Syntheses and self-assembly of novel polyurethane–itaconic acid copolymer hydrogels

Novel physically crosslinked polyurethane–itaconic acid (PU–I) copolymer hydrogels were synthesized by the macroiniferter-controlled radical polymerization method. The structures of the PU–I copolymer hydrogels were characterized by ¹H NMR, FTIR, GPC, and DSC. The water contact angles and self-assembly of the PU–I copolymer hydrogels have been investigated. The results revealed that PU–I copolymer hydrogels have good hydrophilicity, so the water contact angles of polyurethane could be easily adjusted by controlling the content of the hydrophilic vinyl monomers. The PU–I copolymer hydrogels were subjected to solvent-induced self-assembly in THF + water to construct a variety of morphologies. The morphology of the PU–I copolymer hydrogels’ self-assembly was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the mechanism of self-assembly was investigated.     

Mechanical performance of vinyl ester—polyurethane interpenetrating polymer network composites

In this study, a carbon fiber/vinyl ester-polyurethane interpenetrating polymer network (IPN) laminate composite was fabricated and characterized for the first time. The IPN matrix, consisting of a commercially available vinyl ester and polyurethane, was synthesized via a sequential method with vinyl ester as the rigid phase and polyurethane as the flexible phase. Good compatibility between the two phases in the matrix was achieved and confirmed via differential scanning calorimetry and dynamic mechanical analysis. The thermomechanical response of the IPN matrix was compared with that of an unmodified vinyl ester resin. The presence of the more ductile polyurethane in the IPN matrix depressed the glass transition temperature (from 94 to 84°C), but also served to improve damping response at all frequencies studied. Tensile and flexural tests were performed on the carbon fiber/IPN and carbon fiber/vinyl ester composites to determine their mechanical response. The IPN composite exhibited lower tensile properties than the vinyl ester composite. However, its flexural properties were on par with those of the vinyl ester composite.     

The effect of formulation variables on fouling-release performance of stratified siloxane–polyurethane coatings

The effects of formulation variables, such as type of polyol, solvent type and solvent content, and coating application method, on the surface properties of siloxane–polyurethane fouling-release coatings were explored. Fouling-release coatings allow the easy removal of marine organisms from a ship’s hull via the application of a shear force to the surface. Self-stratified siloxane–polyurethane coatings are a new approach to a tough fouling-release coating system. Combinatorial High Throughput Experimentation was employed to formulate and characterize 24 different siloxane–polyurethane coatings applied using drawdown and drop-casting methods. The resulting coatings were tested for surface energy using contact angle measurements. The fouling-release performance of the coatings was tested using a number of diverse marine organisms including bacteria (Halomonas pacifica and Cytophaga lytica), sporelings (young plants) of the green macroalga (Ulva linza), diatom ((microalga) Navicula incerta), and barnacle (Amphibalanus amphitrite). The performance of the majority of the coatings was found to be better than the silicone standards, Intersleek^® and Silastic^® T2. An increase in solvent content in the formulations increased the surface roughness of the coatings. Coatings made with polycaprolactone polyol appeared to be somewhat rougher compared to coatings made with the acrylic polyol. The adhesion strength of sporelings of Ulva increased with an increase in solvent content and increase in surface roughness. The adhesion strengths of Ulva sporelings, C. lytica, and N. incerta were independent of application method (cast or drawdown) in contrast to H. pacifica adhesion, which was dependent on the application method.     

Synthesis of waterborne polyurethane–silver nanoparticle antibacterial coating for synthetic leather

An antibacterial coating composed of silver nanoparticles and waterborne polyurethane was synthesized for use on synthetic leather. In this study, silver nanoparticles were prepared and used as nanofiller to impart antibacterial property. Silver nanoparticles were synthesized by using poly(vinyl pyrrolidone) as dispersant and sodium borohydride (NaBH₄) as reducing agent. Silver nanoparticles were characterized by transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analysis. The optimum dispersant was selected according to the zeta potential of dispersions. Waterborne polyurethane was synthesized by using isophorone diisocyanate, 2-bis(hydroxymethyl)propionic acid, triethylamine, and polytetramethylene ether glycol. Waterborne polyurethane–silver antibacterial coating was obtained by ultrasonic dispersion, and then cast on the surface of synthetic leather. The antibacterial property and coating adhesion were investigated. The results showed silver nanoparticles homogeneously dispersed in waterborne polyurethane and adhesion reaching grade 4. Antibacterial testing showed bacterial reduction of 99.99% for Escherichia coli and 87.5% for Staphylococcus aureus.     

Synthesis and fluorescence properties of a waterborne polyurethane–acrylic hybrid polymeric dye

A waterborne polyurethane–acrylic hybrid polymeric dye was prepared depending on soap-free emulsion polymerization method. The resulting polymeric dye composed of methyl methacrylate (MMA) monomer which was polymerized into polymethyl methacrylate (PMMA) as cores and waterborne polyurethane-based dye was synthesized by anchoring dye monomers (6-amino-2-cyclohexyl-benz[de]isoquinone-1,3-dione) to polyurethane chains as shells. The average particle sizes of the hybrid polymeric dye emulsions were found to be increased with the increase in MMA contents for MMA monomers. Compared with dye monomers, the absorption intensities and fluorescence intensities of the hybrid polymeric dye were enhanced with the increase of particle sizes. This study revealed that enhanced fluorescence intensity of the hybrid polymeric dye was mainly attributed to the hindered formation of exciplexes among dye monomers and an augmented light absorption area. It was found that the fluorescence intensity of the hybrid polymeric dye was increased with increasing temperature and the trend first increased and then decreased with increase in concentration. Furthermore, the fluorescence of the hybrid polymeric dye emulsions was found to be very stable and not sensitive to the fluorescence quencher.     

Influence of ingredients in water-based polyurethane–acrylic hybrid latexes on latex properties

Polyurethane–acrylic (PU–AC) hybrid latexes were prepared. Main monomers for PU preparation were isophorone diisocyanate, DMPA (dimethylol propanic acid) and polypropylene oxides (PPO) of different molecular weights. Acrylic monomers included butyl acrylate, methyl methacrylate and a crosslinker, trihydroxymethyl propane triacrylates (TMPTA). Several important ingredients in PU–AC latex preparation, such as surfactants, initiator, DMPA and PU/AC ratio, etc., were varied, and their effects on latex properties studied. Compared with surfactant free latexes, a sharp increase in particle size was observed in latexes done with 0.1% of surfactant regardless of the nature of the surfactants used (anionic, nonionic and anionic with long chain of amphiphilic alkylphenyl polyethoxylate). Further increase in surfactant content, however, led to latexes with smaller particle size and narrower particle size distribution when compared between latexes prepared using a same surfactant. When amount of the oil soluble initiator, azobisisobutyronitrile, was increased, AC monomers conversion was increased. It is interesting to observe that PPO with long propylene oxides brought about larger particle size combined with broader size distribution and less charge on particle surface; whereas lower DMPA levels led to latexes also of larger size combined with broader size distribution but more charges on particle surface. AC monomer crosslinker, TMPTA, contributed to reduce particle size, narrower size distribution and lower particle surface charges. By increasing AC amount in PU–AC latex, latex particle size significantly increased accompanied by a remarkable increase in particle surface charges. Mechanisms of particle formation and of DMPA stabilization were discussed in order to understand the experimental results.     

Development of moisture cure polyurethane–urea coatings using 1,2,3-triazole core hyperbranched polyesters

This article reports the development of moisture cure polyurethane–urea coatings. The coating has been developed using different generations of novel 1,2,3-triazole core containing hyperbranched polyester polyols (THBP). For the synthesis of THBP, the core molecule, tetra hydroxyl-terminated di-triazole (THTD), has been synthesized by click reaction involving ethylene diazide and 2-butyne-1,4-diol. The polycondensation reaction between the core THTD and 2,2-bis (hydroxymethyl) propionic acid (Bis-MPA) at different mole ratios has been used to get first (THBPG-1), second (THBPG-2), and third (THBPG-3) generations of triazole core hyperbranched polyesters. The structural investigations of these THBPs have been carried out by ¹H NMR, ¹³C NMR, and FTIR spectroscopy. The different generations of THBPs were further reacted with 1-isocyanato-4-[(4-isocyanatocyclohexyl) methyl] cyclohexane (H₁₂-MDI) at OH:NCO ratio of 1:1.2 to get –NCO terminated triazole core hyperbranched polyurethanes. They were cured under atmospheric moisture to get hyperbranched polyurethane–urea coatings and were named as THBPUG-1, THBPUG-2, and THBPUG-3. FTIR has been used to confirm the formation of polyurethane coatings. The TGA and DMTA have been used to determine the thermal stability and dynamic mechanical properties of the coatings, respectively. The corrosion resistance properties of the coatings have been studied by salt spray and electrochemical test. The coatings were also evaluated for microbial resistance. The results indicate that the thermal stability, glass transition temperature, and corrosion resistance properties increase with an increase in generation number of THBPs used for coating development. All three generations of coating films show excellent antimicrobial activity. Based on overall combined structure–property relationship study, these types of coatings will be useful as multifunctional applications in marine and moist environments.     

Structure–property correlation study of hyperbranched polyurethane–urea (HBPU) coatings

This paper deals with the structure–property relation of different HBPU coatings based on the variation of parameters like, NCO/OH ratio, generation number and type of diisocyanates used. For this, the NCO terminated HBPU prepolymers were synthesized first by reacting the different generation hyperbranched polyesters (HBPs) with excess diisocyanates. In the next step, these HBPU prepolymer coated films were completely moisture cured to get the desired HBPU coatings. The synthesized polymers were confirmed by ¹H, ¹³C NMR and FT-IR spectroscopy methods whereas structure–property relation was drawn from the FT-IR peak deconvolution technique. The degree of branching (DB) and percent composition of different structural units present in the HBPs were calculated from the ¹H and ¹³C NMR data by using Fretch equation. The melt viscosity study of different HBP samples suggests that most polyester sample showed Newtonian behavior. The coating film properties were studied by DMTA, TGA, UTM, and contact angle measurement instruments. DMTA and TGA data shows that the increase of NCO/OH ratio and generation number had a favorable impact on storage modulus (E′), glass transition temperature (T_g), onset degradation temperature (T_1ON) and char residue values of the coatings. The contact angle and UTM data suggest that the hydrophobicity and tensile strength increases but flexibility decreases with increasing the NCO/OH ratio.     

Molecular design and hygrothermal resistance of high-toughness polysiloxane–polyurethane block copolymer composite adhesives

With the development of new energy sources, the demand for aluminum composite films for power batteries is expanding; at the same time, higher requirements have been put forward for aluminum composite films and adhesives. Polyurethane, as the binder of aluminum composite films, strongly affects the performance of aluminum composite films when exposed to moisture and high temperature and can lead to delamination. This thesis prepares a polyurethane and silicone block copolymer composite adhesive by adjusting the ratio of hard and soft polyurethane segments to obtain polyurethane (PU) with excellent flexibility. On the basis of block copolymerization with bis-amino-terminated organosiloxane (ATPS), obtained excellent flexibility, high peel strength, moisture resistance, and heat resistance from a polysiloxane-based polyurethane composite adhesive (PUSR). The properties are also tested using tensile tests and peel strength tests. The test results show that by adjusting the ATPS content, the flexibility and hydrophobicity of the PUSR composite adhesive further improved, with a tensile strength of 36 MPa, an elongation at break of 757%, and bonding performance of 11 N/15 mm. Additionally, the damp heat resistance of 6 N/15 mm, exceeding the international standard of 3 N/15 mm, in the power battery soft package aluminum–plastic film has potential application prospects.     

The effect of the heat treatment of spruce wood on the curing of melamine–urea–formaldehyde and polyurethane adhesives

The effect of the heat treatment of spruce wood on the curing of melamine–urea–formaldehyde (MUF) and polyurethane (PUR) adhesives was monitored by measuring their rheological properties by means of a rheometer. Instead of the standard aluminium discs, wooden discs, made from heat-treated wood with different degrees of thermal modification and conditioned in different climates, were used. The wooden discs provided more realistic curing of the adhesives compared to the real-life bonding of wood, because of solvent absorption. The results of the rheological measurements suggested that the modified wood inhibited the curing of MUF and PUR adhesives. The curing of the MUF adhesive was slower because of the reduced absorption of water from the adhesive. The curing of the one-component PUR adhesive was affected by the lower moisture content (MC) of the modified wood.     

Facile fabrication of durable superhydrophobic fabrics by silicon polyurethane membrane for oil/water separation

Nowadays, oil contamination has become a major reason for water pollution, and presents a global environmental challenge. Although many efforts have been devoted to the fabrication of oil/water separation materials, their practical applications are still hindered by their weak durability, poor chemical tolerance,environmental resistance, and potential negative impact on health and the environment. To overcome these drawbacks, this work offers a facile method to fabricate the eco-friendly and dur...     

Effects of a silane coupling agent on the exfoliation of organoclay layers in polyurethane/organoclay nanocomposite foams?

An attempt was made to synthesize polyurethane (PU)/organoclay nanocomposite foams with high thermal insulation properties. The organoclay was modified by polymeric 4,4′‐diphenylmethane diisocyanate (PMDI) with a silane coupling agent. The structure of the organoclay‐modified PMDI with the silane coupling agent was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Transmission electron micrographs and wide‐angle X‐ray diffraction patterns showed that the interlayer distance increased for the PU/organoclay nanocomposites with the addition of the silane coupling agent. It was expected that the distance between the organoclay layers would increase and that the organoclay would be dispersed on a nanoscale in the PU matrix because of the organic/inorganic hybrid bond formation between the organoclay and silane coupling agent. Compressive and flexural strengths of the PU/silane coupling agent/organoclay nanocomposite foams were similar to those of the PU/organoclay nanocomposite foams. However, the thermal conductivity appreciably decreased from 0.0250 to 0.0230 W/m h °C in the PU/silane coupling agent/organoclay nanocomposite foams. Scanning electron micrographs showed that the cell size of the PU/silane coupling agent/clay nanocomposite foams also decreased. On the basis of these results, it is suggested that the smaller cell size and lower thermal conductivity of the PU/silane coupling agent/organoclay nanocomposite foams were mainly due to enhanced exfoliation of the organoclay layers by the silane coupling reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Properties and interfacial bonding of regenerated cellulose films coated with polyurethane–chitosan IPN coating

Water-resistant films were prepared by coating a castor oil-based polyurethane–chitosan (PU–CH), in which grafted interpenetrating polymer networks (IPNs) were produced, on a regenerated cellulose (RC) film. The tensile strengths of the coated films cured at 90°C for 5 min reached 853 kg cm⁻² (dry state) and 503 kg cm⁻² (wet state) and were obviously higher than those of the films of uncoated and coated with PU coating. Moreover, the coated films have excellent water resistivity, low vapor permeability, and good size stability, and their optical transmittance is even better than that of the RC film in the range of 400–800 nm. The interfacial structure of the coated films was investigated by using spectroscopy infrared, ultraviolet spectroscopy, transmission electron microscopy, and electron probe microanalysis. It was shown that the strong interfacial bonding with chemical and hydrogen bonds between the RC film and the coating exists. The PU prepolymer in the IPN coating penetrated through the interface into the RC film and partly crosslinked with the cellulose, forming a semi-IPNs. The chitosan in the PU–CH coating plays an important role not only in accelerating the cure of the coating but also in improving the mechanical properties and biodegradability of the coated film. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1313–1319, 1998     

Synthesis of Diels–Alder bond and hydrogen bond synergistic shape memory self-healing polyurethane elastomers

Self-healing materials exhibit the ability to repair damage and restore their function. Shape memory assisted self-healing (SMASH) materials are smart materials that automatically close localized microscopic cracks and repair these cracks by bonding damaged surfaces. A novel temperature-responsive SMASH polymer composite was established by introducing Diels–Alder bonds (D–A) in polyurethane. In this article, dynamic D–A produced by the polymerization of furfurylamine and 4,4’-bismaleimidodiphenylmethane was introduced into the molecular chain to enable the polyurethane elastomers containing D–A bonds to acquire self-repairing capability. The self-healing properties of the synthesized material were examined using polarized light microscopy, which revealed excellent fracture healing. The mechanical properties before and after healing were tested, in which the initial maximum tensile strength of the material could reach 7.9 MPa, and the maximum tensile strength after self-healing was 7.3 MPa, with a repair rate of 91.8%; the maximum elongation was 585.9%, and the maximum elongation after self-healing was 469.5%, with a repair rate of 80.1%. In addition, this material has excellent repair performance for microcracks of different scales, and the micromolten part of the surface after heating can fill the micrometer cracks, play the role of antiaging, and extend the service life of the material.     

Synthesis of α,ω-hydroxyalkyl telechelic polydimethylsiloxane soft segments and preparation of waterborne polyurethane–polydimethylsiloxane block copolymers

In this paper, by optimizing synthesis process of α,ω-hydroxyalkyl telechelic polydimethylsiloxane, α,ω-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)polydimethyl siloxane (PMTS), the yield of hydrosilylation product, 1,3-bis(glycidoxypropyl) tetramethyldisiloxane exceed 86.5%. By tracing the change of methanol (gravimetry) and measuring the change of molecular weights of polydimethylsiloxanes at different reaction time (titration), the optimum reaction time of methoxylation reaction and ring-opening polymerization was determined as 8 and 12 h. Using α,ω-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)polydimethyl siloxane with different molecular weights, waterborne polyurethane–polydimethylsiloxane block copolymer were prepared. The influences of molecular weights and content of α,ω-hydroxyalkyl telechelic polydimethylsiloxane on the waterborne polyurethane–polydimethylsiloxane block copolymers were investigated in detail. The addition of α,ω-hydroxyalkyl telechelic polydimethylsiloxane could improve the water-resistance property obviously and increase the elongation at break. However, the mechanical property was reduced with increase of content and molecular weight of α,ω-hydroxyalkyl telechelic polydimethylsiloxane.     

Polyoligomeric silsesquioxane (POSS)–hydrogenated polybutadiene polyurethane coatings for corrosion inhibition of AA2024

A series of coatings were developed that help prevent corrosion of aluminum alloy 2024 (AA2024). The coatings were based on an aliphatic polyurethane–polyoligomeric silsesquioxane (PU–POSS) resin. The materials were selected to exhibit a high level of hydrophobicity, which is expected to increase the moisture barrier properties, and thereby improve corrosion prevention. In addition, corrosion inhibitors (free molecules or encapsulated) were introduced into the coatings to improve corrosion resistance. The performance of the coatings was quantified using electrochemical impedance spectroscopy (EIS) and salt fog testing. Results from various formulations show that the hardness of the coating can be controlled by adjusting the ratio of POSS to hydrogenated hydroxyl terminated polybutadiene in the formulation. The coatings also had remarkable barrier properties, fast curing, and very high adhesion to the treated AA2024 substrate, all of which are expected to improve the anti-corrosion properties of the coatings. The best corrosion protection of AA2024 was observed in a transparent 10 μm thick PU–POSS bilayer coating that contained a mixture of sodium-2-mercaptobenzothiazole (i.e., NACAP) and benzotriazole-laden hydrotalcite. It was found that only certain corrosion inhibitors (free molecules or encapsulated) improve the anti-corrosion properties of the coating, whereas other corrosion inhibitors may actually degrade the coating performance.     

Effects of NCO:OH ratio on the mechanical properties and chemical structure of Kraft lignin–based polyurethane adhesive

ABSTRACT

This work aimed to evaluate the influence of the aliphatic and aromatic hydroxyl level on the polyurethane adhesive property and chemical structure. This adhesive was obtained through the reaction of technical Kraft lignin (TKL) as polyol with diphenylmethane diisocyanate (MDI). Thus, lignopolyurethane adhesives were obtained with NCO:OH ratios of 0.8:1.0, 0.9:1.0, 1.0:1.0, 1.1:1.0, and 1.2:1.0. Initially only the TKL aliphatic hydroxyl level was taken into consideration in the stoichiometry in order to define the mass ratio between MDI and polyol. Subsequently, lignopolyurethane adhesive was obtained using the same NCO:OH ratios considering TKL total hydroxyls’ level, and aromatic and aliphatic hydroxyls. The chemical structures of the synthesized adhesives were analyzed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (¹³C NMR). The mechanical property of the adhesively bonded joints, comprising wood substrates and synthesized adhesives, was measured using single lap shear tests. Results illustrated that by increasing the NCO:OH ratio, there is an increase in the free isocyanate content leading to higher shear strength values. Higher free isocyanate content leads to MDI dimer formation in the lignopolyurethane structure.     

Improved gas transport properties of polyurethane–urea membranes through incorporating a cadmium-based metal organic framework

The increasing need for more efficient separation processes has motivated the development of polymer membranes that can provide fast and selective transport. In this work, cadmium-based metal–organic framework (MOF) nanoparticles and a polyurethane–urea (PUU) elastomer were synthesized. New mixed-matrix membranes (MMMs) were then fabricated from the nanoparticles and the PUU. SEM images verified that embedding the nanoparticles changes the morphology of the PUU and the nanoparticles disperse well in the PUU due to satisfactory compatibility of the polymer and nanoparticles. Fourier transform infrared spectroscopy and X-ray diffraction analysis confirmed the dispersion of the nanoparticles in the soft segment of the PUU. With increased temperature, gas permeabilities of the MMMs improved but their sieving ability deteriorated. An MMM incorporating 2.5 wt % of the MOF showed a CO₂ permeability of ~140 barrer and a CO₂/N₂ selectivity of ~30, which are 89 and 38% higher than those of the pristine membrane. Gas permeation tests showed that the higher CO₂/N₂ selectivity of the MMMs was due to improved solubility selectivity and the higher CO₂ permeability was a result of improved CO₂ diffusivity and solubility coefficients. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48704.     

Self-assembly of silver–graphene hybrid on electrospun polyurethane nanofibers as flexible transparent conductive thin films

A method of integrating hybrid thin films of graphene nanosheets (GNSs) and silver nanoparticles (AgNps) by in situ chemical reduction to prepare transparent conductive films (TCFs) is studied. The surface functional groups of graphite oxide (GO) serve as nucleation sites of silver ions for adsorption of AgNps. To fabricate conductive films with high transmittance, polyurethane (PU) nanofibers are introduced to help construct two-dimensional conductive networks consisting of AgNps and GNSs (AgNps–GNSs). This method requires only a low percentage of conducting AgNps–GNSs covering the transparent substrate, thereby improving the transmittance. The flexible GNSs serve as nanoscale bridges between conductive AgNps and PU nanofibers, resulting in a highly flexible TCF. The optical transmittance can be further increased after melting the PU nanofibers at 100 °C. A fused film obtained after electrospinning (ES) a PU solution for 120 s and immersion in 0.05 wt.% AgNp–GNS (5:1) solution has a surface resistance of 150 Ω/sq and 85% light transmittance. Mechanical testing shows that AgNps–GNSs on flexible substrates yield excellent robustness. Thus, TCFs with a 3:1 ratio of AgNps:GNSs have high conductivity, good mechanical durability, and barely one order of magnitude increase of surface resistance when bent to an angle of 90°.     

Polymer/silica nanohybrids by means of tetraethoxysilane sol–gel condensation onto waterborne polyurethane particles

Stable waterborne polyurethane/silica hybrid dispersions were obtained by sol–gel reaction of tetraethoxysilane added to previously synthesized waterborne polyurethane nanodispersions. Two series of polyurethane/silica nanostructures with different silica contents were synthesized using pure polyurethane particles and polyurethane particles previously functionalized with (3-aminopropyl)triethoxysilane (APTES) as colloidal templates. The optimum experimental conditions for tetraethoxysilane sol–gel reaction (T = 75 °C and semi batch polymerization conditions) leading to the formation of silica/polyurethane aqueous nanodispersions were established. The presence of silica was confirmed using TGA, FTIR, ²⁹Si NMR and TEM. TEM images showed an excellent final dispersion of the silica nanoparticles in the polymer matrix when silane functionalized polyurethane nanoparticles were used.