Waterborne Polyurethane Dispersions Research Articles

Preparation and Properties of Biobased, Cationic, Waterborne Polyurethanes Dispersions from Castor Oil and Poly (Caprolactone) Diol

Biobased cationic waterborne polyurethanes (WPUs) were prepared using isophorone diisocyanate (IPDI), N-methyl diethanolamine (N-MDEA), polycaprolactone (PCL) diol, hydrochlotic acid (HCl), and 1,4-butanediol (BDO). To improve the mechanical performance and adhesive strength of the waterborne polyurethane films, different amounts of castor oil (CO) acting as a cross-linking agent were incorporated in the polyurethane structure. The structures of the waterborne polyurethanes were assessed by Fourier-transform infrared spectroscopy (FTIR). The combination of CO had a positive effect on the dispersion and stability properties of WPUs. WPUs containing higher content of CO demonstrated a remarkable enhancement in homogeneity among particles. The stable aqueous dispersion was obtained even when N-MDEA loading was as low as 3.2 wt%; a bonus of this low hydrophilic moiety was the excellent adhesive strength, whose T-peel strength could reach up to 36.8 N/25 mm, about 114% higher than that of WPU (17.2 N/25 mm) without any CO content. The elongation at break of CO7.40%-WPU was 391%. In addition, the fracture mechanism of the waterborne polyurethane films transformed from the brittle failure to the ductile fracture. The experiment results showed the CO-modified WPUs displayed excellent film-forming property, flexibility, and adhesion, which can be employed for constructing the eco-friendly, biodegradable, cationic, waterborne polyurethanes.

Castor oil-glycerol-based waterborne polyurethane dispersions

In this study, the castor oil-glycerol-based waterborne polyurethane was successfully synthesized. The molar ratio (the ratio between Gly and total polyols) of Gly was up to 50 % and the effects of Gly on the particle size, stability of dispersion, thermal and mechanical properties, surface wettability of the resulting WPU also has been extensively investigated. Notably, the introduction of Gly has extensively improved the tensile strength, Tg, toughness, Young’s modulus, and pencil hardness. The tensile strength could reach up to 30 MPa and Young’s modulus to 333 MPa with elongation at break over 26 %, Tg to 82 °C, pencil hardness to 6H. However, the surface wettability and ve of the resulting materials increases firstly and then decreases, and exhibit maximum water contact angle of 86.8° for 30 % Gly and maximum ve of 389 mol/m3 for 40 % Gly. This work demonstrates that the introduction of Gly not only can increase the bio-content but also effectively improve the performances of WPU, and this work provides an interesting idea for the preparation of high-performance bio-based WPU.

Bio-based polyurethane aqueous dispersions

Abstract With the advances of green chemistry and nanoscience, the synthesis of green, homogenous bio-based waterborne polyurethane (WPU) dispersions with high performance have gained great attention. The presented chapter deals with the recent synthesis of waterborne polyurethane with the biomass, especially the vegetable oils including castor oil, soybean oil, sunflower oil, linseed oil, jatropha oil, and palm oil, etc. Meanwhile, the other biomasses, such as cellulose, starch, lignin, chitosan, etc., have also been illustrated with the significant application in preparing polyurethane dispersions. The idea was to highlight the main vegetable oil-based polyols, and the isocyanate, diols as chain extenders, which have supplied a class of raw materials in WPU. The conversion of biomasses into active chemical agents, which can be used in synthesis of WPU, has been discussed in detail. The main mechanisms and methods are also presented. It is suggested that the epoxide ring opening method is still the main route to transform vegetable oils to polyols. Furthermore, the nonisocyanate WPU may be one of the main trends for development of WPU using biomasses, especially the abundant vegetable oils.

Polyurethane Impregnation for Improving the Mechanical and the Water Resistance of Polypropylene-Based Textiles.

Commercial waterborne polyurethane (PU) dispersions, different in chemistry and selected on the basis of eco-friendly components, have been applied to a common polypropylene (PP)-based woven fabric. Impregnation has been chosen as a textile treatment for improving the features of basic technical textiles in light of potential applicability in luggage and bag production. The effect of drying method, performed under conditions achieved by varying the process temperature and pressure, on the features of the treated textiles, has been verified. The prepared specimens were characterized in terms of mechanical behavior (tensile, tear and abrasion resistance) and water resistance (surface wettability and hydrostatic pressure throughout the treated textiles). The experimental results suggest an incremental improvement of the tensile features for all the investigated specimens. For tear strength, no augmentation compared to that of the neat textile, could be verified as a consequence of polyurethane treatment. Remarkable improvements of abrasion resistance were displayed for all the impregnated PP textiles. Benefits in water resistance could be attributed to the presence of hydrophobic PU in the textile weaving of the PP samples. The ultimate improvement in water resistance was dependent on drying conditions.

Development of flame-retardant waterborne polyurethane dispersions (WPUDs) from sulfonated phosphorus-based reactive water-dispersible agents

The current study presents an attempt to develop two molecules, namely sulfonated aromatic diol (SAD) and sulfonated aromatic diamine (SADAM), to induce flame retardancy, thermal stability, and dispersion ability for water-based polyurethane dispersions (WPUDs). The previously reported itaconic acid-based polyester polyol was used for prepolymer synthesis as well as for chain extension. Pre- and post-sulfonated compounds were subjected to characterization tests such as FTIR, 13C-NMR, 1H-NMR, and CHNS for confirmation of their structures. The standard dispersant used for the basis of comparison was commercially available dimethyl propionic acid (DMPA). WPUDs were synthesized in different molar concentrations of DMPA, SAD, and SADAM, and the covalent incorporation of all three molecules in the polymer backbone was confirmed by FTIR. The WPUD films were subjected to various thermal tests like TGA and DSC as well as mechanical tests like flexibility and pencil hardness. WPUD films obtained from SADAM showed a remarkable increase in Tg as well as char content. The THRI values for SAD- and SADAM-based films were better than DMPA-based films. SAD- and SADAM-based WPUD films also showed an increase in LOI value and UL-94 ratings with the maximum LOI value of 26. Dispersions based on DMPA showed better stability as compared to dispersions based on SAD and SADAM.

Chemical and Thermo-Mechanical Properties of Waterborne Polyurethane Dispersion Derived from Jatropha Oil.

Nowadays, there is a significant trend away from solvent-based polyurethane systems towards waterborne polyurethane dispersions due to government regulations requiring manufacturers to lower total volatile organic compounds, as well as consumer preference for more environmentally friendly products. In this work, a renewable vegetable oil-based polyol derived from jatropha oil was polymerized with isophorone diisocyanate and dimethylol propionic acid to produce anionic waterborne polyurethane dispersion. Free standing films with up to 62 wt.% bio-based content were successfully produced after evaporation of water from the jatropha oil-based waterborne polyurethane (JPU) dispersion, which indicated good film formation. The chemical and thermo-mechanical properties of the JPU films were characterized. By increasing the OH numbers of polyol from 161 mgKOH/g to 217 mgKOH/g, the crosslinking density of the JPU was significantly increased, which lead to a better storage modulus and improved hydrophobicity. Overall, JPU produced from polyol having OH number of 217 mgKOH/g appears to be a promising product for application as a binder for wood and decorative coatings.

Flame Retardant Modified Bio‐Based Waterborne Polyurethane Dispersions Derived from Castor Oil and Soy Polyol

AbstractAlthough tremendous efforts have been dedicated to developing environmentally friendly bio‐based waterborne polyurethane (WPU) dispersions from vegetable oil, the fabrication of WPU dispersions solely derived from vegetable oil‐based polyol with excellent comprehensive properties is still challenging. In the present work, novel bio‐based WPU dispersions derived from castor oil and soy polyol is successfully modified by phosphorus‐nitrogen chain extender [bis(2‐hydroxyethyl)amino]‐methyl‐phosphonic acid dimethyl ester (BH). The structure and properties of the dispersions and films are characterized systematically by Fourier transform infrared spectroscopy, thermogravimetric analysis , mechanical test, and limiting oxygen index (LOI), etc. The results indicate that bio‐based WPU films display moderate mechanical performance by adjusting BH content, and the WPU film containing 100% BH with 47.8% biobased content has a tensile strength of 8 MPa and the highest Young's modulus of 62.3 MPa. The incorporation of BH can increase the production of char residue. The flame retardancy of WPU films increase gradually with the BH molar content, and the LOI value of the WPU100 with 1.53 wt% phosphorus content can reach as high as 28.1%. This work may provide a new approach to develop high biobased content, eco‐friendly, flame retardant WPU for application in the surface coating industry.

Waterborne Polyurethane Dispersions and Thin Films: Biodegradation and Antimicrobial Behaviors.

Biodegradable and antimicrobial waterborne polyurethane dispersions (PUDs) and their casted solid films have recently emerged as important alternatives to their solvent-based and non-biodegradable counterparts for various applications due to their versatility, health, and environmental friendliness. The nanoscale morphology of the PUDs, dispersion stability, and the thermomechanical properties of the solid films obtained from the solvent cast process are strongly dependent on several important parameters, such as the preparation method, polyols, diisocyanates, solid content, chain extension, and temperature. The biodegradability, biocompatibility, antimicrobial properties and biomedical applications can be tailored based on the nature of the polyols, polarity, as well as structure and concentration of the internal surfactants (anionic or cationic). This review article provides an important quantitative experimental basis and structure evolution for the development and synthesis of biodegradable waterborne PUDs and their solid films, with prescribed macromolecular properties and new functions, with the aim of understanding the relationships between polymer structure, properties, and performance. The review article will also summarize the important variables that control the thermomechanical properties and biodegradation kinetics, as well as antimicrobial and biocompatibility behaviors of aqueous PUDs and their films, for certain industrial and biomedical applications.

Antiglare waterborne polyurethane/modified silica nanocomposite with balanced comprehensive properties

To endow antiglare waterborne polyurethane with toughness, thermal stability, and water resistance is highly desired. Herein, we first prepared amphiphilic polyurethane modified silica (MSiO2) nano-particles by in-situ polymerization and then physically incorporated it with waterborne polyurethane (WPU) dispersion to fabricate WPU composite (WPU-MSiO2). The FT-IR, TG-DTG, and SEM analyses demonstrated that the urethane chains were covalently attached onto the silica surface, and the MSiO2 exhibited good dispersibility and compatibility with WPU matrix. Moreover, embedded MSiO2 particles could not only impart the WPU-MSiO2 composites with good antiglare function, but also improve the mechanical, thermal, and water resistance of composites. Notably, the most effective enhancements in antiglare and other physicochemical performances were achieved when incorporating 3 wt% of MSiO2 into the WPU dispersion to fabricate the WPU-MSiO23 composite. In particular, the WPU-MSiO23 composite film possessed the transmittance of 94.6% and 60° gloss of 27.0, respectively, which satisfying the requirement of an antiglare coating. Furthermore, WPU-MSiO23 composite exhibited great increase in tensile strength, elongation at break, maximum decomposition temperature, and water contact angle (20.8 MPa, 636.5%, 389.5 °C, and 99.1°, respectively) as well when compared to the neat WPU and WPU-SiO23 films. The present research provided a cost-effective way for preparing high-performance antiglare polymer coatings.

Correction to: Development of waterborne polyurethane dispersions (WPUDs) from novel cardanol‑based reactive dispersing agent

The authors declare that for any communication of this article, the corresponding author should be considered as Prof. (Dr.) S. T. Mhaske (stmhaske@gmail.com).

Practical two‐step chain extension method to prepare sulfonated waterborne polyurethanes based on aliphatic diamine sulphonate

AbstractWe reported a novel synthesis route to fabricate sulfonated aliphatic waterborne polyurethane dispersions (SWPU) only based on 2‐[(2‐aminoethyl) amino] ethane sulphonate sodium (AAS‐Na) by two‐step chain extension method with the assistance of acetone and water cosolvent. When AAS‐Na was added, only less than 50% of AAS‐Na was incorporated into polyurethane chain in the first‐step chain extension and the residual AAS‐Na formed molecular aggregates which were insoluble in acetone due to the high polarity of AAS‐Na. Subsequently, the mixture of acetone and water was added, the residual AAS‐Na aggregates dissolved, undertaking the further second‐step chain extension reaction, and the ultimate reaction conversion of AAS‐Na rose to more than 90%. The mechanism for acetone and water cosolvent to affect the preparation of SWPU dispersions was studied, as well as the water resistance, mechanical properties and hydrolysis resistance of as‐prepared SWPU dispersions. With the decrease of AAS‐Na content from 2.0% to 1.2%, the peak area of the melting peaks for SWPU films increased, as well as the water resistance. And the as‐prepared polyester SWPU exhibited good hydrolytic stability.

Synergistic enhancement of UV-resistance and electrical conductivity of waterborne polyurethane composite with combination of functionalized 2D graphene oxide and 1D nanocellulose

In this work, a functionalized graphene oxide@functionalized nanocellulose (FGO@FNC) composite filler, that was firstly synthesized by using isocyanatopropyltriethoxysilane (IPTS) as a coupling agent through a sol-gel process, and subsequently incorporated into waterborne polyurethane (WPU) dispersion via a simple and scalable solution blending method to prepare WPU composite (WPU/FGO@FNC). It was found that for the as-prepared FGO@FNC filler, the urethane chains were covalently grafted onto the surface of 2D graphene oxide and 1D nanocellulose, as well as siloxane linkages were formed between FGO and FNC as a result of co-condensation. Notably, the inserted FGO@FNC filler, dispersing excellently within the WPU matrix, could reinforce mechanical properties, improve surface hydrophobicity and electrical conductivity of WPU/FGO@FNCs composites, and particularly enhance the UV-resistant performance. Furthermore, the most effective enhancement was acquired when 3 wt% of FGO@FNC was incorporated into the WPU matrix, i.e., the WPU/FGO@FNC3 composite, that showed surpassing mechanical properties (σb = 28.7 MPa, εb = 462.8 %), water contact angle (96.5°), and electrical conductivity (0.252 S/m); and more importantly, it retained considerably in physicochemical parameters nearly above 78 % after five days of UV exposure. This work offers a viable avenue for developing UV-resistant, electrical conductive, tough and hydrophobic multi-functional coatings.

UV absorption, anticorrosion, and long-term antibacterial performance of vegetable oil based cationic waterborne polyurethanes enabled by amino acids

This study provides a simple method for tailoring the performance of the WPUs by employing amino acids as environmentally-friendly proton sources, which eliminates long-standing issues of WPUs, such as irritating odor, corrosiveness, and air pollution. • Novel WPU have been successfully prepared using amino acids as proton sources. • WPU ranging from flexible elastomers to tough plastics can be tailored by acids. • Tunability of hydrogen bonding confers UV protection and anti-bacterial to WPU. • Application of amino acid eliminates irritating odor, corrosiveness issues of WPU. Acids are traditionally used in the production of environmentally-friendly cationic waterborne polyurethane dispersions. However, the effect of their conjugate bases on the final properties of waterborne polyurethanes has been rarely explored. In this study, the effect of different acids in tailoring the performance of bio-based cationic waterborne polyurethanes has been reported. Polyurethane films ranging from flexible elastomers to tough plastics can be obtained, and their properties can be simply controlled by the selection of the acids. The tunability of the hydrogen bonding strength confers the resulting polyurethane films enhanced multi-function, such as UV absorption, anticorrosion properties, and long-term antibacterial performance. These results represent a significant advancement over traditional techniques, providing a simple strategy to tailor the performance of cationic waterborne polyurethanes, and offering environmentally-friendly amino acid substitutes for commonly used acids, such as acetic acid, HCl, or glycolic acid. The methodology described here eliminates long-standing issues of PUs, such as irritating odor, corrosiveness, and air pollution.

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.

Development of waterborne polyurethane dispersions (WPUDs) from novel cardanol-based reactive dispersing agent

The objective of the current research work is to prepare a difunctional reactive dispersing agent derived from cardanol which can be used as an alternative for dimethylol propionic acid (DMPA) in waterborne polyurethane dispersion synthesis. The novelty of the research lies between the use of bio-based resource and utilizing the sulfonic acid group as an anionic dispersible group. The cardanol was sulfonated using oleum followed by the reaction of the hydroxyl group of phenol with the epichlorohydrin (ECH). The obtained product was then hydrolyzed to generate double functionalities which can be introduced in the PU backbone through a chemical reaction with a diisocyanate. The obtained intermediates and product were characterized using hydroxyl values, epoxy equivalent weights (EEW), CHNS analysis, FTIR and 1H-NMR analysis. The typical acetone process was used for the preparation of WPUDs, and the cured films were further analyzed for the various coating properties in which thermal properties showed significant improvements with the incorporation of HESC to the PU system along with the increased char yield and glass transition temperature (Tg), whereas the mechanical properties did not show any improvements, which could be attributed to the bulky structure of HESC and increased rigidity in the polymeric network. The detailed synthesis, characterizations and obtained results are presented and discussed here.

In situ preparation and properties of waterborne polyurethane/edge-isocyanated hexagonal boron nitride composite dispersions

In this study, a series of waterborne polyurethane (WPU) dispersions were prepared by in situ polymerization of edge-isocyanated hexagonal boron nitride (hBN-NCO) nanosheets suspension. The hBN-NCO nanosheets act as both cross linkers and nano-fillers in the composites, and meanwhile, the interfacial compatibility and dispersion of the inorganic nano-fillers in polymer substrates were also greatly improved. Therefore, the WPU films containing only 2 wt% hBN-NCO nanosheets exhibited remarkable mechanical strength and favorable wear resistance, and its stress and Young’s modulus increased by threefold and tenfold, respectively, as compared to those of pure WPU film. Moreover, its low corrosion current density (2.5 × 10−9 A cm−2) and high corrosion potential (0.79 V) enhanced the corrosion resistance of the WPU coating.

Synthesis and properties of self-crosslinking waterborne polyurethane with side chain for water-based varnish

In this paper, a series of self-crosslinking waterborne polyurethane (WPU) dispersions with side chain, which is (3-(2-Aminoethyl)aminopropyl)trimethoxysilane (AEAPTMS) as the diamine chain extender, were prepared. The characteristics of WPU with different dosages of AEAPTMS were evaluated, including particle size, crystallinity, surface performance, water resistance and thermal stability. It was demonstrated that AEAPTMS was successfully incorporated into the WPU from Fourier-transform infrared spectroscopy (FT-IR). Once the content of AEAPTMS increased to 5 %, the WPU dispersions became gelatinous. That is, the siloxane groups were hydrolyzed into a cross-linked structure during the emulsification process. The particle size enlarged with the increasing dosage of AEAPTMS in transmission electron microscopy (TEM). The X-ray photoelectron spectroscopy showed that the silane in the cross-linked WPU migrated freely towards the WPU film surface. The addition of AEAPTMS enhanced the tensile strength, hydrophobicity, water resistance and thermal stability of WPU film. Meanwhile, the elongation at break and crystallinity of WPU films were declined. Besides, interestingly, the glass transition temperature of WPU films followed the trend of first rising and then falling. By adding wetting agent, antifoaming agent, adhesion promoter and flatting agent into WPU, the water-based varnish was prepared. The pencil hardness, water resistance, adhesion and anti-adhesion of water-based varnish were best in the application on the stainless steel substrate when the WPU sample was Si-WPU-3.

Preparation and characterization of modified castor oil via photo‐click chemistry forUV‐curable waterborne polyurethane with enhanced water resistance and low conductive percolation threshold

AbstractA 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.

UV‐shielding by a polyurethane/f‐Oil fly ash‐CeO2 protective coating

AbstractA waste material called oil fly ash (OFA) was acid‐functionalized, yielding f‐OFA‐COOH, which was then reacted with cerium oxide (CeO2) to make CeO2‐functionalized OFA, or f‐OFA‐CeO2. Pristine OFA and f‐OFA‐CeO2 were used to make waterborne polyurethane (WBPU) dispersions, referred to as WBPU/OFA and WBPU/f‐OFA‐CeO2, respectively, with defined OFA and f‐OFA‐CeO2 content. All the dispersions were applied to mild steel as organic coatings to evaluate their protective properties, such as their hydrophobicity, adhesive strength and UV‐shielding resistance. These protective properties varied based on the OFA and f‐OFA‐CeO2 content. The highest water contact angle, minimum water swelling and maximum adhesive strength were found using WBPU/f‐OFA‐CeO2‐20 coating (using 2.00 wt% f‐OFA‐CeO2), which also showed the maximum ultraviolet (UV) absorption via UV–vis spectroscopy analysis. This UV shielding result also matched field test results, as that coating was found to exhibit the lowest UV degradation near a marine atmosphere, as shown by X‐ray photoelectron spectroscopy (XPS) analysis. The least affected hydrophobicity was also recorded for the sample with the WBPU/f‐OFA‐CeO2‐20 coating.

Eco-Friendly Castor Oil-Based Delivery System with Sustained Pesticide Release and Enhanced Retention

The deposition of pesticides and their retention on plant surfaces are critical challenges for modern precision agriculture, which directly affect phytosanitary treatment, bioavailability, efficacy, and the loss of pesticides. Herein, a novel and eco-friendly waterborne polyurethane delivery system was developed to enhance the spray deposition and pesticide retention on plant surfaces. More specifically, biobased cationic and anionic waterborne polyurethane dispersions were synthesized from castor oil. Both cationic and anionic polyurethane dispersions exhibited remarkable microstructural, amphiphilic, and nanoparticle morphologies with a core-shell structure that served to encapsulate a biopesticide (azadirachtin) in their hydrophobic cores (WPU-ACT). The results indicated that the cationic WPU-ACT carriers exhibited a better sustained release behavior and a better protective effect from light and heat for azadirachtin. In addition, the simultaneous spray of anionic and cationic WPU-ACT significantly enhanced the spray deposition and prolonged the retention of pesticides due to the reduced surface tension and surface precipitation induced by the electrostatic interaction when two droplets with opposite charges come into contact with each other. A field efficacy assessment also indicated that the simultaneous spray of anionic and cationic WPU-ACT could control the infestation of brown planthopper in rice crops. Castor oil-based waterborne polyurethanes in this study work as an efficient pesticide delivery system by exhibiting enhanced deposition, rainfastness, retention ability, protection, and sustained release behavior, holding great promise for spraying pesticide formulations in modern and environmentally friendly agricultural applications.