Water-based Polyurethane Dispersions Research Articles

Water-Based Polyurethane Dispersions: A Detailed Analysis of the Particle Charge Using Soft and Hard Particle Model.

Water-based polyurethane dispersions (PUDs) show a characteristic dependency of the electrophoretic mobility on the electrolyte concentration, which can be investigated by hard and soft particle models. For this purpose, additional information can be obtained by determining particle charges and electrostatic potentials. PUDs with different contents of an intrinsic ionic stabilizer and various polyol components were synthesized according to the acetone process. The particle charge was characterized by potentiometric acid-base titration, and the data of the titration curve were fitted assuming multiple functional groups with adaptable acid strengths. To investigate the electrostatic potentials, electrophoretic mobilities were measured as a function of electrolyte concentration and analyzed by soft and hard particle theory. Acid-base titration experiments indicated that not all detected ionic groups are located on the surface but are partly arranged inside the polymer particle, as evidenced by a significant decrease of the corresponding effective dissociation constant. The evaluation of the titration data and the electrokinetic experiments showed that the soft particle model of Ohshima is not suitable to reflect the actual particle charge. In contrast, the hard particle model can describe the measured electrophoretic mobility of the dispersions very well if the relaxation effect is taken into account. The dependency of the corresponding zeta potentials on the electrolyte concentration can be excellently modeled assuming a constant surface potential ψ0 and distance of the shear plane xs. Reasonable results are obtained for both parameters with only minor differences between the PUD series. Nonetheless, the electrokinetic surface charge densities calculated with respect to the surface potential are lower than expected from the titration results. Although our results indicate a more complex charge distribution in a peripheral layer, the hard particle model currently shows the best description of the electrokinetic behavior of the PUDs.

Recyclable Thin-Film Soft Electronics for Smart Packaging and E-Skins.

Despite advances in soft, sticker-like electronics, few efforts have dealt with the challenge of electronic waste. Here, this is addressed by introducing an eco-friendly conductive ink for thin-film circuitry composed of silver flakes and a water-based polyurethane dispersion. This ink uniquely combines high electrical conductivity (1.6×105 S m-1 ), high resolution digital printability, robust adhesion for microchip integration, mechanical resilience, and recyclability. Recycling is achieved with an ecologically-friendly processing method to decompose the circuits into constituent elements and recover the conductive ink with a decrease of only 2.4% in conductivity. Moreover, adding liquid metal enables stretchability of up to 200% strain, although this introduces the need for more complex recycling steps. Finally, on-skin electrophysiological monitoring biostickers along with a recyclable smart package with integrated sensors for monitoring safe storage of perishable foods are demonstrated.

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.

Полиуретаны, наполненные модифицированным базальтовым волокном

The use of basalt fiber as a reinforcing filler is mainly used instead of glass fibers due to its unique properties. Basalt fiber in comparison with glass has a 10-22% greater modulus, higher absolute strength after exposure to 400 °C, superior to glass in alkali and especially acid resistance, approximately identical in water resistance, i.e. close in properties to high-modulus glass fibers. However, it is most often used as a filler for concrete and other building structures. There is much less information about its use as a polymer reinforcing filler. The polymer matrix for creating polymer composite materials is most often epoxy resins, less often polyester. At the same time, there is practically no data on polyurethanes that have a unique combination of high strength indicators with elasticity and hardness, resistance to solvents and aggressive media, abrasion resistance, etc. The use of basalt fiber as a filler that increases the strength characteristics of polyurethanes and gives them specific properties can significantly expand the scope of their application. In this regard, this study attempts to use crushed basalt fiber as a reinforcing filler for polyurethanes. In order to increase the adhesion of the polymer matrix – filler system, an adhesive based on water-based polyurethane dispersion is used. Samples were obtained based on a polyurethane binder filled with basalt fiber in amounts up to 10.0 % by weight, treated with water-polyurethane dispersion with a concentration of 10 to 20 % by weight. The best complex of strength properties is provided by polyurethanes filled with basalt fiber in the amount of 1.0% by weight, treated with 15 % by weight water-based polyurethane dispersion. At the same time, the tensile strength increased by 15% compared to the same filling without processing and by 50% compared to the unfilled analog and amounted to 33.7 MPa. These changes are explained by a more uniform distribution of crushed basalt fiber in the polymer matrix and an increase in the adhesion interaction of fiber-adhesive-polymer matrix due to the biphilicity of the adhesive, as well as the same (polyurethane) nature of the adhesive and the matrix. The developed polymer composite materials have high hydrolytic resistance, as well as resistance to acetone and hexane. At the same time, the greatest degree of swelling did not exceed 0.9 % of the mass.

Engineering foam skeletons with multilayered graphene oxide coatings for enhanced energy dissipation

This work shows how to improve the energy dissipation of open-cell polyurethane (PU) foams by creating multilayered graphene oxide (GO) nano-architectures onto the struts via a modified dip-coating process. Pristine PU foams are alternately dip-coated with GO coatings and water-based polyurethane dispersions (PUD) for a given number of times. The GO coating morphologies are carefully adjusted and the inner energy dissipation mechanisms reach the optimized interfacial frictions of GO-PU and GO-GO. Along with the synergistic effect of the multiple interpenetrating structure of GO/PU coating phases, these engineered composite foams with extremely low GO content (~0.12 wt%) afford a significant increase of quasi-static energy dissipation (52%) and dynamic damping (76%) when compared with counterpart foams coated with the same number of pure PUD layers. The specific Young’s modulus and strength of the designed foams also show remarkable enhancements of 310% and 490% respectively compared with those of pristine PU foams.

Synthesis and Characterisation of New Water-Based Polyurethane Dispersion via Solvent-Free Prepolymer Mixing Process

A new type of water-based polyurethane dispersion (NWPUD) was synthesised from isophorone diisocyanate, polyethylene glycol (Mw = 400 g/mol and 1000 g/mol), dimethylol propionic acid, and 1,4-butanediol using the prepolymer mixing process and without the incorporation of any volatile organic solvent. The hard-/soft-segment molar ratio of NWPUD formulations was varied with higher values (i.e. 5 to 11) allowing excess diisocyanate to reduce the prepolymer viscosity. The formulation using polyethylene glycol 400 g/mol with a hard-/soft-segment molar ratio of 5 failed by solidifying upon dispersion in water. Using polyethylene glycol 1000 g/mol and varying hard segment content, successful NWPUD formulations were obtained, all with pH between 6 and 7. FT-IR spectroscopy was used for the identification of chemical structures and functional groups. The colloidal properties of NWPUD formulations such as particle size, zeta potential, and dispersion stability were investigated to demonstrate feasibility for application in industrial coatings. The size distribution of NWPUD formulations varied from heterogeneous to homogeneous when the hard-/soft-segment molar ratio was increased. It was found that formulations with hard-/soft-segment molar ratio between 7 and 11 exhibited the most desirable dispersion stability within the zeta potential range of -50 to -55 mV.

Electromechanical properties of polyamide/lycra fabric treated with PEDOT:PSS

One of the challenges in smart textiles is to develop suitable multifunctional materials that can address simultaneously several characteristics such as durability, stretchability, lightweight, and conductivity. Conductive polymers which showed success in different technological fields like polymer solar cells and light emitting diodes are promising in many smart textile applications. In this work, we treated a common polyamide/lycra knitted fabric with PEDOT:PSS for stretchable e-textiles. PEDOT:PSS, with DMSO as a conductivity enhancer and different ratios of water-based polyurethane dispersions as a binder, was applied to the fabric with simple immersion and coating applications. The effect of different application methods and binder ratio on the surface resistance of the fabric was monitored with four point probe electrical surface resistance measurement systems. Samples prepared by immersion technique are more uniform and have higher conductivity than those prepared by a coating technique. SEM images showed that PEDOT:PSS is incorporated into the structure in the immersion method while in the coating it is majorly present on the surface of the fabric. The tensile measurement showed that the acidic PEDOT:PSS and polyurethane dispersion coating has no adverse effect on the tensile strength of the fabric. The coated samples can be stretched up to 700% while still reasonably conductive. The resistance increases only by a small amount when samples were stretched cyclically by stretching 100%. Generally, samples prepared by the immersion method maintained better conductivity while stretching than those by a coating method. The washing fastness of the samples was also assessed.

Anionic water-based polyurethane dispersions for antimicrobial coating application

A new halo-ester diol has been synthesized by esterification reaction of trichloroacetic acid and pentaerythritol by using p-Toluenesulfonic acid as a catalyst. The synthesized diol was reacted with isophorone diisocyanates, polyester polyol, di-methylol propionic acid to form polyurethane dispersion. The antimicrobial properties of polyurethane dispersions were evaluated against Gram-negative E. coli and Gram-positive bacteria L. plantarum by Kirby–Bauer test. The structure of the diol was examined using Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance and mass spectroscopy. The physical, chemical and thermal properties such as viscosity, particle size, chemical resistance and DSC, XRD, SEM and GPC of polyurethane dispersion were evaluated. The significant effect of diol and its chain length, particle size and zeta potential properties of resulting polyurethane dispersion were investigated.

環境調和型水性ポリウレタン樹脂

環境調和型水性ポリウレタン樹脂

Anionic waterborne polyurethane dispersions from maleated cotton seed oil polyol carrying ionisable groups

A novel class of bio-based, DMPA free, catalyst free, anionic waterborne polyurethane dispersions (PUD) have been successfully synthesized. Hydroxylated cottonseed oil has been maleated using maleic anhydride to introduce hydroxyl groups and ionisable carboxyl groups. This maleated polyol (MAHCSO) has been employed to develop water-based polyurethane dispersions through a prepolymer method and chain extension with dihydrazides at the dispersion stage. The –OH groups of the MAHCSO formed urethane bonds, and the carboxylate groups acted as an internal ionizer to stabilize the polymer dispersion in water. The significant effect of the ionic content in the polyol (MAHCSO) and chain length of dihydrazide on particle size, physico-chemical, thermal and mechanical properties of the resulting PUD films were investigated.

Air-drying bio-based polyurethane dispersion from cardanol: Synthesis and characterization of coatings

Abstract Exploring bio-renewable materials to replace petroleum-based building blocks for advanced coatings has been a major thrust area for researchers for the development of eco-friendly and sustainable products. For the last few decades, there has been significant interest among coating researchers around the world to design water-based polyurethane dispersions (PUDs) that can be cured at ambient conditions. In the present work we synthesized auto-oxidizable PUDs based on cardanol as sustainable material that also provides self-crosslinking attribute to the PUDs. Such types of PUDs are expected to be suitable for water-based industrial protective primers. The cardanol-based intermediates and final products are characterized by FTIR spectroscopy for conformation of synthesis reaction and their structures. The dried films of the coatings, formulated using a suitable drier catalyst, exhibited improvement in mechanical properties and solvent resistance. The oxidative curing has also been investigated by FTIR and differential scanning calorimetry (DSC). The corrosion resistance properties of the coatings on steel substrate, as studied by using electrochemical impedance spectroscopy (EIS) technique also showed better performance for cross-linked films.

The waterborne polyurethane dispersions based on polycarbonate diol: Effect of ionic content

Three water-based polyurethane dispersions (PUD) were synthesized by modified dispersing procedure using polycarbonate diol (PCD), isophorone diisocyanate (IPDI), dimethylolpropionic acid (DMPA), triethylamine (TEA) and ethylenediamine (EDA). The ionic group content in the polyurethane-ionomer structure was varied by changing the amount of the internal emulsifier, DMPA (4.5, 7.5 and 10 wt.% to the prepolymer weight). The expected structures of obtained materials were confirmed by FTIR spectroscopy. The effect of the DMPA content on the thermal properties of polyurethane films was measured by TGA, DTA, DSC and DMTA methods. Increased DMPA amounts result in the higher hard segment contents and in the increase of the weight loss corresponding to the degradation of the hard segments. The reduction of hard segment content led to the elevated temperature of decomposition and to the decrease of the glass transition temperature and thermoplasticity. The atomic force microscopy (AFM), results indicated that phase separation between hard and soft segment of PUD with higher DMPA content is more significant than of PUD with lower DMPA content. The physico-mechanical properties, such as hardness, adhesion test and gloss of the dried films were also determined considering the effect of DMPA content on coating properties.

Waterproof Breathable Polymeric Coatings Based on Polyurethanes

The performance of environmentally friendly water-based polyurethane dispersions (PUD) for waterproof breathable coating was studied. The effect of the nature of PUD, number of coatings, incorporation of additives, and processing conditions on the breathable properties of cotton fabric was evaluated. The relative proportions of hydrophilic and hydrophobic components had a direct influence on the breathable properties of the coated cotton samples. The increase in hydrophilic component resulted in an increased water vapor penetration and lower water resistance to water penetration in the coated samples. For all the compositions, the durability of the coatings was found to improve with the incorporation of polymeric binder in the coating formulation. The air permeability values of the coated samples were found to be orders of magnitude lower than the control (uncoated) fabric sample.

Treatment of thermoplastic rubberwith chlorine bleach as an alternative halogenation treatment in the footwear industry

Avoidance of solvents in bonding operations is a current demand in the footwear industry. Halogenation of rubber soles with solutions of trichloroisocyanuric acid (TCI) in different solvents has been successfully used to improve bonding to the leather uppers. In this study, the use of chlorine bleach as an alternative water surface treatment for a rubber has been tested. A thermoplastic block styrene thermoplastic (TR) was treated with bleach to improve its adhesion to a water-based polyurethane dispersion adhesive (PUD). T-peel testing, scanning electron microscopy (SEM), contact angle measurements (ethanediol, 25°C), and infrared spectroscopy (ATR-IR) were used to analyze the modifications produced on the rubber surface. Adhesion values were obtained from T-peel testing of joints produced with similarly treated TR rubber test pieces. Different experimental variables were considered in this study, namely the immersion time (0.5-2 min) in bleach, the active chlorine content (43.9- 55.6 g/l) in the bleach, the addition of a wetting agent (1-octyl-2-pyrrolidone) to the bleach, and the application of the surface treatment using an ultrasonic bath. The treatment with bleach produced the chlorination of the hydrocarbon chains on the TR rubber surface and slightly changed the surface roughness. Chlorination of the TR rubber with bleach (free active chlorine=55.6 g/l) was fast and needed only 30 sec immersion in the reagent mixture to produce high adhesion. Furthermore, the active chlorine content in the bleach was critical to assure an adequate T-peel strength value. The addition of 1-octyl-2-pyrrolidone to the bleach increased the wettability of the rubber surface, although it was necessary to carry out the surface treatment in the ultrasonic bath to obtain adequate adhesion to the PUD adhesive. Thermoplastic styrene-butadiene rubber Water-based polyurethane adhesive Bleach Halogenation Water-based surface treatment Contact angle ATR-IR spectroscopy SEM T-peel strength

A new water-based chemical treatment based on sodium dichloroisocyanurate (DCI) for rubber soles in the footwear industry

A new water-based chemical treatment based on sodium dichloroisocyanurate (DCI) solutions for rubber soles of different natures is reported in this study. Different concentrations (1-5 wt%) of DCI and two rubber formulations (vulcanized styrene-butadiene rubber, R2; thermoplastic rubber, TR) were considered. The effects produced by treatment of the rubber soles with DCI were compared with the standard halogenation method using trichloroisocyanuric acid (TCI) solutions in an organic solvent (ethyl acetate). The effects of chlorination on the rubber surfaces were studied using contact angle measurements, ATR-IR spectroscopy, and scanning electron microscopy. The adhesion strength was obtained from T-peel strength tests on canvas/PUD adhesive/treated rubber joints. The adhesive used throughout this study was a water-based polyurethane dispersion (PUD). The surface treatment with aqueous DCI solutions modified the surface chemistry of both the TR and R2 rubbers, creating C—Cl moieties on the surface and removing the zinc stearate from the R2 rubber surface. The use of a low DCI concentration in water was less effective in modifying the TR rubber, but was sufficient to obtain good T-peel strength values for the R2 rubber joints. On the other hand, heterogeneities and cracks were created on the rubber surface (mainly on the R2 rubber surface), which may contribute to an increase in the mechanical interlocking with the adhesive. A noticeable increase in the T-peel strength and a cohesive failure in the rubber for the joints produced with TR rubber were obtained when the rubber was treated with aqueous DCI solutions. For the canvas/PUD adhesive/chlorinated R2 rubber joint, the failure was located in a thin surface layer on the canvas. Finally, the surface treatment with TCI in ethyl acetate produced a more significant surface modification on both the TR and the R2 rubber, creating deeper roughness on the R2 rubber surface. Consequently, higher peel strength values were obtained using TCI solutions in ethyl acetate. Furthermore, the T-peel strength values were high in all joints produced with TR rubber treated with either TCI solution in ethyl acetate or aqueous DCI solution.

Effect of process variables on molecular weight and mechanical properties of water-based polyurethane dispersion

Water-based polyurethane dispersions (PUD) were prepared by polyaddition reaction using poly (hexamethylene adipate) glycol (polyol 66), isophorone diisocyanate (IPDI), dimethylol propionic acid (DMPA), and 1,6-hexane diamine (HDA) as chain extender. Various formulations were designed to investigate the effects of process variables such as molar ratio of NCO to OH (NCO/OH), DMPA content, and neutralization degree on molecular weight and mechanical properties. Universal testing machine (UTM) was used for the mechanical properties of emulsion cast film of the PUD. The molecular weights were measured by gel permeation chromatography (GPC). Evolution of the weight average molecular weight ( M ̄ w ) and mechanical properties were significantly affected by the neutralization degree during the chain extension. It was found that the M ̄ w increased when the NCO/OH molar ratio increased, subsequently mechanical properties such as tensile strength and 100% modulus improved dramatically. However, the elongation decreased as the NCO/OH increased.

Movement and regeneration of epicuticular waxes through plant cuticles.

Regeneration of plant epicuticular waxes was studied in 24 plant species by high-resolution scanning electron microscopy. According to their regeneration behaviour, four groups could be distinguished: (i) regeneration occurs at all stages of development; (ii) regeneration occurs only during leaf expansion; (iii) regeneration occurs only in fully developed leaves; (iv) plants were not able to regenerate wax. Wax was removed from the leaves with water-based glue and a liquid polymer, i.e. water-based polyurethane dispersion. In young leaves these coverings could not be removed without damaging the leaves. After a few days, waxes appeared on the surface of these polymer films, which still adhered to the leaves. It is concluded that waxes move through the cuticle in a process similar to steam distillation. This hypothesis could be further substantiated in refined in vitro experiments. Wax isolated from Eucalyptus globulus was applied to a filter paper, subsequently covered with a liquid polymer and fixed onto a diffusion chamber filled with water. The diffusion chamber was put into a desiccator. After 8-10 days at room temperature, crystals similar in dimensions and shape to in situ crystals appeared on the surface of the polyurethane film. This indicates that waxes in molecular dimensions move together with the water vapor that permeates through the polymer membrane. Based on these results, we propose a new and simple hypothesis for the mechanism of wax movement: the molecules that finally form the epicuticular wax crystals are moved in the cuticular water current.