Environment-friendly Waterborne Research Articles

Environment-friendly waterborne fire retardants for protection of wood and bark against fire flames

Flame retardancy was induced in maple (Acer velutinum) and ash (Fraxinus excelsior) wood and bark by means of mixtures consisting of bio-based materials such as starch (S) and glue (G) and water-based paint, MINWAX (M) in two different combined formulations with perlite (P) as the main fire retardant. The selected wood species as solid wood with two different treatable surfaces (with and without bark) were examined. The lowest and the highest mass loss occurred in the untreated-ash and untreated-maple wood samples with bark, while the lowest weight percent gain was related to PSGM-treated ash wood samples with bark, and the highest weight percent gain was related to PSGM-treated maple wood samples without bark. The lowest time to ignition and glowing point time were measured in the untreated-maple wood samples without bark, and the highest of them were measured in the PSGM-treated ash wood samples without bark. The effect of bark in the treated- and untreated-maple samples on the time to ignition and glowing point time was greater than the bark of treated- and untreated-ash samples, respectively. There was not any significant relationship between actual retention, weight percent gain, and mass loss for all treatments. However, there was significant difference between the individual and interaction agents on fire retardancy of treated and untreated samples.

Research on rheological properties and modification mechanism of waterborne polyurethane modified bitumen

Polyurethane (PU) based materials are emerging as asphalt modifiers due to their unique molecular structure, but the production of commonly used PU prepolymers and PU elastomers might pose environmental and safety risks. In this work, environment-friendly waterborne polyurethane (WPU) additives were prepared and employed to modify bitumen. The properties of the WPU additive were characterized first. Then, the storage stability, workability, and rheological properties of the modified bitumen containing different dosages of WPU additives were investigated. The modification mechanism of the WPU on virgin bitumen was also analyzed. The Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) experimental results indicate that WPU with two glass transition temperatures (Tg) without toxic terminal groups was successfully prepared. Additionally, the excellent storage stability and workability of the WPU modified bitumen can be observed with the dosages of WPU additives no more than 9 wt%. Dynamic shear rheometer results show that WPU additives enhanced the deformation resistance of bitumen in high-temperature environments. The improvement of the anti-cracking ability of WPU modified bitumen at low-temperature environments was also verified by the bending beam rheometer experiment. However, the fatigue resistance of bitumen was slightly weakened by WPU. FTIR analyses for modified bitumen prove that the incorporation of WPU additives didn’t change the chemical structure of virgin bitumen. The enhanced high-temperature and low-temperature performance of the WPU modified bitumen can be attributed to the two-phase structure of the WPU molecular chain. Overall, the eco-friendly bitumen additive applied in this study has excellent application value and broad market prospects.

Multifunctional waterborne polyurethane nanocoatings based on large-scale exfoliated mono-layered montmorillonite nanosheets

Ultrathin two-dimensional (2D) nanosheets have driven the development of multifunctional materials. However, persistent challenges with complex processes, low production rates, and high costs have prevented ultrathin 2D nanosheets from realizing their full potential in nanocomposite. Herein, large-scale exfoliated montmorillonite (MTM) mono-layered nanosheets in polyethyl-phosphate glycol ester were assembled into environment-friendly waterborne polyurethane to obtain multifunctional nanocoatings with superior matte performance, favorable flame retardancy, and high adhesion. Specifically, a significant 98.2 % decrease of 60° gloss from 65.0 GU to 1.2 GU was observed, which almost wholly diffuses incident light due to the rougher surface. Besides, total heat release and total smoke rate were decreased by a maximum of 27.1 % and 34.4 %, respectively. Surprisingly, the nanocoating with excellent anti-blocking properties has outstanding adhesion to PU leather. These nanocoatings on leather and fabric showed potential for engineering applications. This study may provide new insight for application of ultrathin 2D nanosheets in multifunctional materials.

Fabrication and performance of nitrocellulose nanoparticles reinforced environment-friendly waterborne ethyl cellulose (Surelease®) nanocomposites

In terms of eco-friendly materials, cellulose-based nanomaterials have received widespread attention as nano-functional fillers due to their lower production costs, better biodegradability, and excellent interfacial compatibility with polymers. In this paper, a nitrocellulose (NC) nano aqueous dispersion was successfully prepared using a simple, low-energy solvent displacement method. The effect of the organic: aqueous phase mixing order and kinetics, organic solvent, stirring speed, and organic: aqueous phase mixing ratio on the particle size and polydispersity index (PDI) of the nanoparticles were investigated. The obtained NC dispersion had a small particle size (Z-average particle diameter (Zave) < 100 nm), uniform size distribution (polydispersity index (PDI) < 0.2), and relatively good stability (Zeta potential is about −30 mV). And a series of Surelease® nanocomposites incorporated with various content of NC nanoparticles were fabricated via a facile solution casting/solvent evaporation method. The micromorphology, chemical structure, thermal properties, and water vapor sorption behavior of the nanocomposites were systematically investigated by Field scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectrometer, Differential scanning calorimetry, Thermogravimetric analysis, and dynamic vapor sorption technology. The results show that the nanocomposites have good resistance to moisture absorption (<3 %) and effective thermal properties.

Sonochemical Approach of Highly Thermal, Mechanical, and Corrosion Inhibition Performance of Metal–Organic Framework (ZIF‐8)‐Decorated Waterborne Polyurethane Nanocomposite

Herein, highly porous metal–organic framework (ZIF‐8)‐decorated environmental friendly waterborne polyurethane (WPU) (ZIF‐8@WPU) nanocomposites via facile sonochemical technique are synthesized. The ZIF‐8@WPU shows threefold excellent mechanical performance (tensile strength ≈23 MPa and elongation 670%) at a very low 2.5 wt% filler loading compared to pristine WPU. In addition, the synthesized ZIF‐8@WPU exhibits high thermal stability and water vapor permeability properties with increasing nanofiller concentration. Interestingly, the incorporation of ZIF‐8 into WPU potentially improves the corrosion inhibition performance with a superior corrosion rate (υcorr) 1.7 × 10−2 mm year−1 and ≈94% protection efficiency (PE) at lower filler (2.5 wt%) loading, attributing to the facile synthesis methods, internal structural arrangement, well interaction of filler and matrix, high surface area, and tuneable pore size of filler material. The crystallinity of ZIF‐8 and ZIF‐8@WPU is analyzed by powder X‐ray diffraction, morphology by scanning electron microscopy, thermal properties by thermogravimetric analysis, and mechanical properties by the universal testing machine. This new insight has potential toward the green approach for synthesizing and structural engineering high‐performance advanced nanocomposites in the coating, breathable devices, and food packaging industrial utilization.

An “inner soft external hard”, scratch-resistant, self-healing waterborne poly(urethane-urea) coating based on gradient metal coordination structure

To reduce pollution and maintain sustainable development, environmental friendly waterborne coatings as a replacement for conventional oil-based coatings have drawn lots of attention and been widely studied recently. It is a challenge to overcome the inherited weakness of waterborne coatings including poor scratch-resistance, low hardness and short lifespan. Herein, we have developed a scratch-resistant and self-healing waterborne coating of poly(urethane-urea), which contains a dual metal coordination structure of Zn(II)-carboxyl and Zn(II)-diamidepyridine by using the method of ions penetration. The addition of zinc ions has given dense metal coordination bonds on the coating surface, which has greatly increased the surface hardness (from B to 4H) and scratch-resistance, while the inner layer keeps excellent adhesion (>1.5 MPa) to substrates because of less metal ion penetration to the inner. What's more, the coating exhibits outstanding self-repairing performance, and the repair ability is better under hygrothermal condition. Atomic force microscope (AFM), dynamic mechanical analysis (DMA) and thermal analysis were used to characterize the self-healing and hardening mechanisms of the coatings. These results are expected to provide a useful method to improve the overall strength of waterborne coating.

Facile and high-concentration exfoliation of montmorillonite into mono-layered nanosheets and application in multifunctional waterborne polyurethane coating

A large-scale exfoliation method to obtain high-quality and mono-layered montmorillonite (Mt) nanosheets via the aggregation of polyethyl-phosphate glycol ester (Exolit OP 550) was proposed. Small-angle X-ray diffraction (XRD), transmission electron microscope (TEM), selected area electron diffraction (SAED), and atomic force microscopy (AFM) examinations indicated that 30.0 wt.% of layered Mt. were exfoliated into mono-layered nanosheets in Exolit OP 550 after a mechanical stirring process at 60 °C for 12 h. This exfoliation concentration was increased by 67–650% compared with that of other works. The Mt. nanosheets with Exolit OP 550 were then assembled into environment-friendly waterborne polyurethane (OPWPU) coating by in situ polymerization. A significant decrease of 60° gloss, from 30.2 GU to 0.3 GU, was observed. Many large, uniform, and continuous spherical particles on the surface of OPWPU nanocoatings were found by scanning electron microscopy (SEM), which resulted in a rough surface that almost completely diffused incident light. Besides, limiting oxygen index (LOI), cone calorimeter testing (CCT), and SEM results suggested that the OPWPU nanocomposites also had improved fire retardancy, especially the peak heat release rate was decreased by a maximum of 39.2%. This study may open up new possibilities for the application of Mt. nanosheets in polymers.

Effect of γ-aminopropyltriethoxysilane on the properties of cellulose acetate butyrate modified acrylic waterborne coatings

Novel waterborne acrylic resin modified by cellulose acetate butyrate was successfully synthesized by a homogeneous solution polymerization with 2-butoxy ethanol, cellulose acetate butyrate and acrylic monomers as raw materials, N, N - dimethyl ethanolamine as neutralization and γ-aminopropyltriethoxysilane (KH-550) as curing agent. The influences of the cellulose acetate butyrate and curing agent content on the properties of the waterborne acrylic resin were investigated. As a curing agent, KH-550 not only improved the cross-linking density of the resin effectively, but also bonded to the substrate to form a molecular layer of silane. Cellulose acetate butyrate and KH-550 were found to reduce the curing temperature of the resin. The tensile strength of the coating added with the curing agent (5.89 MPa) was significantly improved compared to that of cellulose acetate butyrate modified resin (1.49 MPa). This kind of environment-friendly waterborne acrylic resin has a strong potential application in wood coatings, automobile coatings and other fields.

Synthesis, kinetics and characterization of environment friendly waterborne acrylate copolymers

The copolymers consisting of acrylic and methacrylic esters have achieved prime importance due to their versatile environment friendly applications. Copolymerization of Methyl methacrylate (MMA) with suitable vinyl monomers such as alkyl acrylate and methacrylate has been carried out for modifying the properties of the polymer. In current research synthesis of waterborne copolymer of MMA and 2- Ethyl hexyl acrylate (2-EHA) carried out by ecofriendly emulsion polymerization technique and the kinetics of polymerization, characterizations of the copolymers have been studied. Synthesized copolymers were characterized by FTIR, NMR, DSC, and TGA. The kinetics results of the MMA-co-EHA copolymer was compared with the previously synthesized copolymer MMA with Butyl acrylate (BA). On comparing these results, it was found that EHA gives higher conversion with respect to BA under the same reaction conditions. Out of all the prepared latexes some are suitable for binder purposes in environment friendly water borne coating applications.

Durable Waterborne Hydrophobic Bio-Epoxy Coating with Improved Anti-Icing and Self-Cleaning Performance

This study reports an environment-friendly waterborne hydrophobic bioepoxy coating (WHBC), prepared by introducing dual-scale SiO2 nanoparticles and (3-glycidyloxypropyl) trimethoxysilane into an a...

A waterborne polyurethane coating functionalized by isobornyl with enhanced antibacterial adhesion and hydrophobic property

We report a novel environmental friendly waterborne polyurethane (WPU) coating with good anti-bacterial adhesion property and hydrophobicity. A key point of our approach is to functionize the polyurethane with isobornyl acrylate (IBA), a widely used natural material with unique chiral feature and good biocompatibility. The polyurethanes containing IBA have been synthesized by thiol-ene Michael addition reaction and poly-addition polymerization. The thiol monomer 3-mercapto-1,2-propanediol (TPG) and vinyl monomer isobornyl acrylate (IBA) have been used to obtain dihydroxy-terminated IBA (IBA(OH)2) with triethylamine as catalyst. The structure of IBA(OH)2 have been identified by Fourier transform infrared spectrum (FTIR), proton nuclear magnetic resonance (1H NMR), and mass spectrometry (MS). IBA(OH)2 is then incorporated into polyurethane as a chain extender to yield a WPU with IBA side group (IWPU). The synthesized IWPU has been confirmed by FTIR, 1H NMR, X-ray photoelectron spectroscopy (XPS), and gel permeation chromatography (GPC). Thermogravimetric Analysis (TGA) measurements indicate that the thermal stability of IWPU is decreased slightly with the increasing content of IBA(OH)2. Differential scanning calorimetry further (DSC) indicate that the Tg of the IWPU coatings decreases, and the resistance to low temperature increases at a higher content of IBA(OH)2.The introduction of IBA side groups can improve the hydrophobicity of the polyurethane, which is favorable for wide application of the coatings. Additionally, the antibacterial adhesion performance of the polyurethanes has been evaluated by plate count method and optical density (OD) test. The results demonstrate that the polyurethane coatings with 25 wt% content of IBA side groups can exhibit effective resistance to bacterial adhesion, with the inhibition ratios of 89.3% and 80.4% for E. coli and S. aureus, respectively.

Anticorrosive durability of zinc-based waterborne coatings enhanced by highly dispersed and conductive polyaniline/graphene oxide composite

We developed a novel environment-friendly waterborne zinc-based coating (ZWC) with good corrosion resistance to reduce the environmental hazards caused by solvent-based coatings by introducing a polyaniline-graphene oxide (PAGO) composite into ZWC. The PAGO composite was prepared by in situ polymerization of aniline in the graphene oxide (GO) suspension. Polyaniline (PANI) was evenly distributed in the GO lamellas, which would benefit the uniform dispersion of PANI in aqueous solution. The anticorrosive performance of PAGO-ZWC was analysed and compared with that of pure ZWC, PANI modified Zinc-based waterborne coatings (PANI-ZWC) and GO modified Zinc-based waterborne coatings (GO-ZWC). PAGO could enhance the conductivity of water-based resin, and then facilitated the zinc powder to be linked with the conductive network. The cathodic protection and barrier performance of ZWC were significantly improved by introducing a small amount of PAGO (0.5 wt.% PAGO) into the Zinc-based waterborne resin compared with that of the PANI- ZWC and GO-ZWC, leading to the most effective corrosive resistant of PAGO. The excellent anticorrosion durability was due to the superior dispersibility, high conductivity and good barrier property of PAGO that blocked H2O, O2 and electrolytes from penetrating to the steel substrate.

Aqueous dispersion of polyurethane nanocomposites based on calix[4]arenes modified graphene oxide nanosheets: Preparation, characterization, and anti-corrosion properties

Environmental-friendly waterborne polyurethane/graphene oxides nanocomposites (WPU/GOs) were prepared using p-tert-butyl calix[4]arene (BC4A) and sodium p-sulfonatocalix[4]arene (SC4A) modified GO nanosheets (CGO and SGO) as novel anti-corrosion coatings. Structural, thermal, and morphological investigation of nanosheets by FTIR, XRD, Raman, XPS, TGA, and SEM analysis confirmed their synthesis successfully. Moreover, different properties of WPU/GOs films were also evaluated by ATR-FTIR, XRD, SEM, contact angle, TGA, DSC and tensile analysis. It was found that the modification of GO nanosheets with BC4A and SC4A macrocycles not only overcome the flocculation and coagulation problem of unmodified GO incorporated WPU dispersion (WPU/GO) but also afford better mechanical properties to nanocomposites. The SEM morphological inspection exhibited that the microphase separation degree and dispersion quality of nanosheets within the nanocomposites strongly depends on the type of incorporated nanosheets. Regarding WPU/CGO and WPU/SGO nanocomposites, CGO and SGO nanosheets provide the enhanced storage stability and dispersibility compared to unmodified GO in WPU/GO sample. Anti-corrosion efficiency of the samples was also evaluated by PDS and EIS techniques and the results revealed that the WPU/CGO sample acts as a highly efficient anti-corrosion coating for mild steel and can be introduced as green corrosion protective coating with inhibition efficiency of 99.8%.

Natural rubber particle modified fabrics with catalytic activity and hydrophobicity

We report a novel and facile approach to fabricate functional fabrics using environment-friendly waterborne natural rubber latex (NRL) containing in-situ synthesized gold nanoparticles (AuNPs). AuNPs were prepared and decorated on the surface of the natural rubber particles (NRPs) by heating, forming a dual-scale hierarchical architecture. The hybrid particles of NRPs and AuNPs (AuNP@NRP) were coated on cotton and hydrophilic polyester fabric surfaces, endowing the fabrics with catalytic and hydrophobic features. The treated fabrics with low loadings of AuNP@NRP exhibited high catalytic activity for the reduction of 4-nitrophenol (4-NP) by NaBH4 and could be reused, after easy separation from the catalytic reaction system, with excellent durability. In addition, the hydrophobicity of fabrics increased as coating cycles increased. The obtained hydrophobic fabrics were used for oil/water separation, showing high separation efficiency (>96%).

Polyethylene glycol-based waterborne polyurethane as solid polymer electrolyte for all-solid-state lithium ion batteries

An environmental friendly waterborne polyurethane (WPU) dispersion was synthesized from polyethylene glycol (PEG), hexamethylene diisocyanate (HDI), diethylene glycol (DEG) and dimethylol propionic acid (DMPA). Solid polymer electrolytes based on WPU and LiTFSI were fabricated via an organic solvent free process. The LiTFSI salts were found to be dissolved in WPU by the coordination of Li+ ion with carbonyl and ether group in WPU. The as-prepared WPU showed a semi-crystalline structure and became amorphous after adding lithium salts. The ionic conductivities increased with the increase of salt concentration and followed the Arrhenius behavior. The 20 wt% LiTFSI in WPU electrolyte showed a superior comprehensive performance with an ionic conductivity of 7.3 × 10−4 and 2.2 × 10−3 S cm−1 at 60 °C and 80 °C. All-solid-state LiFePO4/SPE/Li cell using this electrolyte exhibited an initial discharge capacity of 151 mAh g−1 at 0.1C under 60 °C. All of these results demonstrate that this new WPU-based solid polymer electrolyte is a promising environmentally friendly candidate for all-solid-state lithium ion batteries.

Nanocomposites made from thermoplastic waterborne polyurethane and colloidal silica. The influence of nanosilica type and amount on the functional properties

Abstract Novel waterborne polyurethane/silica nanocomposites were prepared via blending of two aqueous dispersions. Polyurethane water dispersion (PUD) was synthesized from polycarbonate diol (PC), 1,6-diisocyanatohexane (HDI) and butane-1,4-diol (BD) in order to provide solely linear character of PU chain. Two types of commercial colloidal silica, Ludox AS and Ludox TMA, differing in the size, shape and type of counter ions were used. The nanocomposites were made from negatively charged PUD and aqueous nanofiller sol at concentrations 5, 32 and 50 wt% of nanosilica. The films were obtained after slow drying of the water mixtures and characterized by AFM, SEM, tensile testing, DMTA, TG and water uptake measurements. It was found that all films are thermoplastics materials, reinforced by hydrogen bonds between silica particles and the polymer matrix, soluble in organic solvents and possible to re-production of PUD. Ludox AS was smaller than TMA and revealed better improvement of PUD-based films due to higher physical cross-linking density. It was observed that film containing 32 wt% of silica Ludox AS showed ten-times increasing Young’s modulus with slight improvement of elongation at break and two-times higher melting temperature in comparison to the neat PU matrix. Moreover sample with 5 wt% of AS nanofiller loading revealed excellent water resistance (swelling 0.8%). The obtained PU/silica nanocomposites have promising applications in recyclable environment-friendly waterborne coatings.

Preparation and Antibacterial Property of Waterborne Polyurethane/Zn–Al Layered Double Hydroxides/ZnO Nanocomposites

In this work, a novel environmental-friendly waterborne polyurethane/ZnAl-layered double hydroxides/ZnO nanoparticles composite (WPU/ZnAl-LDHs/ZnO) was synthesized via in-situ polymerization. ZnAl-LDHs and ZnAl-LDHs/ZnO were synthesized by refluxing in an oil bath. In order to disperse ZnAl-LDHs/ZnO homogeneously into WPU matrix, ZnAl-LDHs/ZnO was firstly functionalized by isophorone diisocyanate. The incorporated content of ZnAl-LDHs/ZnO in the composite has profound effect on such physical properties as mechanical strength, thermal stability and water swelling. It is demonstrated that appropriate amount of ZnAl-LDHs/ZnO with good dispersion in the WPU matrix significantly improves the physical performance of the composites. Finally, the antibacterial activity of the composite was tested against G(-) Escherichia coli and G(+) Staphylococcus aureus. The results indicate that WPU incorporated with ZnAl-LDHs/ZnO shows strong antibacterial activity upon contact.

Waterborne vegetable oil epoxy coatings: Preparation and characterization

The utilization of renewable resources such as vegetable oils [VO] for the development of environment friendly waterborne [WB] materials is encouraged worldwide. The preparation of WB materials from VO is a challenging task due to their hydrophobic nature. The present work describes the synthesis of WB epoxy from VO [WBOE]. WBOE was characterized for its structural and physico-chemical attributes. The cured material was subjected to physico-mechanical, chemical resistance tests, and thermal analyses. The coatings of WBOE showed good physico-mechanical, chemical resistance as well as thermal stability and may find application as eco-friendly WB coatings with safe usage up to 220°C.