Synthesis and characterization of hyperbranched polyesters and polyurethane coatings

Polyurethane (PU) coatings are widely used for variety of high‐performance applications in today's coating technology. The emerging hyperbranched polymers having three‐dimensional morphology have opened a new avenue to tailor the architecture of PU coatings. The methodology followed here is based on preparation of PU coatings from hyperbranched polyester. Initially, different hyperbranched polyester polyols (HPs) were synthesized by varying the hydroxyl‐terminated precursors that is, pentaerythritol, trimethylol propane or glycerol and keeping the diacid that is, adipic acid quantity constant at various mole ratios of 1:0.6, 1:0.8, 1:0.9, and 1:1, respectively. The obtained HPs were characterized by nuclear magnetic resonance (NMR) spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF)‐mass spectrometry, and Fourier transform‐infrared (FTIR) spectroscopy. The degree of branching and the quantity of different structural units present in the various HPs were calculated by integrating the quaternary carbon and carbonyl zone in ¹³C NMR spectroscopy. The extent of condensation in different HPs was also calculated from ¹H NMR spectra. Later on, NCO‐terminated PU prepolymers (NCO‐PU) were synthesized by reacting HPs with isophorone diisocyanate (IPDI) at NCO/OH ratio of 1.6:1. In the third step, the excess NCO content in the NCO‐capped PU prepolymers were reacted with atmospheric moisture and hyperbranched polyurethane (HPU) coatings were formed. The coating films were analyzed by FTIR and dynamic mechanical thermal analysis instruments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2673–2688, 2007     

Bio‐based hyperbranched polyurethane/clay nanocomposites: adhesive,mechanical, and thermal properties

The unison of vegetable oil‐based hyperbranched polymers with nanotechnology can unhook myriad of avant‐garde applications of such materials. Thus Mesua ferrea L. seed oil‐based hyperbranched polyurethane (HBPU)/clay nanocomposites and their performance, with special reference to adhesive strength, are reported for the first time. The nanocomposites of the hyperbranched polyurethane with organically modified nanoclay were obtained by ex situ solution technique and cured by bisphenol‐A‐based epoxy with poly(amido amine) hardener system. The partially exfoliated and well‐distributed structure of nanoclay was confirmed by XRD, SEM, and TEM studies. FTIR spectra indicate the presence of H‐bonding between nanoclay and the polymer matrix. Two times improvement in the adhesive strength and scratch hardness, 10 MPa increments in the tensile strength and 112°C more thermo‐stability have been observed without much affecting the impact resistance, bending, and elongation at break of the nanocomposites compared to the pristine epoxy modified HBPU system. Thus, the resulted nanocomposites are promising materials for different advanced applications including adhesive. Copyright © 2009 John Wiley & Sons, Ltd.     

Influence of number of functional groups of hyperbranched polyol on cure kinetics and physical properties of polyurethanes

Curing of polyurethane prepolymer with three hyperbranched polyol was studied using FTIR spectroscopy. The disappearance of the strong isocyanate absorption peak was followed with time and temperature to determine the reaction kinetics. It was shown that all the hyperbranched polyols followed the second order kinetic equation and the reaction rate enhanced with increase in the number of the functional groups of the hyperbranched polyol. Activation energy, activation enthalpy, and activation entropy were also measured. The swelling character of the polyurethanes was investigated with the help of gel fraction, degree of crosslinking, and average molecular weight between crosslinks. Atomic force microscopy indicated phase separated morphology of the cured polyurethanes. The thermal, mechanical, and thermomechanical properties were enhanced when the number of the functional groups in the hyperbranched polyols was increased. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 731–745, 2009     

Bio‐based hyperbranched polyurethane/Fe3O4 nanocomposites as shape memory materials

The bio‐based shape memory polymers have generated immense interest as advanced smart materials. Mesua ferrea L. seed oil‐based hyperbranched polyurethane (HBPU)/Fe₃O₄ nanocomposites were prepared by the in‐situ polymerization technique. The transmission electron microscopy confirmed the homogeneous distribution of the Fe₃O₄ nanoparticles in polymer matrix, whereas Fourier transform infrared spectroscopic study revealed the presence of strong interfacial interactions between them. The incorporation of Fe₃O₄ (0 to 10 wt%) into the HBPU resulted in an increase in tensile strength (5.5–15 MPa) and scratch resistance (3–6 kg). The thermo‐gravimetric analysis indicated the improvement of thermal stability (240–270°C) of the nanocomposites. The nanocomposites exhibited full shape fixity, as well as almost full shape recovery under the microwave stimulus. The shape recovery speed increased with the increase of Fe₃O₄ nanoparticles content in the nanocomposites. Thus, the studied nanocomposites might be used as advanced shape memory materials in different potential fields. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of organoclay on thermal and dynamic mechanical properties of novel thermoplastic polyurethane nanocomposites prepared by melt intercalation technique

Polymer nanocomposites based on thermoplastic polyurethane (TPU) containing organophilic montmorillonite (OMMT) were prepared by melt compounding method followed by compression molding. Different percentage of organically modified nanoclays (1, 3, 5, 7, and 9 wt%) was incorporated into the TPU matrix in order to examine the influence of the nanofillers on nanophase morphology and materials' properties. The microstructure morphology of the nanocomposites was examined by transmission electron microscopy (TEM), energy dispersion X‐ray analysis (EDX), wide angle X‐ray diffraction (WAXD), and atomic force microscope (AFM). The observation established that the organoclay is homogeneously dispersed and preferentially embedded in the TPU soft segment phase. Significant enhancement in the thermal stability of the nanocomposites was observed with the addition of the OMMT under thermogravimetric analysis (TGA). Dynamic mechanical properties of the TPU nanocomposites were analyzed using a dynamic mechanical thermal analyzer (DMTA), which confirms that the addition of OMMT has a strong influence on the storage and loss modulus of the TPU matrix. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and properties of hyperbranched polyurethanes,hyperbranched polyurethane copolymers with and without ether and ester groups using blocked isocyanate monomers

Starting from 3,5‐diamino benzoic acid, 2‐hydroxy propyl[3,5‐bis{(benzoxycarbonyl)imino}]benzyl ether, an AB₂‐type blocked isocyanate monomer with flexible ether group, and 2‐hydroxy propyl[3,5‐bis{(benzoxycarbonyl)imino}]benzoate, an AB₂‐type blocked isocyanate monomer with ester group, were synthesized for the first time. Using the same starting compound, 3,5‐bis{(benzoxycarbonyl)imino}benzylalcohol, an AB₂‐type blocked isocyanate monomer, was synthesized through a highly efficient short‐cut route. Step‐growth polymerization of these monomers at individually optimized experimental conditions results in the formation of hyperbranched polyurethanes with and without ether and ester groups. Copolymerizations of these monomers with functionally similar AB monomers were also carried out. The molecular weights of the polymers were determined using GPC and the values (M_w) were found to vary from 1.5 × 10⁴ to 1.2 × 10⁶. While hyperbranched polyurethanes having no ether or ester group were found to be thermally stable up to 217 °C, hyperbranched poly(ether–urethane)s and poly(ester–urethane)s were found to be thermally stable up to 245 and 300 °C, respectively. Glass transition temperature (T_g) of polyurethane was reduced significantly when introducing ether groups into the polymer chain, whereas T_g was not observed even up to 250 °C in the case of poly(ester–urethane). Hyperbranched polyurethanes derived from all the three different AB₂ monomers were soluble in highly polar solvents and the copolymers showed improved solubility. Polyethylene glycol monomethyl ether of molecular weight 550 and decanol were used as end‐capping groups, which were seen to affect the thermal, solution, and solubility properties of polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3877–3893, 2007     

Novel silver/polyurethane nanocomposite by in situ reduction: Effects of the silver nanoparticles on phase and viscoelastic behavior

A novel silver/poly(carbonate urethane) nanocomposite was prepared through in situ reduction of a silver salt (AgNO₃) added to a solution consisting of a commercial poly(carbonate urethane) dissolved in N,N‐dimethylformamide (DMF). In this system, the presence of the poly(carbonate urethane) was proved to protect the silver nanoparticles, whose formation was confirmed by means of UV–vis spectroscopy, from aggregation phenomena. The silver morphology developed in the solid state after DMF casting was imaged by FESEM. Homogeneous dispersion of silver nanoprisms in the poly(carbonate urethane) matrix was clearly observed. The effects of dispersion of silver nanoparticles within the poly(carbonate urethane) matrix were investigated by means of ATR‐FTIR and multifrequency dynamic mechanical thermal analyses. The obtained results revealed that the presence of silver nanoparticles modifies both the phase and the viscoelastic behaviors of poly(carbonate urethane). As a matter of fact, the hydrogen bond formation in the hard and soft segments was found to be hindered and the molecular motions of the soft segments were restricted, because a comparatively higher activation energy was required for the related α‐relaxation process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 344–350, 2008     

Properties and morphologies of UV‐cured epoxy acrylate blend films containing hyperbranched polyurethane acrylate/hyperbranched polyester

The properties and morphologies of UV‐cured epoxy acrylate (EB600) blend films containing hyperbranched polyurethane acrylate (HUA)/hyperbranched polyester (HPE) were investigated. A small amount of HUA added to EB600 improved both the tensile strength and elongation at break without damaging its storage modulus (E′). The highest tensile strength of 31.9 MPa and an elongation at break around two times that of cured pure EB600 were obtained for the EB600‐based film blended with 10% HUA. Its log E′ (MPa) value was measured to be 9.48, that is, about 98% of that of the cured EB600 film. The impact strength and critical stress intensity factor (K_1c) of the blends were investigated. A 10 wt % HUA content led to a K_1c value 1.75 times that of the neat EB600 resin, and the impact strength of the EB600/HPE blends increased from 0.84 to 0.95 kJ m^?1 with only 5 wt % HPE addition. The toughening effects of HUA and HPE on EB600 were demonstrated by scanning electron microscopy photographs of the fracture surfaces of films. Moreover, for the toughening mechanism of HPE to EB600, it was suggested that the HPE particles, as a second phase in the cured EB600 film, were deformed in a cold drawing, which was caused by the difference between the elastic moduli of HPE and EB600. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3159–3170, 2005     

Influence of varying hard segments on the properties of chemically crosslinked moisture‐cured polyurethane‐urea

Polyurethane prepolymers are widely used in the reactive hot melt adhesives and moisture‐cured coatings. The chemically crosslinked moisture‐cured formulation based on PEG‐1000 and isophorone diisocyanate was prepared with NCO/OH ratio of 1.6:1.0. Trimethylol propane was used as a crosslinking agent. The excess isocyanate of the prepolymer was chain extended in the ratio of 2:1 (NCO/OH) with different aliphatic diols, and 4:1 with different aromatic diamines. The polymer network maturation during moisture cure was followed by dynamic mechanical thermal analyzer (DMTA) instrument. The thermal and dynamic mechanical properties of the crosslinked polymers were evaluated using thermogravimetric analysis, differential scanning calorimetric analysis and DMTA. Surface properties were evaluated through angle‐resolved X‐ray photoelectron spectroscopy. The present article discusses the physical properties of moisture‐cured polyurethane‐urea (MCPU) containing chemical crosslinks in the hard segment. The complete moisture‐cured polymers showed amorous results toward room temperature modulus, tensile strength, hardness, thermal stability, and transparency. The surface properties showed the enrichment of soft segments. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 102–118, 2006     

Photopolymerization of waterborne polyurethane acrylate dispersions based on hyperbranched aliphatic polyester and properties of the cured films

A series of novel waterborne hyperbranched polyurethane acrylates for aqueous dispersions (WHPUD) based on hydroxy-functionalized hyperbranched aliphatic polyester Boltorn H20 were investigated and used as UV curable oligomers. The aqueous dispersions were electrostatically stabilized with carboxyl groups incorporated into their structures, which were neutralized by triethylamine. The photopolymerization kinetics of these WHPUDs was studied with respect to polymerization rates and unsaturation conversions in the presence of a photoinitiator using differential scanning calorimetry. The polymerization rates of the resins under UV irradiation and the gel contents in the cured films showed an increasing trend with higher concentration of acrylate functionality, which is in favor of the theory of radical chain polymerization. The mechanical and thermal behaviors of UV cured films of aqueous dispersions were evaluated by tensile testing and dynamic mechanical thermal analysis (DMTA). The results of DMTA investigations indicated that the glass transition temperature shifted to higher temperature as the content of the hard segment consisting of IPDI-HEA increased. Moreover, the storage modulus and pendulum hardness also increased with increasing the hard segment content. As the degree of neutralization increased, the T_g and tensile strength decreased, whereas, the elongation at break increased.     

Improved mechanical properties of epoxy‐based composites with hyperbranched polymer grafting glass‐fiber

A glass‐fiber, grafted by hyperbranched polymer with hydroxyl group (GF‐HBPH), reinforced epoxy‐based composite was evaluated for mechanical properties and compared with the neat epoxy and silanized glass‐fiber, GF‐APS. The epoxy/GF‐HBPH composites were studied by attenuated total internal reflectance infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, thermal gravimetric analysis, mechanical properties analysis, and field emission‐scanning electron microscopy. The results showed that the incorporation of GF‐HBPH could simultaneously enhance the mechanical properties of the epoxy composites. Field emission‐scanning electron microscopy images of the fracture surfaces of the test specimens were used to support the results and conclusions. Copyright © 2016 John Wiley & Sons, Ltd.     

Studies on the effect of the size of waterborne polyurethane nanoparticles on properties and performance of coatings

Present research work was performed utilizing prepolymer mixing process and varying NCO:OH mole ratios. Waterborne polyurethane dispersions (WBPUs) were prepared from phosphorous containing polyester polyol and isophorone diisocyanate. These prepolymers were neutralized by triethylamine followed by the addition of optimized quantity of water. Diethylenetriamine was used as a chain extender. These WBPUs were further coated on mild steel panels, glass panels, and wood. Chemical structure was confirmed using instrumental methods. Microtrac particle size analyzer was used to analyze the particle size. An impact of the size of nanoparticles on the performance of coatings was explained by different testing methods.     

Amphiphilic and hydrophobic surface patterns generated from hyperbranched fluoropolymer/linear polymer networks: Minimally adhesive coatings via the crosslinking of hyperbranched fluoropolymers

Hyperbranched fluoropolymers (HBFPs), based on benzyl ether linkages and having a large number of pentafluorophenyl chain ends, were crosslinked by a reaction with diamino-terminated poly(ethylene glycol) (PEG) or diamino-terminated poly(dimethyl siloxane) (PDMS) to form hyperbranched–linear copolymer networks of different compositions, structures, and properties. The crosslinking reactions involved the nucleophilic aromatic substitution of the pentafluorophenyl para-fluorines of HBFP by the amine functionalities of the respective telechelic linear segments. The contact angles, differential scanning calorimetry, thermogravimetric analysis, tensile measurements, and atomic force microscopy (AFM) were used to characterize the resulting network film samples. The surface wettability of the crosslinked materials was affected by the nature and amount of the linear polymer crosslinking agent employed. Amphiphilic polymer networks were formed by the incorporation of diamino-terminated PEG as a crosslinker, whereas diamino-terminated PDMS produced polymer networks of a hydrophobic character. The mechanical properties improved upon crosslinking, as measured by tensile testing. The mechanical integrity of the films was also found to improve upon crosslinking, as measured by AFM machining protocols. The AFM images revealed topographical morphologies that appeared to be the result of phase segregation of HBFP from PEG or PDMS; the dimensions of the phase-segregated domains were dependent on the stoichiometry of HBFP to the linear polymer and the thickness of the coating. As the content of PEG increased, fouling by human fibrinogen, used as a model protein, decreased. Further studies are in progress to determine the effects of the surface composition, morphology, and topography on the biofouling characteristics. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3531–3540, 2003     

UV curable waterborne polyurethane acrylate dispersions based on hyperbranched aliphatic polyester: effect of molecular structure on physical and thermal properties

A novel waterborne hyperbranched polyurethane acrylate for aqueous dispersions (WHPUDs) based on hydroxy‐functionalized hyperbranched aliphatic polyester Boltorn? H20 was investigated. The effects of structural composition and crosslinking density have been studied in terms of swellability by water, thermal degradation, viscosity changes as well as transmission electron microscopy (TEM) morphology. The swell ratio showed an increasing trend with the higher concentration of ionic group, which is due to the increased total surface area of particles. The results of thermogravimetric analysis (TGA) for cured WHPUD films indicated good thermal stability with no appreciable weight loss until 200°C. The activation energies were evaluated and were found in the range 154–186 kJ mol^?1. It was observed that an increase in hard segment content provoked the increases in thermal degradation temperature and activation energy of waterborne dispersions. The transmission electron photographs revealed that the average particle sizes of aqueous dispersions were in the range 30–125 nm. Owing to the enlargement of the stabilization site, the particle size decreased as the content of carboxyl group and degree of neutralization increased. The viscosity of WHPUDs increased rapidly with increasing the degree of neutralization. Moreover, water showed a favorable viscosity reduction effect. Copyright © 2004 John Wiley & Sons, Ltd.     

Syntheses and physical properties of two-component polyurethane flame-retardant coatings using chlorine-containing modified polyesters

Two-component polyurethane flame-retardant coatings were prepared by blending chlorine-containing modified polyesters (DCAOs) and polyisocyanate. DCAOs used were synthesized by polycondensation of dichloroacetic acid, a flame-retardant aliphatic carboxylic acid, with 1,4-butanediol, trimethylolpropane, and adipic acid. The content of dichloroacetic acid was varied in 10, 20, and 30 wt % for the polycondensation reaction. Various physical properties of these new flame-retardant coatings were comparable to nonflame-retardant coatings. They showed desirable properties for flame-retardant coatings such as rapid drying and 8–10 hours of pot-life. Coatings with 30 wt % dichloroacetic acid were not fired by the vertical burning test. © 1996 John Wiley & Sons, Inc.     

Chiral Azo polyurethane(urea): Preparation,optical properties and low power consumption polymeric thermo‐optic switch

Azo chromophore molecule (NPMBR) was synthesized by using 4‐nitroaniline, sodium nitrite and chiral reagent, R‐α‐methyl benzylamine. Then, NPMBR was polymerized with isophorone diisocyanate and polyether polyol to obtain novel chiral azo polyurethane(urea) (PUUR). The chemical structures of NPMBR and PUUR were characterized by FTIR and UV‐Vis spectroscopy. The UV‐induced trans/cis photoisomerization and reflex‐isomerization behaviors were investigated and the results indicated that the PUUR solution could undergo photochromism after irradiated by UV light. The measurements of refractive index and thermo‐optic coefficient (dn/dT) of PUUR were demonstrated at different wavelengths and different temperatures by ATR technique. By using CCD digital imaging devices, transmission loss of the internal waveguide was measured. The refractive index dispersions and Sellmeyer coefficients of PUUR were obtained by Sellmeyer equation. A Y‐branched switch based on thermo‐optic effect was proposed and the performance of switch was simulated. With branching angle of 0.143° and FD‐BPM method, the result showed that the power consumption of the thermo‐optic switch could be only 0.4 mW, and the response time of the switch could reach about 3 ms. It has a significant improvement in reducing the power consumption and response time compared with those of the normal Y‐branched polymer thermo‐optic switch. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Effect of process variables on mechanical properties of polyurethane/clay nanocomposites

This paper addresses the effects of operating variables on mechanical properties of polyurethane/clay nanocomposites including tensile strength, abrasion resistance, and hardness. The variables were prepolymer type, clay cation, clay content, and prepolymer–clay mixing time. The experiments were carried out based on the design of experiments using Taguchi methods. The nanocomposites were synthesized via in situ polymerization starting from two different types of prepolymers (polyether‐ and polyester‐types of polyol reacted with toluene diisocyanate), and methylene‐bis‐ortho‐chloroanilline (MOCA) as a chain extender/hardener. Montmorillonite with three types of cation (Na⁺, alkyl ammonium ion, and MOCA) were examined. Among the parameters studied, prepolymer type and clay cation have the most significant effects on mechanical properties. Polyester nanocomposites showed larger improvements in mechanical properties compared to polyether materials due to higher shear forces exerted by polymer matrix on clay aggregates during polymer–clay mixing. The original MMT with Na⁺ cation results in weak improvements in mechanical properties compared to organoclays. It is observed that the stress and elongation at break, and abrasion resistance of the nanocomposite samples can be optimized with 1.5% of clay loading. The morphology and chemical structure of the optimum sample were examined by X‐ray diffraction and FT‐IR spectroscopy, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and property study of UV-curable hyperbranched polyurethane acrylate/ZnO hybrid coatings

In the present work, the third generation hyperbranched polyester (HBPE-3G) based polyurethane acrylate (HBPUA-32)/ZnO hybrid coatings are prepared, by modifying 16 hydroxyl groups of HBPE-3G with an acrylic adduct. The HBPE-32 is prepared from the di-trimethylol propane and 2,2-bis(hydroxymethyl) propionic acid, converted into hybrid coatings by incorporating 1%, 3% and 5% nano ZnO powder into the polymer matrix. The ¹H, ¹³C NMR and FT-IR spectroscopy methods are used for structural characterization, degree of branching calculation and structure to property correlation study and various hybrid film properties are analyzed by TGA, DMTA, XRD and SEM instruments.     

Synthesis of a new hyperbranched‐linear‐hyperbranched triblock copolymer and its use as a chemical modifier for the cationic photo and thermal curing of epoxy resins

A new hyperbranched‐linear‐hyperbranched polymer was prepared in a one pot process by reaction of 4,4‐bis(4‐hydroxyphenyl)valeric acid and poly(ethylene glycol) (HPH). After characterization by ¹H and ¹³C NMR, SEC, DSC, and TGA, this polymer was used, in proportions of 5, 10, and 15 phr, as a chemical modifier in the UV and thermal cationic curing of 3,4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexyl carboxylate epoxy resin. The curing process was studied by calorimetry, demonstrating the accelerating effect of the hydroxyl groups present in HPH's structure. The morphology of the resulting thermosets depended on the curing system used, as demonstrated by FE‐SEM microscopy, but in both cases phase separation occurred. Thermosets obtained by thermal curing presented lower thermal stability than UV‐cured materials. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Structural and end‐group effects on bulk and surface properties of hyperbranched poly(urea urethane)s

The hydroxy end groups of aromatic and aliphatic hyperbranched poly‐(urea urethane)s prepared with an AA* + B*B₂ one‐pot method were modified with phenylisocyanate, butylisocyanate, and stearylisocyanate. The success of the modification reaction was verified with ¹H NMR and IR spectroscopy. Linear model poly‐(urea urethane)s were prepared, too, for comparison. The bulk properties of OH functionalized hyperbranched poly(urea urethane)s, compared with those of linear analogues and modified hyperbranched poly(urea urethane)s, were studied with differential scanning calorimetry, thermogravimetric analysis, and temperature‐dependent Fourier transform infrared measurements. Transparent and smooth thin films could be prepared from all polymer samples and were examined with a light microscope, a microglider, and an atomic force microscope. The properties of the polymer surface were examined by measurements of the contact angle and zeta potential. For all samples, the properties were mainly governed by the strong interactions of the urea and urethane units within the backbone, whereas the influence of the nature of the end groups and of the branched structure was reduced in comparison with other hyperbranched polymer systems. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3376–3393, 2005