Waterborne polyurethane/acrylate: Comparison of hybrid and blend systems

Polyurethane/acrylate hybrid composites in a broad range of composition (10, 30, 50, 70 and 90 wt.% of acrylic content), were obtained by emulsion polymerization of acrylic monomers (methyl methacrylate/n-butyl acrylate/acrylic acid mixture) in the presence of preformed polyurethane chains with polymerizable terminal vinyl groups. Blends with the same acrylic content were also prepared by mixing polyurethane and acrylic dispersions. Samples were characterized by SEC, DLS, FTIR, UV, TEM, AFM, SAXS/WAXS and gel fraction content. Mechanical properties, Buccholz and pencil hardness, surface roughness and water contact angle of films were also determined. The effect of the acrylic content on morphology and film properties was also evaluated. Hybrids are crosslinked systems showing changes in the particle and film morphologies with increasing acrylic content. The properties of hybrid films show a non-linear behavior with the increase of the acrylic component, while physical blends exhibit a gradual behavior from PU to AC. FTIR results indicate better acrylic-polyurethane compatibility in hybrid systems than in physical blends. Hybrid composites with up to 70 wt.% of acrylic component are homogeneous by SAXS. On the other hand, AFM results show that blends are phase segregated systems at all composition levels.     

Hyperbranched polyurethane (HBPU)-urea and HBPU-imide coatings: Effect of chain extender and NCO/OH ratio on their properties

Effect of chain extender and NCO/OH ratio on the properties of hyperbranched polyurethane (HBPU)-urea and HBPU-imide coatings were examined. The NCO terminated pre-polymers were prepared by reacting the first (G1) and the second (G2) generation hyperbranched polyester polyols (HBP-G1 and HBP-G2) with excess diisocyanate. The excess NCO content of the prepolymer was reacted with different chain extenders viz., 3-aminopropyl triethoxysilane (APTES), pyromellitic dianhydride (PMDA) and N-hydroxyphthalimide (NHTM) to obtain HBPU-urea or HBPU-imide coatings. The structure–property relationships of the different coatings were investigated by FTIR peak deconvolution, and these data suggests the highest extent of hydrogen bonding interaction for PMDA-based coatings, which increases with increasing NCO/OH ratio. Film properties were evaluated by TGA, DMTA, UTM and contact angle measurements; these results were supported by FTIR deconvolution results. As per contact angle measurements, hydrophobicity of coatings increased by increasing NCO/OH ratio. The adhesive strength, abrasion resistance, alkali resistance, and gel content of the coatings were also evaluated.     

FT-IR and XPS studies of polyurethane-urea-imide coatings

A series of polyurethane (PU)-urea-imide coatings were synthesized by a systematic three-step reaction process. Initially isocyanate terminated PU prepolymers were prepared by reacting soft segments such as polyester polyols (prepared from neopentyl glycol, adipic acid, isophathalic acid and trimethylol propane) or polyether polyols (polypropylene glycol-1000) with hard segments such as 2,4-toluene diisocyanate or isophorone diisocyanate with NCO/OH ratio of 2:1. Heterocyclic imide ring into the PU backbone was incorporated by co-polymerization with pyromellitic dianhydride (PMDA) from the excess NCO groups in the PU prepolymer with an NCO/anhydride ratio of 1:0.5 and the surplus NCO content after imidization was moisture cured. PU-urea-imide coatings were also obtained by partial chain extension of the excess NCO groups in the NCO terminated PU-imide copolymers, and the remaining excess NCO groups were completely reacted with atmospheric moisture. The obtained polymers were analyzed with Fourier transform-infrared (FT-IR) and angle resolved X-ray photoelectron spectroscopy (AR-XPS). The type and change in intermolecular H-bonding interaction in the PU-urea-imide films with structural variables was identified by deconvolution of the FT-IR spectra using Origin 6.0 software through Gaussian curve-fitting method. The FT-IR analyses of the PU-urea-imide coating films show dependence of phase separation on the nature of chain extender. Surface characterization data from AR-XPS suggests the dependence of phase segregation behaviour on the nature of the chain extender, which also supports the FT-IR observations.     

Synthesis and properties of aqueous polyurethane dispersions: Influence of molecular weight of polyethylene glycol

Aqueous polyurethane dispersions (PUDs) have recently emerged as important alternatives to their solvent-based counterparts for various applications due to increasing health and environmental awareness. A series of aqueous polyurethane dispersions containing carboxylate anion as hydrophilic pendant groups were synthesized through step growth polymerization reaction using hexamethylene diisocyanate (HDI), 1,4-butanediol (1,4-BDO), dimethylol propionic acid (DMPA) and polyethylene glycol (PEG) of different molecular weight. Effect of PEG molecular weight was investigated on molecular structure, contact angle measurement, and physical and adhesive properties of PU emulsions. Fourier transform infrared spectroscopy (FT-IR) was used to check the completion of polymerization reaction. Contact angle measurement indicated that the hydrophilicity of polymer increases by increasing molecular weight of PEG with a corresponding decrease in contact angle. Results of T-peel test showed a decrease in peel strength by increasing molecular weight of PEG. Moreover, solid contents%, drying time and storage stability suggested fast drying properties and greater stability of aqueous PU dispersions.     

Modification of aqueous polyurethane dispersions via tetraphenylethane iniferters

Aqueous polyurethane (PU) dispersions containing tetraphenylethane iniferter groups were prepared from 4,4′‐diphenylmethane diisocyanate, poly(propylene oxide)glycols, dimethylol propionic acid, and 1,1,2,2‐tetraphenylethane‐1,2‐diol. To improve the water resistance of the dispersions, methyl methacrylate monomers were added into these dispersions and block‐copolymerized onto the main PU chain. The viscosity and particle size of the dispersions were determined. Dispersion‐cast films were characterized in terms of the contact angle, the swell in water, and the mechanical properties. Contact‐angle and water‐swell measurements showed that the hydrophilicity of the films was decreased significantly when methyl methacrylate was polymerized in the presence of tetraphenylethane containing aqueous PU dispersions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2993–3000, 1999     

Synthesis and Properties of Aqueous Polyurethane/Polytert-butylacrylate Hybrid Dispersions

Aqueous polyurethane/polytert-butylacrylate (PU/Pt-BA) hybrid dispersions were prepared by polymerizing tert-butyl acrylate monomers that were emulsified by the waterborne polyurethane dispersions. The waterborne polyurethane dispersions, which contained no volatile solvent, were prepared by the prepolymer mixing process. The structure characteristics and properties of the hybrid dispersions were studied. A particle sizer and a viscometer were used to examine the physical characteristics of the dispersions. A Fourier transform infrared spectrophotometer and a gel permeation chromatograph were used to examine the structure of the hybrid composites. The thermal and mechanical properties were examined by a dynamic mechanical analyzer, a thermogravimetric analyzer, and an abrasion resistance tester. When the amount of ionic PU emulsifiers maintains constant, the average particle diameter and viscosity of the PU/Pt-BA hybrid dispersion become larger as more t-BA monomer was added and polymerized. As compared to the pure PU and Pt-BA polymers, the shifting of two T_gs in the composite toward each other may imply the improved compatibility between PU and Pt-BA through the hybridization process used in this study. The Pt-BA enhances the thermal and abrasion resistances of the PU/Pt-BA composites.     

聚氨酯-含氟丙烯酸酯复合乳液的制备及其表面性能

为了得到低表面自由能的聚氨酯-丙烯酸酯乳胶膜,以2,2,3,4,4,4-六氟丁醇甲基丙烯酸酯(FA)、苯乙烯(St)、丙烯酸丁酯(BA)为单体,在交联聚氨酯溶液(PU)中通过溶液聚合相转化法制得阳离子含氟聚氨酯-丙烯酸酯复合乳液(FPUA).通过FT-IR、TEM、粒径分析及接触角测试对聚合物结构、乳胶粒径及形态、乳胶膜表面性能进行了研究.研究表明,含氟丙烯酸酯的引入使聚氨酯-丙烯酸酯乳胶膜的表面自由能降低50%以上,常温固化的FPUA乳胶膜的表面自由能小于0.0172 J•m^-2;该复合乳液的粒子形态呈球形,粒径约为220 nm.     

Characterization of LLDPE/LLDPE-g-AA Blends by Contact Angle and FT-IR Methods

Abstract

Blends of linear low density polyethylene (LLDPE) and linear low density polyethylene-grafted-acrylic acid (LLDPE-g-AA) were prepared by melt mixing. The surface of films with different content LLDPE-g-AA were characterized through contact angle measurements and FT-IR spectroscopy. The contact angles of water and glycerol on films surfaces of LLDPE/LLDPE-g-AA blends decrease with increase of LLDPE-g-AA. From FT-IR spectra of the blends, the carbonyl peak strength on the films surface was calculated. It was found that larger the carbonyl peak strength, the lower the value contact angle for LLDPE/LLDPE-g-AA blends.     

Investigation of the effect of ZnO nanoparticles on the thermomechanical and microbial properties of hyperbranched polyurethane‐urea hybrid composites

Hybrid coatings of hyperbranched polyurethane‐urea (HBPUU) containing ZnO nanoparticles were prepared by mixing the hyperbranched polyurethane with the nanoparticles. The films were stored at room temperature and laboratory humidity conditions for one week to yield completely cured hybrid films. The ZnO nanoparticles were found to be well dispersed in the polymer up to 3 wt%. The structure–property relationship of various HBPUU–ZnO hybrid coatings was analysed using a Fourier transform infrared peak deconvolution technique with a Gaussian curve‐fitting procedure, while their viscoelastic, thermomechanical and surface morphology were studied using X‐ray diffraction, dynamic mechanical thermal analysis, thermogravimetric analysis, a universal testing machine, scanning electron microscopy, atomic force microscopy and contact angle instruments. The thermal stability and mechanical properties of the hybrid composite films improved with increasing ZnO content, which was believed to be due to thermal insulation in the presence of nanoparticles. Water contact angle data suggested that the hydrophobic character of the hybrid composites increased with increasing nanoparticle concentration. The antimicrobial property of the HBPUU–ZnO hybrid coatings was studied using the disc diffusion method. HBPUU–ZnO hybrid coatings showed good antimicrobial properties compared to HBPUU. Copyright © 2012 Society of Chemical Industry     

Waterborne polyurethane dispersions obtained by the acetone process: A study of colloidal features

Waterborne polyurethane (PU) dispersions were prepared from isophorone diisocyanate (IPDI), 2‐bis(hydroxymethyl) propionic acid (DMPA), 1,4‐butane diol (BD), poly(propylene glycol) (PPG), and triethylamine (TEA) by means of phase inversion through the acetone process. Changes in DMPA content, initial PU content in acetone, phase‐inversion temperature, evaporation conditions, and solvent nature were found to have a great impact on dispersion properties. Using a DMPA concentration of 0.30 mmol/g_pol, stable PU dispersions could only be obtained when the initial PU content in acetone was at least 60 wt %, and phase‐inversion temperature was lower than 30°C. However, when increasing the PU content to 75 wt %, stable dispersions were obtained using DMPA concentrations three times lower. Finally, viscosity curves during the water addition step as well as a phase diagram were determined to understand the particle formation mechanism. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and Properties of Waterborne Polyurethane Dispersions with Ions in the Soft Segments

A maleic anhydride modified castor oil (MCO) was used to prepare aqueous polyurethane dispersions (MCPUs) with ionic groups in the soft segments according to the prepolymer mixing process. The aliphatic polyether PU prepolymer was prepared with MCO and polyether glycol (Ng210) as polymeric glycol component. The prepolymer was dispersed under vigorous agitation by adding water and by chain extension with ethylene diamine. The effects of r _m (the mass ratio of MCO and Ng210) on the properties of the resultant waterborne polyurethanes (MCPUs) were studied. Structures and properties of the MCPU dispersions and their films were examined by FT-IR, particle size analyzer, DTG, DSC, WAXD, SEM and tensile tester. The MCPUs exhibit higher phase mixing with increasing of r _m.     

Synthesis, Characterization and Surface Properties of Cross-linked Polyurethane Dispersions Modified by Organosiloxane

A series of cross-linked polyether-polyester polyurethane dispersions modified with organosiloxane were prepared based on hydroxyl-terminated polydimethylsiloxane (HTPS) as hydrophobic component and 3-aminopropyl-triethoxysilane (APTS) as cross-linker as well as a bridge between polyurethane (PU) and polysiloxane (PSIL). It was discovered that polydimethylsiloxane segments were incorporated into PU chains chemically and organosiloxane was preferentially oriented toward the surface layer of the film by making a comparison of attenuated total reflection (ATR) spectra between the copolymer and the blend of PU and PSIL, which was further confirmed by investigation of electron spectroscopy for chemical analysis (ESCA). The relationships between surface properties of the film formed from polyurethane dispersion and organosiloxane content were also studied. The results showed that water contact angle of the film increased with the increase of organosiloxane content. Interestingly, it was also found that water contact angle of PUS film increased firstly and then decreased when film-forming temperature varied from 25℃ to 55℃.     

Convenient post-curing reactions for aqueous-based polyurethane anionomers

Anionic aqueous-based polyurethane (PU) dispersions were prepared by introducing carboxylic groups into a conventional PU backbone, followed by a water dispersion process. The resulting carboxylic groups containing aqueous-based PUs were amino-terminated anionomers. Two model reactions between an amino and a carboxylic group containing compounds with an epoxide and an aziridinyl compound, respectively were carried out at ambient temperature. Di-functional epoxide and aziridinyl compound were employed as the convenient single post-curing and dual-curing agents for these prepared PU dispersions. Di-aziridinyl compound was stable in aqueous PU dispersions as a latent curing agent when the pH value of the system was 8.0 or above. The curing behaviors of each PU curing system were monitored by measurements of the gel content, average particle size, zeta potential, and fluorescence spectra. The mechanical and thermal properties of these post-cured PUs were evaluated.     

Polyurethane/acrylate hybrids: Effects of the acrylic content and thermal treatment on the polymer properties

Polyurethane (PU)/acrylate hybrids with different acrylic contents (10, 30, 50, 70, and 90 wt %) were prepared by the polymerization of acrylic monomers in the presence of preformed PU chains with polymerizable terminal vinyl groups. Films obtained by the casting of polymer dispersions before and after thermal annealing were characterized by dynamic light scattering, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), TEM electron energy‐loss spectroscopy, differential scanning calorimetry, and gel fraction determination. Small‐angle X‐ray scattering (SAXS), wide‐angle X‐ray scattering, mechanical properties testing, atomic force microscopy, water contact angle testing, Buchholz hardness testing, and roughness testing of the films were also performed. The effects of the acrylic content and thermal treatment on the structure and properties were determined. TEM showed that a core–shell morphology was formed during polymerization. When the acrylic content increased, smaller particles without core–shell morphologies were observed. TEM energy‐loss spectroscopy studies confirmed this observation. Systems with up to 50 wt % acrylic component were homogeneous, as determined by SAXS, before and after thermal annealing. An attempt to incorporate a higher amount of acrylic component led to phase‐separated materials with a different morphology and, therefore, different properties. The relationship between the acrylic content and properties did not follow linear behavior. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Investigation of polyurethane (urea)/modified nano-calcium carbonate hybrid aqueous dispersions and their films

This investigation was focused on properties of polyurethane (urea) (PUU) by incorporating silica sol-modified nano-calcium carbonate (CaCO₃). The FT-IR spectroscopy and ζ potential measurement indicated the presence of a hybrid effect due to the hydrogen bonding between the nano particles and the polymer matrix. For these hybrid aqueous dispersions, the particle size decreased as the modified nano-CaCO₃ content increased, and the polydispersity index was very narrow (<1.20). Films prepared with the hybrid PUU aqueous dispersions exhibited excellent waterproof performance: the amount of water absorption was as low as 9.0 wt %, and the contact angle of water on the surface of this kind of film was as high as 93°C. TGA results indicated the high thermal stability of hybrid PUU polymers (223–255°C). The properties like tensile strength, hardness, and elongation at break were influenced by the modified nano-CaCO₃ content in the polymers. The hybrid PUU with 15 wt % modified nano-CaCO₃ content showed the optimum properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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.     

New high performance waterborne organic–inorganic hybrid materials from UV curing

The third generation glycerol based hyperbranched polyester (HBPE-3G) was synthesized by reacting glycerol and 2,2-bis(hydroxymethyl)propionic acid in a stoichiometric molar ratio. This polyester was used as preparation for waterborne hyperbranched UV cured polyurethane–silica hybrid coatings. The acrylic terminated waterborne coatings were prepared by modifying some of the hydroxyl groups HBPE-3G to acidic groups by reacting with maleic anhydride. The remaining hydroxyl groups were reacted with NCO terminated acrylate. Then the prepolymer was neutralized with triethyl amine and dispersed in water. The waterborne hybrid formulations were prepared by mixing 3, 5 and 10% of trimethoxysilylpropyl methacrylate (TMSPM) into the acrylic terminated waterborne coatings. The films were casted and cured under UV light. The various film properties were studied by XRD, AFM, TGA and DMTA instruments. TGA result suggests that the onset degradation temperature and final mass residue increase with increasing TMSPM concentration. DMTA results show that the storage modulus and glass transition temperature increase for the hybrid formulations with increasing TMSPM concentration. The structural characterization of the hybrid coatings was performed using FTIR spectroscopy. The tensile test demonstrated that the mechanical properties improve with the increasing TMSPM content. Surface morphology was studied by atomic force microscopy (AFM). AFM study revealed that TMSPM was crosslinked homogenously through the polymer matrix. The TGA and DMTA data suggest that higher thermal stability and glass transition temperature (T_g) for the TMSPM hybrid films compared to their pure counterparts were obtained with increasing the TMSPM content.     

Organically modified montmorillonite hyperbranched polyurethane–urea hybrid composites

The synthesis and characterization of hyperbranched polyurethane/clay (HBPu/o-clay) hybrid coatings prepared from HB aliphatic polyester polyols (HPs) and isophorone diisocyanate (IPDI) is reported. The HPs are prepared by reacting adipic acid (AA) separately with pentaerythritol (PE), trimethylol propane (TMP) and glycerol (Gly) in different mole ratios of 0.6:1.0, 0.8:1.0 and 1.0:1.0, respectively. K⁺-montmorillonite (K10) modified with cetyltrimethyl ammonium bromide (CTAB) is used to increase the compatibility between the clay and polymer matrix. The clay is well-dispersed into the polyester matrix by ultrasonication method. Later on, NCO capped HBPU prepolymer (NCO–HBPu) is synthesized from the clay-dispersed polyester by reacting with IPDI at NCO/OH ratio of 1.6:1.0. In the next step, excess NCO content in the binder is cured with moisture. The properties of different HBPu/o-clay hybrid coatings were studied by FTIR, TGA and DMTA instruments and a structure to property correlation is drawn. The deconvolution technique is used to identify the amount of hydrogen bonding present in the hybrid coatings. The TGA and DMTA result showed an enhancement of the thermal stability, room temperature modulus (E′) and glass transition value (T_g) for the clay modified hybrid coatings, and increases with increasing clay content. TGA results also suggest that the PE-based HBPu/o-clay hybrid coatings have higher thermal stability than TMP or Gly-based systems, which are in close agreement to the FTIR analysis.     

A study of the morphology of polyurethane–polystyrene interpenetrating polymer networks by means of small angle X‐ray scattering,modulated‐temperature differential scanning calorimetry,and dynamic mechanical thermal analysis techniques

The morphology of polyurethane–polystyrene (PU‐PS) (60 : 40 by weight) interpenetrating polymer networks (IPNs), in which internetwork grafting via 2‐hydroxyethyl methacrylate resides (HEMA) (1, 2.5, and 10 wt %, respectively) in the polystyrene networks has been studied by means of small angle X‐ray scattering (SAXS), modulated‐temperature scanning calorimetry (M‐TDSC), and dynamical mechanical thermal analysis (DMTA) techniques. With increasing internetwork grafting, the average size of domains became smaller (SAXS data) and the degree of component mixing increased (M‐TDSC and DMTA results). For the PU‐PS (60 : 40 by weight) IPN with 10% HEMA, the DMTA tan δ‐temperature plot showed a single peak. This DMTA result implied that the morphology of this PU‐PS IPN is homogeneous. However, the M‐TDSC data showed that three PU‐PS (60 : 40) IPNs samples (with 1, 2.5, and 10 wt % HEMA, respectively) were phase separated. For the three IPN samples, the correlation length of the segregated phases, obtained from SAXS data based on the Debye–Bueche method, did not show distinct differences. With increasing internetwork grafting, the scattered intensity decreased. This study concluded that for these IPNs, SAXS is sensitive to the size of domains and component mixing, but no quantitative analysis was given for the component mixing. M‐TDSC is suitable to be used to quantify the degree of component mixing or the weight fraction of interphases, and DMTA is sensitive to damping behavior and to phase continuity. However, DMTA cannot provide quantitative information about the degree of component mixing or the weight (or volume) fraction of the interphases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1958–1964, 2001     

Synthesis and characterization of hyperbranched polyester–urethane–urea/K10-clay hybrid coatings

A series of hyperbranched polyester–urethane–urea/K10-clay hybrid coatings (AHBPE-1 and AHBPE-2) have been prepared. Initially, the polyester polyols are synthesized separately in a step-wise manner using pentaerythritol (PE), phtallic anhydride (PTA) and trimethylol propane (TMP). The cetyltrimethylammonium bromide (CTAB) modified K10-clay is used as an organoclay for the hybrid composites preparation and dispersed into the polyester matrix by ultrasonication method. This clay-dispersed polyols are used for further synthesis. The degree of branching (DB), percentage of condensation reaction and quantity of dendritic (D), terminal (T) and linear (L) units present in the polyester are calculated, from the NMR peak integration value. The NMR result suggests that, there is formation of nearly 63% of condensation product in the polyester. A structure–property correlation is established, based on the hydrogen bonding effect with increasing clay content by using the FT-IR peak deconvulation technique. The dynamic mechanical and thermal analysis (DMTA) as well as thermo gravimetric analysis (TGA) results show, an increase in room temperature storage modulus (E′), glass transition temperature (T_g) and thermal stability of the hybrid coatings with increasing clay content and NCO/OH ratio. The contact angle measurement study suggests that, the hydrophilicity of the hybrid films increases with increasing clay content and decreases with increasing NCO/OH ratio.