Enhancing the protective performance of waterborne polyurethane coatings by non-covalent functionalized MXene

Effects of nanoparticulate silver on the corrosion protection performance of polyurethane coatings on mild steel in sodium chloride solution

Investigation on the effects of polyaniline/lignin composites on the performance of waterborne polyurethane coating for protecting cement-based materials

Environmentally friendly waterborne polyurethane (WPU) coatings are used extensively due to their low VOCs emission than solvent based PU coatings. Additionally, WPU coatings have low temperature flexibility, pH stability, water resistance, superior solvent resistance, outstanding weathering resistance and desirable chemical and mechanical properties. This review provides an overview on the recent developments of WPU coatings and their value added applications in the coatings and paint industry. UV-cured WPU coatings provide an important class of green and ecofriendly coatings with outstanding mechanical properties and rapid curing system. Hyper-branched polyurethanes (PUs) show interesting properties, such as high solubility, reactivity and good rheological behavior owing to multiple end groups, compact molecular structure and diminishing chain entanglement. Inherently, WPU coatings have reduced stiffness and mechanical strength that can be increased by the addition of nanoparticles, like Ag, Cu, TiO2, SiO2 and many more. Fire retardants, commonly phosphorous, are incorporated in the WPU structure to increase the flame retardancy of WPU coatings.

Topography and wettability plays an important role to fouling release performance of a coating. Surface morphology and water contact angles (WCA) depending on time of three waterborne polyurethane (WPU) coatings were studied by laser scanning microscope and optical contact angle meter. The results show that WPU coatings with low hard segment content are consisted of hard segment domains, soft segment domains and crack-like non-cohesive regions. With increasing hard segment content, nanostructured micro-phase separated topography is easier to forming, and crack-like non-cohesive regions is reduced. A stable hydrophobic surface in the WPU system can be obtained by drying coating at 60C as well as adding hard segment content to improve fouling release performance of the coatings.

In this study, waterborne polyurethane (WPU) coatings were modified by adding various compositions of nano‐boron carbide (nano‐B4C) particles. In order to achieve proper dispersion of nano‐B4C in WPU and increasing chemical interactions between them, the nano‐B4C particles were treated with polyethylene glycol (PEG) or polypropylene glycol (PPG). The modified surface and microstructure of nano‐B4C were characterized by Fourier transform infrared, scanning electron microscopy and transmission electron microscopy. The deposition experiment was designed to evaluate the dispersion effect of nano‐B4C in PEG or PPG aqueous solution. The physical performance of nano‐B4C modified WPU coatings was measured following the national standards of paints and vanishes. The results revealed that the PEG6000 not only enhanced the interaction between nano‐B4C and WPU but also exhibited a remarkable ability to improve the physical performance of WPU coating. The coating with 15 wt% of nano‐B4C addition exhibited the best performance in terms of abrasion and hardness, which could be attributed to the best uniform dispersion of nano‐B4C particles in PEG6000 aqueous solution.

In this study, an eco-friendly coconut oil-based polyol blend was synthesized for bio-based waterborne polyurethane (WBPU) and WBPU-silane composite coatings. It was demonstrated that an increase in silane content incorporated into the WBPU matrix significantly enhanced the corrosion protection of WBPU coatings. Results also show a fourfold increase in the adhesion strength of WBPU-silane composite coatings as compared to that of bare WBPU coatings. Further, the water contact angle revealed that hydrophobic properties increase as the silane content incorporated into the WBPU matrix increases. This work provides a novel route for enhanced corrosion protection utilizing a bio-based polyol blend.

Waterborne polyurethane (WPU) coatings have gained significant attention in the industry due to their low environmental impact and excellent properties. Furthermore, the UV-curing system reduces energy costs and enhances curing efficiency. Hence, exploring the UV-curable WPU system is essential for advancing the next generation of coatings. In this study, a 2K WPU system was developed by functionalizing isocyanate-terminated polyurethane with thiol and vinyl groups. The coating was cured under UV light through a thiol-ene click reaction, and the effects of photoinitiator content on the coating performance were investigated. The feasibility of sunlight curing for this WPU coating was also assessed. The results showed that while photoinitiator content had a slight impact on UV-cured WPU coatings, it significantly affected sunlight-cured WPU. Also, with the appropriate photoinitiator content, sunlight-cured WPU could achieve comparable performance to UV-curable ones.

A castor oil (CO) was modified via thiol‐ene click chemistry reaction between CO and 3‐mercaptopropyl trimethoxysilane, with the conversion of CC bonds of CO over 99% based on1HNMR spectra. The obtained modified castor oil (MCO) was used as a biobased polyol to prepare waterborne polyurethane (WPU) dispersions. The modification of CO exhibited a great effect on the properties of WPU dispersions and coatings, and an obvious change is the improvement of the water resistance of WPU coatings. WPU dispersions with MCO had good storage stability. A WPU coating with 7% MCO had high surface hydrophobicity, and its water absorption was as low as 3.2%. Conductive carbon black filled WPU coatings with MCO were cured by efficient UV radiation, and their conductive percolation threshold could decrease to 0.76%, which could be attributed to the well filler dispersion and strong filler‐polymer interaction. The WPU dispersions are ecofriendly, and can be used to produce biobased WPU coatings with a great application potential in antistatic coating fields.

Facile fabrication of waterborne polyurethane coatings with good hydrophobicity and antifouling properties by leveraging fluorinated polysiloxane

Bio-polyols based waterborne polyurethane coatings reinforced with chitosan-modified ZnO nanoparticles

Matte waterborne polyurethane fabric nanocoating with versatility via mono-layered montmorillonite nanosheets

Giving waterborne polyurethane (WPU) coatings self-healing properties not only maintains the coating's environmentally friendly characteristics but also extends the material's service life and enables sustainable development. Therefore, self-healing WPUs have received an increasing amount of attention from researchers. However, it is a serious challenge to overcome the original shortcomings of WPU coatings, such as poor strength, low hardness, and weak adhesion, as well as the introduction of self-healing properties resulting in further degradation of strength-mechanical properties and heat resistance. Here, we provide a design strategy to introduce a noncovalent physical cross-linking network based on cation-π interactions into the WPU molecular structure to prepare a series of self-healing transparent WPU coatings with high strength. The coating exhibited a very high tensile strength (66.11 ± 3.28 MPa) and excellent flexibility (0.5 mm), with a scratch repair efficiency of up to 98.2% for 12 h of repair at 60 °C. In addition, the coating also has good optical properties and has broad application prospects in the fields of transparent protective coatings and adhesives.

Developing multifunctional coatings with excellent mechanical and thermal properties is highly desirable for wood-based composite application. The recent development of waterborne coatings for wood products suggests that a promising thermosetting material needs to also have properties like low volatile organic contents (VOCs), hardness, and fast curing. The cellulose nanocrystals/graphene materials (CNC/GM) sols were prepared through the one-step method as the thermally conductive and reinforced modifier for preparing waterborne polyurethane (WPU) coatings. The influence of this modifier on the thermal and mechanical properties such as thermal conductivity, abrasion resistance, and adhesion of WPU coatings was investigated. The results indicated that adding CNC/GM sols increased the hardness, abrasion resistance, and thermal conductivity of the WPU coatings, and meanwhile maintained the coating adhesion at the highest grade (level 1). The highest abrasion resistance value of 0.023 g/100 r was obtained for the modified WPU coating when the addition of GM was 3%.

Traditional waterborne polyurethane (WPU) coatings are limited in use due to its low crosslink density and poor adhesive properties. In this study, four types of toluene diisocyanate-functionalized graphene oxide (TGO-1, TGO-2, TGO-3, and TGO-4) were prepared and used as fillers for anti-corrosion coatings to improve the anticorrosion performance of WPU coatings. Their structure were characterized by XRD, FT-IR, Raman, and SEM. Electrochemical tests indicated that the WPU coating containing 0.3 wt% TGO-2 exhibited the highest |Z|0.01HZ and R t values and possessed the best anticorrosion performance. It was primarily attributed to the excellent physical barrier effect of graphene oxide which was grafted onto polypropylene, improving its dispersibility in coatings.

Biofilms are known to be difficult to eradicate and control, complicating human infections and marine biofouling. In this study, self-polishing and anti-fouling waterborne polyurethane coatings synthesized from gemini quaternary ammonium salts (GQAS), polyethylene glycol (PEG), and polycaprolactone diol (PCL) demonstrate excellent antibiofilm efficacy. Their anti-fouling and anti-biofilm performance was confirmed by a culture-based method in broth media, with the biofilm formation factor against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli) for 2 days. The results indicate that polyurethane coatings have excellent anti-biofilm activity when the content of GQAS reached 8.5 wt% against S. aureus, and 15.8 wt% against E. coli. The resulting waterborne polyurethane coatings demonstrate both hydrolytic and enzymatic degradation, and the surface erosion enzymatic degradation mechanism enables them with good self-polishing capability. The extracts cyto-toxicity of these polyurethane coatings and degradation liquids was also systematically studied; they could be degraded to non-toxic or low toxic compositions. This study shows the possibility to achieve potent self-polishing and anti-biofilm efficacy by integrating antibacterial GQAS, PEG, and PCL into waterborne polyurethane coatings.