Waterborne Polyurethane Dispersions Research Articles

Preparation and characterization of hydrophobic waterborne polyurethane self‐matting coating

AbstractA green method to synthesize self‐matting waterborne polyurethane acrylic hybrid emulsion with hydrophobic function is introduced in this study. A reactive waterborne polyurethane (RWPU) dispersion containing unsaturated CC double bonds was prepared from epoxidized soybean oil. Subsequently, the RWPU dispersion was copolymerized with fluorinated monomers of different carbon chain lengths to prepare polyurethane acrylic hybrid emulsion (PUF). The results revealed the gloss levels of PUF films to be as low as 12.4 gloss units at 60°. The morphology of PUF films was observed by scanning electron microscope and three‐dimensional surface profilometer, and the relationship between surface roughness and gloss was discussed in detail. In addition, thermal gravimetric analysis was conducted to determine the thermal stability of the PUF films, and the results denoted that these PUF films exhibited excellent thermal stability. Comprehensive performance tests indicated that the RWPU dispersion, which was copolymerized with hexafluorobutyl methacrylate at a weight of 10%, exhibited a low gloss, a high contact angle of 120°, and a high elongation percentage of 423%. Furthermore, the dynamic light scattering results showed small average particle size, revealing the excellent storage stabilities.

Preparation and coating properties of alkyd polyol-based autoxidizable waterborne polyurethane dispersions with high fatty acid content, long storage stability, and low viscosity

Preparation and coating properties of alkyd polyol-based autoxidizable waterborne polyurethane dispersions with high fatty acid content, long storage stability, and low viscosity

Novel multifunctional highly crosslinked bio-based waterborne polyurethane networks modified via long fatty hydrophobic side chains

The mechanical properties and water resistance of castor oil-based waterborne polyurethane are mutually limited due to the presence of a hydrophilic chain extender. Herein, Arbutin (AT) was used as a crosslinking agent, and benzimidazole (CR-455) was utilized as an ultraviolet absorber, sustainable long fatty hydrophobic chain extenders, sorbitan monooleate (SP), glycerol laurate (GML), glycerin monostearate (GMS), and trimethylolpropane monooleate (TPM), were introduced into castor oil-based waterborne polyurethane (CWPU) backbones through molecular structure design respectively. Subsequently, the amount of SP was changed to prepare a series of waterborne polyurethane dispersions, and their emulsion and film properties were thoroughly investigated. The finding showed that the incorporation of long fatty hydrophobic chain extenders led to an increase in crosslinking density, thereby endowing CWPU films with good mechanical properties, water resistance, and anti-corrosion efficacy. Moreover, the bio-based content in the CWPU film had reached an impressive 90.9 %. The addition of SP content resulted in a gradual improvement in the mechanical properties, water resistance, and corrosion resistance of CWPU-SP films. When the SP content was 40 %, due to the high strength of hydrogen bonds and the density of crosslinking in systems, the tensile strength, toughness, water absorption rate, and corrosion protection efficiency of the CWPU-SP40 film reached 18.1 MPa, 20 MJ/m3,7.7 %, and 98.47 %, respectively. Particularly, the prepared transparent CWPU films exhibited complete UV shielding. This work would pave the way for the application of bio-based waterborne polyurethanes in high-performance coatings, such as anti-corrosion and sunscreen.

High solid content waterborne polyurethane with high foaming rate to artificial leather: Synthesis and characterization

A type of high solid content waterborne polyurethane (HSWPU) dispersions applied to foamed artificial leathers were designed and prepared by prepolymer method. The solid content of the waterborne polyurethane dispersions could reach 53 %, and the foaming ratio could reach an astonishing 2.50 by adjusting the parameters. The influence of synthesis parameters, including R value (molar ratio of -NCO/-OH), D value (hydrophilic group content), trimethylol propane (TMP) content (degree of crosslinking) and ethylenediamine (EDA) content (it was chain extender) on foaming ratio were investigated. Meanwhile, a series of properties of HSWPU dispersions, films and foamed artificial leathers were introduced in detail. The results demonstrated that R value, TMP content, D value and EDA content synergistically decided the foaming properties of HSWPU dispersions in three aspects: three-dimensional structure, surface tension and polarity, respectively. With optimized parameters of R = 2.0, TMP = 0.4 wt%, DMPA = 3.0 wt% and EDA = 60 wt%, the HSWPU dispersions had good appearance and stability, and the latex particles exhibited excellent water, acid and alkali resistance after films formation. The HSWPU dispersions with high foaming rate without collapsing in the foam-forming process and created uniformly bubble pores. In terms of application properties, the prepared foamed artificial leathers showed admirable air permeability and water vapor transmissions. All results distinctly demonstrate a feasible yet promising paradigm for applying the HSWPU on foamed artificial leathers had great potential applications.

UV-curable acrylic end-capped amphoteric waterborne polyurethane coatings

Waterborne polyurethane dispersions (WPUs) are environmentally friendly coatings since they present low amount of volatile organic compound amounts (VOCs). In the majority of the WPUs the dispersions are balanced with anionic groups and accordingly their stability at low pH is limited. In order to this drawback to be solved, in this work a tertiary amine containing chain extender (triethanolamine, TEOA) was introduced together with a conventional internal emulsifier (carboxylic acid) in acrylic end-capped polyurethane dispersions giving rise to amphoteric UV curable WPUs. After adding a radical photo-initiator and film formation, the coatings were cured under UV irradiation. The properties of amphoteric and anionic dispersions were compared. The best properties were obtained for the samples containing a 1/1 amine/acid molar ratio. Thus, while the anionic dispersions coagulated at low pH values, the 1/1 amphoteric dispersion showed high stability to pH changes. After curing this sample with UV irradiation, the gel content of the film was higher and the water vapour transmission rate was lower than that of the anionic polyurethane because of the strong acid/base interaction. The results showed that the amphoteric WPUs are promising for various applications, offering stability over a wider pH range than traditional formulations.

Pickering emulsion approach: A novel strategy to fabricate waterborne polyurethane with enhanced abradability and water-resistance comparable to that of solvent-based coating

The urgent requirement of replacement for solvent polyurethane (PU) makes waterborne polyurethane (WPU) coating more attractive and popular in many industrial areas. However, the simultaneous realization of good dispersion stability and high performance of the cured films especially water resistance remains challenging. Herein, we propose a novel and facile Pickering emulsion approach to fabricate WPU with enhanced abradability and water-resistance comparable to that of solvent-based PU coating. In this approach, the hydrophobic polyurethane synthesized by poly-addition reaction in ethyl acetate is directly dispersed into water with SiO2 nanoparticles as Pickering stabilizer followed by subsequent evaporation of the remaining solvent to obtain Pickering waterborne polyurethane dispersion (PWPU dispersion). The ability of SiO2 to stabilize emulsion can be modulated by hydrophobic modification with propyltriethoxysilane (PTS). SiO2 nanoparticles with an optimal PTS-grafting rate of 2.8 wt% enables the PWPU dispersion with excellent long-term, chemical, thermal, and freeze-thaw stability. The highly-transparent composite films with honeycomb structures are readily formed by casting PWPU dispersion at room temperature. The thermal and mechanical properties of PWPU films are comparable to or superior to solvent-borne polyurethane (SPU) and self-emulsifying waterborne polyurethane (SWPU) films. Moreover, the water absorption of the PWPU-5 film is approximately 20 times lower than that of SWPU, demonstrating the excellent water-resistance. We further validated the coating performance of PWPU for leather finishing. The hydrophobicity, abrasion resistance and water vapor permeability of PWPU-coated leather are superior to those of SPU and SWPU-coated leather.

Bio‐based waterborne polyurethane structural color films with high stability

AbstractIn recent years, structural colors derived from photonic crystals (PCs) with a periodically ordered nanostructure are gorgeous and iridescent, but once their structure is destroyed, they will fade. In this work, the feasibility of the application of bio‐based waterborne polyurethanes (WPU) in structural color films was explored. The structural stability of PCs is enhanced bio‐based WPU as a kind of green product, which can replace solvent polyurethane one. A tung oil polyol (TOP) is fabricated by one‐step method with simple purification process and used to prepare waterborne polyurethane dispersions (WPUD). More introduction of TOP into the WPUD may help improve tensile strength and hydrophobic capability. It shows excellent mechanical properties with 16.8 MPa in tensile strength and water contact angle 109.5°. The SEM images confirmed that bio‐based WPU is more conducive to the self‐assembly of silica particles than traditional WPU.

Novel enrichment in biobased monomers of waterborne polyurethane dispersions as a textile finishing agent for poly-cotton fabrics

This study introduces a novel biobased textile finishing agent synthesized as waterborne polyurethane dispersions (FCCB-WPUDs), utilizing bio-based monomers like fenugreek oil-based polyol, corn oil-derived emulsifier, and cellulose acetate butyrate (CAB) chain extender. The FCCB-WPUDs were prepared through the prepolymer polymerization method and characterized using FTIR, TGA, DMA, SEM, DLS, and swelling tests. Their application to poly-cotton fabrics significantly improved various fabric properties. The enhancements included increased washing fastness (from 3/4 ± 0.01 to 4 ± 0.02 for dyed and 3 ± 0.02 to 4/5 ± 0.02 for printed fabrics), rubbing fastness (from 3 ± 0.02 to 4/5 ± 0.03 for dyed and 4 ± 0.02 to 4/5 ± 0.03 for printed fabrics), and perspiration fastness (from 3 ± 0.02 to 4 ± 0.03 for acidic dyed and 3/4 ± 0.02 to 4 ± 0.02 for alkaline printed fabrics). Additionally, tear strengths improved significantly (from 13.66 ± 0.04 N/m to 20.53 ± 0.06 N/m for warp dyed and 10.85 ± 0.06 N/m to 15.14 ± 0.06 N/m for warp printed fabrics), along with tensile strengths (from 327 ± 5.38 N/m to 361 ± 3.26 N/m for warp dyed and 357 ± 5.34 N/m to 449 ± 4.90 N/m for warp printed fabrics). These improvements correlated with increasing CAB moles as a chain extender. This research presents a cost-effective and simple biobased method for textile finishing, offering an alternative to petrochemical-based monomers in conventional WPUD preparation.

Bio-based non-isocyanate polyurethane(urea) waterborne dispersions for water resistant textile coatings

Currently, the resins used in industrial polyurethane coatings are made from petro-based polyols and isocyanate building blocks. In traditional coating formulations, polyurethane resins can be solubilized in solvents for their application on substrates, thus releasing possibly volatile organic compounds (VOCs) upon drying. To circumvent these issues, polyurethanes synthesized from non-isocyanate and bio-based building blocks are receiving more interest. However, only few references describe the development of waterborne non-isocyanate dispersions with a direct application.In this study, non-isocyanate polyurethane(urea)s of very high bio-based contents (>80 wt%) and having controlled amount of reactive hydroxyl ends were synthesized via transcarbamoylation. The obtained resins were used as cationic waterborne dispersions in a sustainable coating system. The influence of the functionality and hydrophobicity of the neutralization agent used to protonate the non-isocyanate polyurethane(urea) backbones, as well as the dicarbamate monomer structures were assessed. It was found that the combination of monofunctional and hydrophilic dl-lactic acid neutralization agent (for electrostatic repulsion) led to stable dispersions with better properties (particle size and zeta potential) than the commercial waterborne polyurethane dispersion reference. Those dispersions were cross-linked through their reactive hydroxyl end groups with tetramethylol acetylene diurea into freestanding films and adhesive layers for textile coatings. The freestanding films exhibited high cross-linking efficiency (gel content >90 %), low water uptake (down to 2 %) and high water and methyl ethyl ketone (MEK) resistance (≥200 rubs) as well as good mechanical properties (Young's modulus between 1.5 MPa and 3.1 MPa and elongation at break up to 300 %) to resist the deformation of the fabrics when applied on them. Finally, when used as an adhesive layer on textiles, good resistance to hydrolysis and heat aging were ensured by the coating system, thus potentially replacing isocyanate based adhesive layers.

Puncture Resistance and UV aging of Nanoparticle-Loaded Waterborne Polyurethane-Coated Polyester Textiles.

The goal of this research was to investigate the effect of different types of nanoparticles on the UV weathering resistance of polyurethane (PU) treatment in polyester-based fabrics. In this regard, zinc oxide nanoparticles (ZnO), hydrophilic silica nanoparticles (SiO2 (200)), hydrophobic silica nanoparticles (SiO2 (R812)), and carbon nanotubes (CNT) were mixed into a waterborne polyurethane dispersion and impregnated into textile samples. The puncturing resistance of the developed specimens was examined before and after UV-accelerated aging. The changes in chemical structure and surface appearance in nanoparticle-containing systems and after UV treatments were documented using microscopic pictures and infrared spectroscopy (in attenuated total reflectance mode). Polyurethane impregnation significantly enhanced the puncturing strength of the neat fabric and reduced the textile's ability to be deformed. However, after UV aging, mechanical performance was reduced both in the neat and PU-impregnated specimens. After UV treatment, the average puncture strength of all nanoparticle-containing systems was always greater than that of aged fabrics impregnated with PU alone. In all cases, infrared spectroscopy revealed some slight differences in the absorbance intensity of characteristic peaks for polyurethane polymer in specimens before and after UV rays, which could be related to probable degradation effects.

Synthesis and characterization of waterborne polyurethane-based ink binder modified via a silane coupling agent

The development of high-performance waterborne polyurethane ink binder presents challenges due to the lack of outstanding water resistance, adhesion, and heat resistance in traditional waterborne polyurethane. Herein, series of waterborne polyurethane emulsions were synthesized using the pre-polymerization chain expansion and self-emulsification method, with varying contents of 3-aminopropyl triethoxysilane as the modified post-chain extender. The effect of varying the concentration of 3-aminopropyl triethoxysilane on the characteristics of waterborne polyurethane dispersions and films was investigated. The results indicated that there was a significant improvement in adhesion, thermal stability, and water resistance with an increase in the concentration of 3-aminopropyl triethoxysilane. Specifically, When the introduction amount was 3 wt%, the resulting film exhibited the best overall properties, including a tensile strength of 48.4 MPa, water absorption of 4.3 wt%, shear strength and adhesion of 3.9 MPa and 3.86 MPa respectively, as well as a T-peel strength of 14.9 N/mm. This work provided meaningful guidance for developing a novel waterborne polyurethane-based ink binder with strong adhesion, high mechanical properties, and excellent water resistance.

Preparation and characterization of high solid content cationic waterborne polyurethane with core‐shell structures

AbstractIn this study, core‐shell structured cationic waterborne polyurethane (WPU) dispersions with high solid content were prepared. To this end, prepolymer A was synthesized from polytetramethylene ether glycol (PTMG), isophorone diisocyanate (IPDI), castor oil (CO) and 1,4‐butanediol (BDO) without integration of the hydrophilic groups. Prepolymer B with hydrophilic groups was prepared from PTMG, IPDI, CO, BDO and N‐methyldiethanol amine (MDEA). WPU dispersion with a core‐shell structure could be generated by mixing, neutralizing, and emulsifying of the prepolymer A and the prepolymer B. The results indicated that the generation of WPU dispersions through this technique exhibited a milky appearance while the pH values range from 5.30 to 5.60. The optimal combination of prepolymer A and prepolymer B (at a ratio of 5:5) resulted in a dispersion with the highest solid content (50.4%), lowest viscosity (69 mPa·s), and narrowest particle size distribution. As the proportion of prepolymer A to prepolymer B decreases, the tensile strength of WPU film reduces while the elongation at break and glass transition temperature increases. Moreover, initially the contact angle with water was decreased instead of increase. However, modifications in a ratio of prepolymer A and B was not showed any significant impact on the thermal stability performance of the WPU films.

Sustainable Strategies for Synthesizing Lignin-Incorporated Bio-Based Waterborne Polyurethane with Tunable Characteristics.

In this study, we introduce a novel approach for synthesizing lignin-incorporated castor-oil-based cationic waterborne polyurethane (CWPU-LX), diverging significantly from conventional waterborne polyurethane dispersion synthesis methods. Our innovative method efficiently reduces the required solvent quantity for CWPU-LX synthesis to approximately 50% of that employed in traditional WBPU experimental procedures. By incorporating lignin into the polyurethane matrix using this efficient and reduced-solvent method, CWPU-LX demonstrates enhanced properties, rendering it a promising material for diverse applications. Dynamic interactions between lignin and polyurethane molecules contribute to improved mechanical properties, enhanced thermal stability, and increased solvent resistance. Dynamic interactions between lignin and polyurethane molecules contribute to improved tensile strength, up to 250% compared to CWPU samples. Furthermore, the inclusion of lignin enhanced thermal stability, showcasing a 4.6% increase in thermal decomposition temperature compared to conventional samples and increased solvent resistance to ethanol. Moreover, CWPU-LX exhibits desirable characteristics such as protection against ultraviolet light and antibacterial properties. These unique properties can be attributed to the presence of the polyphenolic group and the three-dimensional structure of lignin, further highlighting the versatility and potential of this material in various application domains. The integration of lignin, a renewable and abundant resource, into CWPU-LX exemplifies the commitment to environmentally conscious practices and underscores the significance of greener materials in achieving a more sustainable future.

Waterborne polyurethane dispersions based on polypropylene glycol/polycarbonate diol: Evaluation of their use as wood protective coatings

AbstractWhen exposed to the open air, the wood can change its physical and structural properties due to the combined effect of ultraviolet radiation, oxygen, humidity, atmospheric pollutants, and microorganisms. The demand for durable coatings with application to wooden structures or pieces is always a relevant topic. Waterborne polyurethane (WPU) dispersions as wood protective coatings might be attractive, especially outdoors. In this work, WPU dispersions have been synthesized from isophorone diisocyanate and different ratios of polypropylene glycol and polycarbonate (PC) diol. Synthesized polyurethanes were applied to wood surfaces as a coating. The results showed that the partial and total replacement of polypropylene glycol (PPG) by PC influences the mechanical, thermal, and structural properties of the films obtained from aqueous polyurethane dispersions. In addition, a simple and promising methodology based on Fourier‐transform infrared (FTIR) spectra was proposed to determine the polycarbonate content in poly(carbonate‐ether‐urethane). The synthesized coatings reduced water absorption by the wood, especially the one with a 25:75 polycarbonate to PPG ratio. The applied coating does not impact the final color of the wood, allowing a natural aging effect. Polyurethanes are promising for use as coatings for wood.

Emulsion homopolymerization of chlorotrifluoroethylene toward new waterborne fluorocarbon coatings

To solve the problems of environmental unfriendliness brought by long fluoroalkyl chain surfactant used in the homopolymerization of chlorotrifluoroethylene (CTFE) monomers as well as film forming difficulty and poor adhesion of PCTFE resins at the same time, a short fluoroalkyl capping waterborne polyurethane (F-WPU) dispersion was firstly synthesized in this work based on the processes of self-emulsification and phase inversion. The prepared fluorinated polyurethane dispersions could reduce the surface tension of water to 17.81–19.04 mN/m, showing high surface activity. Subsequently, the PCTFE (Poly(chlorotrifluoroethylene)/F-WPU composite latex was successfully prepared by emulsion homopolymerization, of which the F-WPU was used as the stabilizer and microreactor of system to emulsify CTFE monomers and then the corresponding composite coatings were further fabricated. Effects of the type and addition amount of F-WPU on emulsion homopolymerization of CTFE and the stability of composite emulsion were systematically studied. As a result, the PCTFE/F-WPU composite latex exhibits excellent wetting ability on various low surface energy substrates, and the composite coating displayed excellent adhesion and UV (Ultraviolet) resistance due to the synergistic action of F-WPU and PCTFE. The synthesis of F-WPU not only opens up a new route for the preparation of fluorinated surfactants, but also provides a new method for the emulsion homopolymerization of fluoroethylene monomers, and accelerates the wide application of fluorocarbon latex coating.

High solid and low viscosity waterborne polyurethane acrylate with excellent anti-corrosion and anti-bacterial performances

The design and preparation of great corrosion resistance and high-solid waterborne polyurethane dispersion with low viscosity is still a challenge in the field of the polyurethane industry. Herein, we developed a simple method involving a core-shell process to prepare a core-shell structured waterborne polyurethane acrylate dispersion (WPUAD). First, isobornyl acrylate, a derivative of natural product borneol, dihydroxylated by a thiol-ene click reaction was used to prepare oil-based polyurethane acrylate as prepolymer A (core) and waterborne polyurethane acrylate as prepolymer B (shell). Then, the core-shell WPUAD was obtained by mixing and emulsifying the two prepolymer at a certain ratio. The study reveals that the core-shell structured WPUAD not only has a low viscosity (~1330 mPa.s) but also holds a high-solid content (~ 60 wt%). At the same time, the highly solid WPUAD has excellent stability with no breast breakage even after more than 1 year of storage. In addition, various electrochemical measurements, water contact angles, and water absorption tests were performed to determine the anti-corrosive properties of the WPUAD-derived coatings. The results show that the WPUA coatings exhibit significantly enhanced anticorrosion with respect to the single prepolymer B derived coatings, which is attributed to their high cross-linking density resulting from the core-shell structure and the introduction of hydrophobic isobornyl acrylate. In addition, because of the introduction of the dihydroxylated isobornyl acrylate as chain extenders, the WPUA coating has great anti-bacterial adhesion properties with an anti-bacterial efficiency of 82.3 %. We believe that our work provides a generic preparation method to obtain a commercially available high-solid WPUAD with excellent anti-corrosion properties.

Influence of bio-based 2,5-furandicarboxylic acid on the properties of water-borne polyurethane dispersions

Two sets of polyesters derived from 1,6-hexanediol, succinic acid, and varying amounts of a second aromatic dicarboxylic acid have been prepared. In the first set, isophthalic acid has been used as an established rigid building block for these types of materials. In the second set, isophthalic acid was replaced by the bio-based aromatic diacid 2,5-furandicarboxylic acid. The structure and properties of the polyesters have been characterized. All polyesters prepared were subsequently used as polyols for the synthesis of water-borne polyurethane dispersions. Films were prepared from the aqueous dispersions to characterize the performance of the materials. It was observed that the bio-based 2,5-furandicarboxylic acid not only has similar beneficial effects on the thermal and mechanical properties of the polyurethane coatings, but in some cases, like pendulum hardness, tensile strength and glass transition temperature, it was even able to surpasses the properties of its fossil-based counterpart.

Degradable, anticorrosive, and fluorescent waterborne polyurethanes from vegetable oil internal emulsifiers for adhesives and strain sensor

In this work, three soybean oil internal emulsifiers with different −OH functionalities (203.03 ∼ 219.45 mg KOH·g−1) were prepared via the ring-opening reaction of epoxidized soybean oil (ESO) attacked by phosphoric acid. The soybean oil internal emulsifiers and castor oil (C.O) were employed to produce an array of DMPA- (dimethylol propanoic acid-) free anionic waterborne polyurethane dispersions (PUDs) with high bio-based content (69.2%) by utilizing the phosphoryl groups in ionic form. The curing films exhibited good mechanical properties, thermal stability, and multifunctionality (degradability, fluorescence, and anticorrosion). The films (WPU-P5, WPU-P10, and WPU-P15) can be completely degraded in 4.5 wt% NaOH solution for 10 h at room temperature. In addition, the films also displayed fluorescence under 365 nm UV irradiation, and the change of fluorescent intensity during material stretching and damage, which hence could be used to detect material tensile behavior and material damage. Due to the corrosion inhibition performance of the phosphoryl group and its excellent adhesion to the metal substrate, the WPU-P15 film had the best corrosion resistance. The adhesive capacity of the films as pressure sensitive adhesive was characterized by the shear strength test, hanging weight time and peeling test. The WPU-P10 film had a shear strength of 1.66 MPa, a hanging time of 1 kg weight up to 10 h, and a peel stress of 0.67 MPa. The WPU-P15 film was also applied in strain sensing to detect human activity. These studies are bound to further expand the application range of vegetable oil-based WPU materials.

Antibacterial waterborne polyurethane coatings impregnated with in-situ formed and capped silver nanoparticles via p-sulfonatocalix[4]arene

The development of antibacterial nanocomposite coatings has been well studied in response to antibiotic resistance concerns. In this regard, silver nanoparticles incorporated waterborne polyurethanes (WPUs) are among the most attractive area due to their unique properties such as biocompatibility, reduced use of volatile organic compounds (VOC), easy construction, low viscosity, high adhesion to various surfaces, and rapid film formation. In this project, silver nanoparticles (AgNPs) were in-situ formed and simultaneously stabilized in the presence of sodium p-sulfonatocalix [4]arene (p-SC4A) as both reducing and stabilizing agents. Subsequently, the p-SC4A-stabilized AgNPs (p-SC4A/Ag) were incorporated into waterborne polyurethane, which was synthesized by the prepolymer mixing method. Examination of the structure and morphology of p-SC4A/Ag nanostructures using FT-IR, XRD, UV, SEM, and TEM analyses confirmed the synthesis of p-SC4A/Ag NPs with a smaller size than 50 nm. In addition, the various properties of WPU films with and without SC4A/Ag were evaluated by ATR-FTIR, XRD, SEM, ICP, TGA, and contact angle tests. The results showed that using p-SC4A macrocycles not only solves the agglomeration problem of silver nanostructures in waterborne polyurethane dispersions but also significantly improves bacteria-killing efficiency against the gram-positive S. aureus and gram-negative E. coli bacteria relative to pure WPU. The biocompatibility of WPU films was also evaluated, and the results showed that samples containing SC4A/Ag NPs have good biocompatibility in contact with L929 fibroblast cells.

Preparation and optimization of WPU dispersion from polyether/polyester polyols for film and coating applications

BackgroundCastor oil and polytetramethylene ether glycol (PTMG) are used as polyester and polyether polyols. The waterborne polyurethane (WPU) resin is synthesized from polyether/polyester polyols following a ketone and catalyst-free pre-polymerization process. MethodsWPU resins are prepared from PTMG/castor oil with various hydroxyl molar ratios, such as 1/0, 3/1, 1/1, 1/3, and 0/1. Significant findingsThe results indicate that the WPU dispersions has a long shelf-life, high colloidal stability, and narrow distribution of molecular size. The addition of castor oil can increase the proportion of the cross-linking density, hard segments and hydrogen bonds of the WPU molecular chain. The addition of PTMG/castor oil increases from the molar ratio 1/0 to 1/1, the tensile strength of WPU film increases from 17.1 MPa to 25.6 MPa; the T5% increases from 250°C to 262°C; the water swelling ratio at 24 h decreases from 33.2 g/g to 19.4 g/g. The results indicate the using PTMG/castor oil can improve the mechanical strength, water resistance, and thermal stability of WPU film. The WPU could be applied to wood coatings with high properties. This study provides a cleaner process for optimizing the performance of WPU resin, which can replace conventional ketone- and organotin-based films and coatings.