Polyurethane Coatings Research Articles

Insight into Degrading Effects of Two Fungi on Polyurethane Coating Failure in a Simulated Atmospheric Environment.

Two different fungi, Talaromyces funiculosus (T. funiculosus) and Phanerochaete chrysosporium (P. chrysosporium), were collected from the Xishuangbanna atmospheric corrosion site and incubated on a polyurethane (PU) coating at 30 °C for two weeks under 95% relative humidity (RH). The biodegrading effects of these fungi on the coating failure were investigated from aspects of metabolism and electrochemistry. The results showed that T. funiculosus contributed more to the degradation of the PU coating failure than P. chrysosporium, and two factors played dominant roles. First, the weight of the T. funiculosus mycelium was nearly 3 times more than that of P. chrysosporium, indicating there was more substrate mycelium of T. funiculosus deep into the coatings to get more nutrition in atmospheric during colonization. Second, T. funiculosus secreted carboxylic acids, such as citric, propanoic, succinic, and tartaric acids, and accelerated the hydrolysis of the ester and urethane bonds in the PU coatings. As a result, the mycelium of T. funiculosus readily penetrated the interface of the coating and substrate resulting in a rapid proliferation. Thus, the |Z|0.01Hz value of the coating decreased to 5.1 × 104 Ω·cm2 after 14 days of colonization by T. funiculosus while the value remained at 7.2 × 107 Ω·cm2 after colonization by P. chrysosporium. These insights suggest that the biodegradation process in simulated atmospheric environments would provide theoretical guidance and directions for the design of antifungal PU coatings.

Anti-Fouling and Anti-Biofilm Performance of Self-Polishing Waterborne Polyurethane with Gemini Quaternary Ammonium Salts.

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.

Preparation and properties of water‐based photochromic polyurethane coatings containing Er(III)‐doped WO3

Photochromic coatings have been widely used in many fields such as architecture, transportation, and military because of the combination of reversible color‐changing properties with the insulation and protection of substrates. Conventionally, organic photochromic components are used for the preparation of photochromic coatings with fast photo‐response and excellent fatigue resistance, but the preparation of these coatings is costly and time‐consuming. Here, we have developed a relatively simple and cost‐effective strategy for the preparation of water‐based photochromic polyurethane coatings. Er(III)‐doped WO3 was synthesized and used as the photochromic component for the preparation of polyurethane/Er(III)‐doped WO3 composites, which were further used for the preparation of photochromic coatings. The properties of the coatings were tested and characterized. Due to their excellent thermal stability, water resistance, fatigue resistance, and photochromism, these coatings might have practical applications in various areas.

Enhanced Anticorrosive Properties of Silane Functionalized Polybenzoxazine @CeO2 Nanocomposites with Polyurethane Coatings on Mild Steel

In this study, the durability of polyurethane adhesives are successfully developed using silane-functionalized polybenzoxazine@CeO2 nanocomposites. The electrochemical measurements were used to investigate the mechanical strength of polybenzoxazine nanocomposite with polyurethane materials. The superior results in the process of passivation film that also controlled the dissolution of metal have been characterized by UV-visible, XRD, SEM/EDX, FT IR, TGA-DTA-DSC, micro hardness, gel absorption and water absorption analyses. The mechanical performance of the coated surface that supported up the electrochemical investigations was enhanced by the incorporation of silane functionalized polybenzoxazine@CeO2 nanocomposites with polyurethane. The use of ployurthane in the TGA process increases the cross-linked density of the coating, resulting in high thermal stability. As a result of their superior anticorrosive property, the proposed polybenzoxazine@CeO2 nanocomposites with polyurethane films offer the openings for the development of unique, state-of-the-art anticorrosive adhesives across a wide range of sectors.

Selective chemical disassembly of elastane fibres and polyurethane coatings in textiles

Solvolysis of elastane in blended fabrics using tert-amyl alcohol and KOH (cat.) provides elastane monomers and a fibre matrix. The process is especially useful for polyamide/elastane blends, providing a possibility for fibre-to-fibre recycling.

Anti-Icing Behavior of Polyurethane Coatings: A Thorough Understanding of the Relationship between Physicochemical Properties and Ice-Adhesion

Anti-Icing Behavior of Polyurethane Coatings: A Thorough Understanding of the Relationship between Physicochemical Properties and Ice-Adhesion

Controlled-release fertilizers with an ultralow coating content

The controlled-release fertilizers with superior controlled-release performance and an extremely low coating content were fabricated using castor oil-based polyurethane coatings, followed by dual superhydrophobic modification.

Self-healing polyurethane-polypropylene oxide copolymers for the protection of carbon and glass fiber-reinforced composites

Polyurethane-polypropylene oxide block copolymers containing fragments of an adduct capable of self-healing by the Diels-Alder reaction mechanism have been synthesized and studied for the first time. All obtained polyurethane copolymers were characterized by IR spectroscopy. The temperature transitions and thermal stability of copolymer melts were determined by using the methods of differential scanning calorimetry and thermogravimetric analysis. The self-healing effect was confirmed using a thermal cycling procedure on pre-damaged samples of modified polyurethanes and surface morphology studies. The perspective of the work begun on the creation of self-healing protective polyurethane coatings are shown.

ПОЛУЧЕНИЕ И ПРИМЕНЕНИЕ ГИДРОФОБНЫХ ПОЛИУРЕТАНОВЫХ КРЕМНИЙСОДЕРЖАЩИХ ПОКРЫТИЙ. ЧАСТЬ 2. (ОБЗОР)

It is well known, that water drops tend to easily flow down from lotus leaves because of low wetting degree. In the first part of the review, we discussed the basic concept of wetting theory and different limits of existing models. The unsolved questions in the theory of wetting did not slow the development of methods of hydrophobic coatings fabrication. At present, coatings with low wetting degree are implemented in different industry fields. However, fabrication of coatings with stable hydrophobic properties is still difficult. That problem is especially serious for highly- and superhydrophobic coatings. The second part of the review describes the methods of fabrication of hydrophobic, highly- and superhydrophobic polyurethane coatings. We briefly mention the chemical reactions, which lead to polyurethanes obtaining, methods of hydrophobic coatings fabrication, and their application fields. Special attention is focused on the analysis of the surface parameters in order to establish general laws for producing hydrophobic, highly-hydrophobic and super-hydrophobic polyurethane silicon coatings

Color and Gloss Changes of a Lignin-Based Polyurethane Coating under Accelerated Weathering

Color and Gloss Changes of a Lignin-Based Polyurethane Coating under Accelerated Weathering

Thermal evaluation of a room coated by thin urethane nanocomposite layer coating for energy-saving efficiency in building applications

Today, it is common to use thin-layer nanocomposite coatings as insulation to reduce heat loss through building walls. One of the important advantages of these coatings is preventing energy loss as a thermal barrier in low thicknesses and with high efficiency. Investigations on the energy loss and saving of coated buildings are often practiced using numerical and experimental approaches. In this study, numerical simulation and experimental evaluation consisting of modification of nanoparticles and preparation powder coating nanocomposite, are used to study the effects of coated polyurethane nanocomposite containing nano Al2O3 and nano ZrO2 on both sides of the walls of a sample room on temperature distribution and heat transfer. For this purpose, a three-dimensional enclosure was assumed as a room having a radiant cooling panel, which is modeled under various features of the walls' interior and exterior coating. To determine the flow and temperature fields, the governing equations that include the continuity, momentum, turbulence, and energy equations, which are coupled through the buoyancy term, have been solved using the Fluent software. The SIMPLE algorithm to accommodate the pressure-velocity coupling, the k-ε model for turbulence modeling, the Boussinesq approximation for buoyancy term modeling, and the DO model for radiation simulation, are employed. The results of the thermography of the samples showed that the temperature reduction in the samples containing zirconium oxide compared to aluminum oxide had a better performance in the thermal insulation of the coating and the lowest temperature was observed in the nanocomposite containing 3% zirconium oxide. Numerical studies showed that this thin layer nanocomposite coating reduces energy consumption by 4% and 13%, respectively, compared to pure polyurethane coatings and acrylic paints.

A Self-Matting Waterborne Polyurethane Coating for PVC Artificial Leather

A type of polyester-based self-matting waterborne polyurethane (ESMWPU) with an excellent matte effect of 0.8° and transmittance of 78.5% for PVC artificial leather was synthesized. The influence of synthesis parameters, including R value, crosslinking and hydrophilic group content, on coating gloss and transmittance was investigated. Meanwhile, the properties necessary for applying water-based resins to plasticized PVC were detailed. The results demonstrated that R value, crosslinking degree and hydrophilic group content synergistically decided the morphological changes of latex particles during their film-forming process in three aspects: particle stiffness, three-dimensional structure and particle size, respectively. With optimized parameters of R = 1.9, TMP = 2 wt% and DMPA = 1.75 wt%, ESMWPU latex particles stabilized their spherical shapes without collapsing in the film-forming process and created a rough surface, resulting in a matte effect. In terms of application performance, good wetting and adhesion for ESMWPU to a plasticized PVC surface was achieved with a 2 wt% leveling agent load. Moreover, due to the high cohesion energy of ester bonds and intermolecular hydrogen bonds, this type of polyester-based ESMWPU also depicted admirable thermal adhesion resistance. All aforementioned results distinctly demonstrate a feasible yet promising paradigm for applying ESMWPU on PVC artificial leather.

Fabrication of Superhydrophobic Coating Based on Waterborne Silicone-Modified Polyurethane Dispersion and Silica Nanoparticles.

In this work, eco-friendly superhydrophobic coatings were prepared by dispersing hydrophobic silica nanoparticles and a waterborne silicone-modified polyurethane dispersion into an ethanol solution, which was free of fluorine and volatile toxic solvents. The effects of the silica content on the hydrophobicity and scratch resistance of the hydrophobic surfaces were investigated by WCA measurements and a sandpaper abrasion test, respectively. The experimental results indicated that when the silica content exceeded 30% by mass, the silica/silicone-modified polyurethane coatings had superhydrophobicity. Meanwhile, the superhydrophobic coatings with a silica content of 30% by mass simultaneously had the optimal mechanical stability. We studied the morphology and roughness of the hydrophobic surfaces with different silica content and attempted to briefly explain the influence mechanism of silica content. Furthermore, anti-icing and oil-water separation experiments were carried out on the superhydrophobic coatings, which exhibited good anti-icing performance and high separation efficiency. The eco-friendly superhydrophobic coating is expected to be applied in the fields of oil-water separation, anti-icing, and self-cleaning, etc.

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.

Selective Solvolysis of Bio-Based PU-Coated Fabric.

Polyurethane (PU) coatings are widely applied on high performing textiles due to their excellent durability and mechanical properties. PUs based on renewable resources were developed to improve the environmental impact of coatings by decreasing the carbon footprint. However, at the end-of-life, PU-coated textiles still end up as landfill or are incinerated since PUs are not biodegradable and are not being recycled at this moment. Therefore, the recycling of PU-coated substrates needs to be examined. This study reports the selective solvolysis of a polyester (PET) fabric coated with a bio-based PU using a 70% ZnCl2 aqueous solution. This method allowed the easy separation of the coating from the fabric. The thermal, chemical and mechanical characteristics of the virgin PET and recycled PET were examined via tensile strength tests, IR, TGA, DSC and GPC. Analysis of the fractions after solvolysis revealed that the PU was converted into the original polyol and an amine, corresponding to the isocyanate used for PU synthesis.

Influence of modified graphene oxide on the antifouling performance of waterborne polyurethane coatings containing amphiphilic honeycomb surface

Influence of modified graphene oxide on the antifouling performance of waterborne polyurethane coatings containing amphiphilic honeycomb surface

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

Waterborne polyurethane (WPU) coatings are widely used for the protection of cement-based materials by reducing surface permeability. However, poor mechanical property and moisture permeability caused by good hydrophilicity of WPU coatings limit the protecting application for building engineering. This work has investigated the effect of reinforcing WPU coating with polyaniline/lignin (PL) in protecting cement-based materials. Through the XRD, FT-IR and SEM characterizations, the successful preparation of PL complex has been proved. After the reinforcing of WPU coating by PL, the mechanical property and water contact angle has increased from 1.63 MPa to 2.07 MPa (by 26.99%), and from 72.1° to 116.5° (by 61.58%), respectively. Besides, as shown by capillary water absorption test, the impermeability of mortar with PL-modified WPU (LWPU) coatings has improved, and the capillary water absorption of mortar samples with LWPU coatings at 8 days decreased from 0.3074 mm3/mm2 to 0.1763 mm3/mm2 (by 42.65%). As a result of barrier effect and increased hydrophobicity, the rapid chloride migration (RCM) coefficient of mortar samples with LWPU coatings decreased from 8.52*10−12 m2/s to 6.34*10−12 m2/s by 25.59%. This study demonstrates that PL composites could be used as an effective additive to enhance WPU coating performance in protecting cement-based materials. Such green and effective waterborne coating shows great promises in civil engineering applications.

Preparation of new full UV-absorbing carbon dots from quercetin and their application in UV-absorbing systems for waterborne polyurethane coatings

In this paper, a kind of novel fully UV absorbing carbon dots (QC-CDs) were prepared as UV absorbers by a one-step hydrothermal method using quercetin as raw material. The prepared QC-CDs have high absorption efficiency (over 98%) in the whole ultraviolet region (200–400 nm), and are almost completely transmitted in the visible light region. The prepared QC-CDs have good stability and resistance to photobleaching. After the treatment with different pH and temperature, the QC-CDs maintained good absorption stability. QC-CDs have a wider UV absorption range than commercial water-soluble organic UV absorbers-BP-4. In terms of aging resistance, QC-CDs can achieve the same effect as BP-4. After subjecting QC-CDs and BP-4 to different pH values, it was found that QC-CDs remain fully UV absorbing at different pH conditions and maintain good absorption stability, but BP-4 loses its function as a UV absorber under alkaline conditions. Then, the UV absorption mechanism of QC-CDs has also been investigated and applied to the UV absorption systems of waterborne coatings PU. Finally, the QC-CDs@PU with full UV absorption properties was applied in the photodegradation prevention experiment of Rhodamine B. At present, the preparation process of QC-CDs is simple and environmentally friendly. QC-CDs have the potential to become a new generation of water-soluble UV absorbers.

Corrosion-resistant polyurethane coatings from structure-homogenized biorefinery lignin through fractionation and oxypropylation

Using lignin for polyurethane (PU) synthesis is challenging because of its heterogeneous structure, i.e., broad molecule weight (MW) distribution and diverse hydroxyl (OH) functionality. This complexity influences the crosslinking reaction between lignin and isocyanate and affects the quality of PU products. Here, we propose a two-step strategy for lignin structure homogenization by lowering its MW, while narrowing the MW distribution (step 1), and achieving uniform OH functionality (step 2). Step 1 involves a bioethanol fractionation process, yielding fractionated lignin with one order lower MW than the raw lignin while exhibiting better processability for the subsequent process. Step 2 is performed by an oxyalkylation process using fractionated lignin that converts phenolic and carboxylic OHs to aliphatic OHs. As a result, we obtained structure-homogenized lignin with good compatibility and crosslinking with hexamethylene diisocyanate for PU coating synthesis. Moreover, PU coatings prepared from structure-homogenized lignin display a defect-free microscopic structure and show better corrosion resistance than coatings fabricated from its raw lignin alternative. Overall, the structure homogenization process is a beneficial way of using lignin as biopolyol in PU synthesis toward the application-oriented design of corrosion-resistant lignin-based PU coatings.

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.