tensile strength and a pencil hardness of 5H, which is substantially higher than that of pure WPU coatings. Therefore, the IHA shows great potential to substitute petroleum-based crosslinking agents in the preparation of environmentally friendly UV-curable WPU coatings with high strength and good surface scratch hardness.

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Characterization of an Aqueous Dispersion of a Hydrophilic Polyisocyanate for Waterborne Two-Pack Polyurethane Coatings

Cited by 18 publications

References 20 publications

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

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

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

Preparation and properties of green UV‐curable itaconic acid cross‐linked modified waterborne polyurethane coating

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