Hybrid Emulsion Research Articles

RETRACTED: Synthesis of a silicone containing allylic monomer and its uses in the waterborne polyurethane/vinyl acetate–acrylic hybrid emulsion copolymers

A new silicone containing allylic monomer, allyl 3-(triethoxysilyl) propyl carbamate (ATESPC), based on (3-isocyanatopropyl) triethoxysilane (ICPTES) and allyl alcohol (AAL) has been synthesized for formulation of waterborne polyurethane (WPU). Then a series of new siliconized WPU, vinyl acetate (VAc)/2-ethylhexylacrylate (2-EHA) and ATESPC hybrid latexes P(VAc-2-EHA)/PU/Si have been successfully synthesized by the emulsion copolymerization in the presence of a WPU dispersion by using potassium persulfate (KPS) as an initiator. The WPU dispersion has been synthesized by a polyaddition reaction of hexamethylene diisocyanate (HMDI), on polypropylene glycol (PPG-1000) and dimethylol propionic acid (DMPA) as chain extender. The NCO chain ends being reacted with water (which act as a further chain extender producing some urea bonds). Films were obtained for different hybrid latexes of various compositions. The resulted monomer characterized by Fourier transformer infrared spectroscopy (FTIR), proton ( 1 H NMR), and carbon ( 13 C NMR) nuclear magnetic resonance spectroscopes, respectively. The copolymers also were characterized by using Fourier transform infrared spectroscopy (FT-IR). Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The morphology of copolymers was investigated by scanning electron microscopy (SEM) and then the effects of silicone concentrations on the water absorption ratio, was examined.

Effect of nanosilica content on properties of polyurethane/silica hybrid emulsion and its films

AbstractPolyurethane/silica hybrid emulsion (PUSi) was synthesized by the reaction of isophorone isocyanate, polyether polyol, hydrophilic nanosilica (A200), dimethylol propionic acid, trimethylol propane, and 3‐aminopropyltriethoxysilane (KH550). The films of the waterborne polyurethane (WPU) were prepared. The structure of the polyurethane was characterized by Fourier transform infrared spectrometer (FTIR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The particle size distribution and morphology of emulsion were examined. Influence of nanosilica content on the mechanical properties and solvent absorption of the cast films were also measured quantificationally. FTIR indicates that NH2 of KH550 reacted with NCO of polyurethane. TG analysis indicates that nanosilica can improve thermal stability of polyurethane. There is no clear effect of nanosilica on the glass transition of soft segments. It was found that greater mechanical properties of WPU were obtained when chemical networks were formed by sol‐gel process. As the nanosilica content increases, water absorption and ethanol absorption decreased. The particle size increases with increase of A200 content. PUSi hybrid emulsions are endowed with pseudoplasticity. The apparent viscosity of emulsions increased and then decreased with addition of A200. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis of Fluorinated Polyurethane/Polyacrylate Hybrid Emulsion Initiated by 60Co γ-Ray and Properties of the Latex Film

Based on the solvent-free method, novel fluorinated polyurethane/polyacrylate hybrid emulsions, dodecafluoroheptyl methacrylate (DFMA) as fluorinated monomer, were successfully prepared via emulsion polymerization without traditional emulsifier. For the purpose of increasing the grafting ratio of polyurethane and polyacrylate, 60Co γ-ray radiation polymerization had been adopted to enhance the hardness of latex film. The chain structure and polymerization progress were confirmed by the analysis of Fourier transform infrared spectroscopy. The grafting ratio of polymethyl methacrylate and polyurethane was obtained by calculating the ratio of N–H peak integral area and Ph(C=C) peak integral area. The effect of DFMA content on thermal stability, mechanical property and water resistance were investigated systematically by thermal weight loss analysis, tensile strength test, absorbed water ratio and water contact angle.

Waterborne Polyurethane Modified by Hydroxyl-Terminated Polyacrylate

In the presence of mercaptoethanol as chain-transfer agent,hydroxyl-terminated polyacrylate(PA) with a certain molecular mass was synthesized by solution free-radical polymerization of butyl acrylate( BA) and methyl methacrylate ( MMA ). The PA-PU-PA hybrid emulsion was obtained by reacting PA with polyurethane(PU) prepolymer in water. FTIR and 1H NMR results of the copolymer chain structure show that when PU /PA mass ratio declined,the acrylic content in the copolymer increased and the role of hydrogen bonds between PU soft and hard segment weakened. The composite particles had homogeneous core-shell structure in TEM photograph. Waterproof and heat resistant performance of the modified latex film were improved with the decrease of PU /PA mass ratio. Water absorption of the modified film dropped from 25% to 5% and the maximum mass loss temperature was increased from 369 ℃ to 432 ℃ .

Preparation of Organic/Inorganic Hybrid Polymer Emulsions with High Silicon Content and Sol-gel-derived Thin Films

A novel polymer/SiO 2 hybrid emulsion (PAES) was prepared by directly mixing colloidal silica with polyacrylate emulsion (PAE) modified by a saline coupling agent. The sol-gel-derived thin films were obtained by addition of co-solvents into the PAES. The effects of γ-methacryloxypropyltrimethoxysilane (KH-570) content and co-solvent on the properties of PAES films were investigated. Dynamic laser scattering (DLS) data indicate that the average diameter of PAES (96 nm) is slightly larger than that of PAE (89 nm). Transmission electron microscopy (TEM) photo discloses that colloidal silica particles are dispersed uniformly around polyacrylate particles and some of the colloidal silica particles are adsorbed on the surface of PAE particles. The crosslinking degree data and Fourier transform infrared (FT-IR) spectra confirm that the chemical structure of the PAES is changed to form Si-O-Si-polymer crosslinking networks during the film formation. Atomic force microscope (AFM) photos show the solvent induced sol-gel process of colloidal silica and the Si-based polymer distribution on the film surface of the dried PAES. Thermogravimetric analysis (TGA) curves demonstrate that the PAES films display much better thermal stability than PAE.

Strangeness at J-PARC

Strangeness nuclear physics is one of the main fields to be explored at the J-PARC Hadron Hall. The K − and π± beams at the K1.8 beam line will be used mostly for hypernuclear experiments. The γ-spectroscopy of Λ hypernuclei using the K −,π − reaction and the spectroscopy of neutron-rich hypernuclei via the π −,K + reaction are planned to be studied. As for Strangeness = − 2 systems, experiments for Ξ hypernuclear spectroscopy via the K −,K + reaction, double Λ hypernuclei by the hybrid emulsion method, and Ξ−-atomic X rays will be carried out.

Crosslinked polyurethane–epoxy hybrid emulsion with core–shell structure

An epoxy resin was used to prepare crosslinked polyurethane hybrid emulsion through the blocked NCO prepolymer mixing process. Due to their hydrophobicity, the amine chain extender, blocked –NCO, and epoxy are located inside the emulsion particles. Thus, the crosslinking reaction occurs mostly in the interior of the particles. In this way, the crosslinking density of the resin is increased without the use of solidifying agents or heating during film formation, and the stability of the emulsions remains uninfluenced. The effects of the type of amine chain extender and the type, dosage, and addition mode of the epoxy resin were studied in terms of mechanical properties and swelling properties in water and toluene of the cast films. Additionally, the stability of the single-pack hybrid emulsion was studied. The results showed that the sample prepared with diethylene triamine had good stability, chemical resistance, and high mechanical strength. The modulus and water resistance of the films increased with the epoxy resin content, which could reach 20 wt%. The type of amine chain extender affected the stability of the emulsions significantly. The molar ratio of NH/NCO at 1:1 led to the best film performance. The optimal temperature of the chain-extension reaction was approximately 80°C. The hybrid emulsions could be stored for at least 6 months without apparent performance changes.

Preparation and properties of urethane/acrylate composite by emulsion polymerization technique

Aqueous polyurethane–acrylic hybrid emulsions were prepared by semibatch emulsion polymerization of a mixture of acrylic monomers (styrene, butyl acrylate and acrylic acid) in the presence of polyurethane dispersion. Equivalent physical blends were prepared by mixing acrylic emulsion and polyurethane dispersion. The weight ratio between acrylic and polyurethane components was varied to obtain enhanced performance properties and microphase structure of hybrid latexes. The synthesized emulsion hybrids and physical blends were characterized by fourier transform infrared spectroscopy, thermogravimetric analysis. The experimental results indicate better acrylic–polyurethane compatibility in hybrid emulsions than in physical blends, resulting in improved chemical and mechanical properties. The blend ratio 50:50% (w/w) exhibited synergistic effects between the two polymers and revealed remarkable improvement in various coating properties over other blend ratios and the individual resin components.

STUDY OF NANO-SILICA/FLUORINATED ACRYLATE COPOLYMER HYBRID EMULSION AND THE POLYMERIZATION KINETICS

Perfluorinated polymers are of high scientific and technological interest owing to their unique characteristics.However,their utilization is limited due to their poor cohesiveness,film-forming properties and high cost.When perfluorinated polymers are incorporated with polyacrylate,remarkable properties are exhibited with higher performance price ratio;that is,oil and water repellency of the former is unmitigated while the mechanical strength and cohesiveness of the latter are retained.As an inexpensive functional component,incorporated silica can shield polymeric matrix from the UV,while reinforcement and improved thermal stability are achieved,as well as better rinse-resistance,perdurability and self-cleanness effects. In this paper,nano-silica and poly(MMA-co-nBAco-FA) were combined with covalent bonds.Not only extraordinary properties derived from each individual component were retained,but also a more intimate cooperation was provided between the twos,through an environment-friendly method. At first,the monodisperse silica was prepared in ethanol according to the well-known Stber procedure,followed by modification via addition of γ-methacryloxy propyltrimethoxysilane(MPS).Then,the nano-silica/poly(MMA-co-nBA-co-FA) hybrid emulsion was prepared via in-situ emulsion polymerization in the presence of MPS-grafted silica. The chemical compositions and morphologies of both nano-silica and silica/poly(MMA-co-nBA-co-FA) nanocomposites(NPs) were characterized by Fourier-transform infrared(FT-IR) spectrometry and transmission electron microscopy(TEM),respectively.From TEM images,it was obvious that uniform spherical nano-silica was obtained,with average diameter of 20 nm.FT-IR effectively proved the occurrence of MPS-grafting reaction.According to the amount of MPS added,the MPS-grafted density of nano-silica was determinated as 0.1716 μmol/m~2. Off-centre core-shell structures of silica/poly(MMA-co-nBA-co-FA) NPs were confirmed by TEM images.Approximately 50% of NPs had more than one single core due to the congregating of smaller particles when the diameters of the core were not larger than 100 nm.Under a low MPS-grafted density,not all of monomers were polymerized and connected with MPS on the grafted silica,and most of the polymer chains were twisted and absorbed around the core particles,followed by copolymerization with polymer layer copolymerized with MPS,resulted in an off-centre core-shell structure ultimately. Thermal stability of silica/poly(MMA-co-nBAco-FA) NPs was studied via thermal gravimetric analysis(TGA).The results showed that higher initiative decompose temperature was achieved with more nano-silica incorporated,which implicated the successful encapsulation of silica into NPs,as well as enhanced thermal stability. The surface properties of the latex films produced from silica/poly(MMAco-nBA-co-FA) NPs were also investigated by contact angle method and water absorption measurements.Obviously,the incorporation of silica and FA contributed to degressive surface-free energy,with a minimum value of 9.8 mN/m.Similarly,water absorption ratio decreased with increasing contents of nano-silica and FA.What worth noting was the abnormal polar and disperse component of surface-free energy,which might be attributed to nano-silica's incorporation and distribution while film-forming.Besides these,the kinetics of in situ emulsion polymerization,in which MPSgrafted silica with a low grafted density was introduced,had been investigated in details.The results can be summarized as follows: R_p∝~(0.25)[SiO_2]~(0.31)[I]~(0.66)~(0.757) while [SiO_2]8.9×10~-2 mol·L~-1,and R_p∝~(0.25)[SiO_2]~(-1.33)[I]~(0.66)[E]~(0.757) while [SiO_2]8.9×10~-2 mol·L~-1.The overall activation energy of the polymerization was calculated to be 83.15 kJ/mol.

Synthesis and properties of PDMS modified waterborne polyurethane–acrylic hybrid emulsion by solvent-free method

A new type of polysiloxane modified polyurethane–acrylic hybrid emulsion was synthesized by solvent-free method and the polysiloxane was introduced into the soft segment of polyurethane chains using dihydroxybutyl-terminated polydimethylsiloxane (PDMS). The formed film from the hybrid emulsion could provide obviously higher water-resistance property. The preparation technologies such as the content of carboxy group and acrylic monomer, the rate and the time of emulsification were discussed systematically. The chain structure and the particle size were confirmed by the analysis of Fourier transform infrared spectroscopy and transmission electron microscopy, respectively. The effect of PDMS content on the water resistance and the mechanical property were investigated by absorbed water ratio, water contact angle and dynamic mechanical measurement.

Study of the physicochemical properties of silica powder and the stability of organic–inorganic hybrid emulsion in the presence of ethanol

The physicochemical properties of silica powder and stability of organic–inorganic hybrid emulsion were investigated. Silica–polymer hybrid latex particles with petal-like morphology were synthesized by emulsion polymerization using a nonionic surfactant OP-10, an anionic surfactant Dowfax 2A1, copolymerization of mixture monomers (MMA–St–BA–AA monomers with molar ratios of 1:1:1.2:0.1), and modified silica powder in the presence of ethanol. The influence of several parameters such as pH values of the suspension, modified silica, ethanol, and monomer on the stability of organic–inorganic hybrid emulsion, latex particle size, and silica content in hybrid polymer was investigated. The experimental results indicate that the amount of surfactant adsorption only was reduced slightly in the presence of ethanol and the displacer effect of ethanol is limited, but ethanol leads to an increase of zeta potential of silica (i.e., a decrease of negative surface charge), and strongly attracts anionic oligomer formed in water onto the surface of silica, thereby promoting the uptake of polymer and monomer from the continuous phase. Silica particles modified by gamma-methacryloxy propyl trimethoxy silane (KH-570) had a proclivity for copolymerization with acrylate monomer due to surface-unsaturated double bond, good compatibility with the polymer due to a significant carbon content that originated from KH-570, low surface silanols group and relatively high zeta potential, thereby improving the SP percentages of hybrid emulsion. Also the weak acid environment leads to an increase of zeta potential of silica and improvement in the stability of hybrid emulsion. Particle formation was predominated by the interaction of the polymer with the silica particles in the earlier stage of polymerization. Optimal conditions were found to obtain a petal-like polymer layer around silica and to preserve the stability of hybrid particles.

A Strategy for Preparation of Anionic Polyurethane/Acrylate Emulsions

In this article we proposed a new strategy for preparation of polyurethane/acrylate (PUA) hybrid emulsions. In the preparation of the polyurethane dispersion, methyl methacrylate (MMA) was used as the reactive solvent to reduce the viscosity of the reaction mixture, and 2-(Dimethylamino)ethyl methacrylate (DMEMA) as the reactive neutralizer. We then let MMA and DMEMA undergo further polymerization to form PUA hybrid emulsions. The morphology of the PUA hybrid emulsions was characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The structures of the waterborne polyurethanes (WPU) and PUA hybrid emulsions were characterized by Fourier transform infrared spectrometer (FTIR) and contact angle measurements.

Thermodynamic Equilibrium Morphology Prediction of Polyurethane/Polyacrylate Composite Latex Particles

AbstractComposite particles were prepared by seeded surfactant‐free batch emulsion polymerization at 80 °C using K2S2O8 as an initiator, and polyurethane aqueous dispersion as seed particles. The acrylate monomers were continuously added into the reactor under a starving condition in the second stage polymerization. The synthesized hybrid emulsions were found to form an inverted core‐shell structure with polyacrylate as the core and with polyurethane as the shell from the observation with a transmission electron microscope. The interfacial tensions between polymer and polymer as well as polymer and water were calculated with a simple method according to harmonic mean equation and used in a mathematical model based on the minimum interfacial energy change principle to predict the equilibrium morphology. The observed particle morphologies were in good agreement with the predicted ones. The surface properties of the dried films formed from polyurethane (PU)/polyacrylate (PA) composite emulsions were also studied by contact angle measurements, showing that the shell part of the composite emulsions is preferentially oriented toward the surface layers of the dried films.

Influence of initiator on synthesis and properties of polyurethane-acrylate hybrid emulsion

The prepolymer polyurethanes (PUs) based on isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG), 1,4-butanediol (BDO) and dimethylopropionic acid (DMPA) were synthesized at 75–80 °C for 7–8 hours, using dibutyltin dilauate (DBTDL) as catalyzer, and polyurethane-acrylate hybrid emulsion was prepared after methyl methacrylate (MMA) was polymerized, using potassium persulfate and azobisisobutyronitrile (AIBN) as initiator, respectively. The influences of these factors such as the kind of initiator, the feed method of initiator and the addition of initiator on properties of polyurethane-acrylate were studied. The FTIR and GPC of aqueous polyurethane were analyzed. The FTIR spectra show that the degree of microphase-separate between the soft segments and rigid segments is high. The analysis of molecular weights stated that molecular weights increased most significantly after amine was added. The experimental results reveal that the appearance of emulsion is excellent, the film is harder and the water absorption radio of the film is less when oil-solubility AIBN is used as initiator. The semi-continuous can increase the molecular weight of polymer and the optimum amount of the initiator was 3% for MMA.

Poly(vinyl chloride) composite emulsion resins modified by polyurethane

An ionomer-type of polyurethane (PU) emulsion was prepared from toluene diisocyanate (TDI), polypropylene glycol (PPG) and dimethylol propionic acid (DMPA) following a self-emulsification process. The modified poly(vinyl chloride) (PVC) emulsion resin was obtained by in situ emulsion copolymerization using the PU as seeds in an autoclave. The effects of PU molecular weight on the mechanical properties and thermal stability of the PU/PVC materials were investigated. The composite latex particles and composite materials were determined and characterized using a laser particle size analyzer, transmission electron microscopy or scanning electron microscopy. The study results showed that the PU/PVC hybrid emulsion particles possess a core/shell structure. When the general mechanical properties of the composite materials increase, the thermal stabilities decrease a little. The tough fractures on the surface of the PU/PVC composite sample following impact are quite obvious.

Developing a hybrid emulsion polymerization system to synthesize Fe3O4/polystyrene latexes with narrow size distribution and high magnetite content

AbstractA hybrid emulsion polymerization was formulated for synthesizing Fe3O4/polystyrene composite latex. This system, containing binary droplets that are magnetic (Mag)‐droplets with a diameter of 100–200 nm and styrene (St)‐droplets with a diameter of 3–4 μm, was obtained by mixing Mag‐miniemulsion and St‐macroemulsion. With extremely low surfactants concentration (≪critical micelle concentration, CMC), the nucleated loci are selectively controlled in the Mag‐droplets, as the result of smaller droplet size and larger surface ratio. Both water‐soluble potassium persulfate (KPS) and oil‐soluble 2,2′‐azobis(2‐isobutyronitrile) was adopted to initiate the polymerization. In the presence of KPS, magnetic polystyrene latices with particles size of 60–200 nm, narrow size distribution, and high magnetite content (86 wt % measured by TGA) were attained successfully. The synthesized magnetic Fe3O4/polystyrene latices assembled into well‐ordered hexagonal structure in the surface of a carbon supported copper grid. The influence of various parameters on various aspects of the as‐synthesized Fe3O4/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag‐miniemulsion and St‐macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5285–5295, 2007

A new core–shell type fluorinated acrylic and siliconated polyurethane hybrid emulsion

A novel core–shell type fluorinated acrylic and siliconated polyurethane (FSiPUA) hybrid emulsion was prepared by seeded emulsion polymerization using siliconated polyurethane (SiPU) as a seed and forming the structure with SiPU as a shell and the copolymer of butyl acrylate (BA) with 2,2,2-trifluoroethylmethacrylate (TFEMA) as a core. SiPU was synthesized using isophorone diisocyanate (IPDI), polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), dihydroxybutyl-terminated polydimethylsiloxane (PDMS), dimethylol propionic acid (DMPA), 1,6-hexanediol (HDO) and triethylamine (TEA). The contents of siloxane and fluorine were determined according to the feed ratio. Fourier transform infrared spectroscopy (FTIR) was used to identify the chain structure of SiPU and FSiPUA. Investigation of transmission electron microscopy (TEM) confirmed the core–shell structure of FSiPUA emulsion and gave the particle size at about 50 nm. The measurement results of water contact angles and the solvent absorptions in water and n-octane for cured films showed that the water and the oil repellency for FSiPUA had been improved significantly with a suitable content of fluorine and siloxane.

Sol−Gel Reaction in Acrylic Polymer Emulsions: The Effect of Particle Surface Charge

Acrylic polymer-silica hybrid emulsions were synthesized from both anionic and cationic polymer emulsions by simple post-addition of tetraethoxysilane as a silica precursor. Solvent resistance of the films from the hybrid emulsions and the zeta-potential of the hybrid emulsions suggested the different forms of silica components in each hybrid emulsion. Thermal gravimetric analysis, 29Si NMR measurements, and transmission electron microscope observations revealed that the hybrid emulsion from the anionic polymer emulsion was a mixture of anionic polymer particles and homogeneously dissolved silicate oligomer-polymer. On the contrary, the hybrid emulsion from cationic polymer emulsion consisted of polymer core-silica shell particles. The electrostatic interaction between the cationic polymer particle surface and the silicate would be responsible for the accumulation of the silicate onto the particle surface, leading to the silica shell layer formation. The sol-gel condensation reaction of silicate in the acidic emulsion phase was revealed to be controllable by the surface charge of the coexisting particles.

Acrylic polymer/silica organic–inorganic hybrid emulsions for coating materials: Role of the silane coupling agent

AbstractAcrylic polymer/silica organic–inorganic hybrid emulsions were synthesized by a simple method, that is, a conventional emulsion polymerization and subsequent sol–gel process, to provide water‐based coating materials. The acrylic polymer emulsions contained a silane coupling agent monomer, such as methacryloxypropyltriethoxysilane, to form highly solvent‐resistant hybrid films. On the other hand, the hybrid films from the surface‐modified polymer emulsions, in which the silane coupling agent was located only on the surface of the polymer particles and the particle core was not crosslinked, did not exhibit high solvent resistance. A honeycomblike array structure, which was derived from the polymer particles (diameter ≈ 50 nm) and the silica domain, on the hybrid film surfaces was observed by atomic force microscopy. The crosslinked core part and silane coupling agent containing the shell part of the polymer particles played important roles in attaining high solvent resistance. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4736–4742, 2006

Properties of acrylic–polyurethane hybrid emulsions synthesized by the semibatch emulsion copolymerization of acrylates using different polyurethane particles

AbstractAqueous acrylic–polyurethane hybrid emulsions were prepared by the semibatch emulsion copolymerization of methyl methacrylate and butyl acrylate in the presence of eight polyurethane dispersions. The polyurethane dispersions were synthesized with isophorone diisocyanate, 1000 and 2000 molecular weight polyester polyols, 1000 molecular weight polyether polyol, butanediol, and dimethylol propionic acid. Acrylic monomers were added in the monomer emulsion feed. We studied the effect of the use of different polyurethane seed particles and the effect of different weight ratios of methyl methacrylate to butyl acrylate on the emulsion properties, microphase structure, and mechanical properties of hybrid films. The average particle size and distribution were determined by photon correlation spectroscopy. The rheological properties of polyurethane dispersions and hybrid emulsions were tested under destructive conditions by an examination of flow curves and under nondestructive conditions of oscillatory shear in a range of linear viscoelastic responses. Differential scanning calorimetry was performed to characterize the thermal‐response properties of polymeric films. The relative average molecular weights were determined by gel permeation chromatography. The interactions between the acrylic and polyurethane components in hybrid particles and particle structure were studied with infrared spectroscopy and nuclear magnetic resonance spectroscopy. Mechanical properties such as the Koenig hardness, tensile strength, elongation at break, and Young's modulus were measured. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4050–4069, 2005