Effect of composition on aqueous polyurethane dispersions derived from polycarbonatediols

Aqueous polyurethane dispersions derived from isophorone diisocyanate, various polycarbonatediols of different molecular weights, and dimethylol butyric acid were prepared by a dispersing procedure modified to enhance molecular weight. Particle size, average molecular weight, and tensile properties were determined. The molar ratio of reactants affected the properties of the polyurethane dispersions significantly, with the trends described as the effects of their ionic group and polycarbonatediol soft‐segment contents. The molecular weight of the polycarbonatediols also significantly affected the particle size of the aqueous polyurethane dispersions and the film properties. As the molecular weight of the polycarbonatediols decreased, the particle size of the aqueous polyurethane dispersions decreased, and the moduli of the cast films increased, as expected. However, the tensile strength of the cast films decreased as the molecular weight of the polycarbonatediols decreased because of the decrease in elongation at break. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4419–4424, 2006     

聚氨酯水分散体涂料

概述了聚氨酯水分散性的性能与结构的关系。介绍了几种不同灰型的聚氨酯水分散体,及其组成,制备和应用等。     

聚氨酯-丙烯酸酯水分散体系稳定性研究

通过PUA水分散液一些物理性质 ,如 ζ电位、临界聚沉值 (C .C .C)、pH值、粒径及密度等的测量 ,用DLVO理论分析了聚氨酯 丙烯酸酯水分散体系的稳定性 ,并与实验测定的水分散液在不同条件下的稳定性相对照。结果表明 :用DLVO理论分析具有不同羧基 (—COOH)含量的PUA水分散液的稳定性时所得结果 ,与实验结果较吻合 ;而用该理论分析不同丙烯酸酯 (PA)含量的PUA水分散液时 ,与实验结果有偏差 ,可能与DLVO理论假设粒子形态为球形有关     

Synthesis of a hydrosoluble reversible addition-fragmentation chain transfer agent and application in the preparation of micro/nano-polyacrylamide gel dispersions

A hydrosoluble reversible addition-fragmentation chain transfer (RAFT) agent named S-(2-propionic acid)-S′-(2-methylpropionic acid) trithiocarbonate (PAMPATTC) is successfully synthesized. Then the micro/nano-polyacrylamide gel dispersions are prepared via one-pot RAFT polymerization in water to solve the problems of complicated preparation process and particle size control of common profile-controlling and flooding agents. The structure of the RAFT agent is characterized and confirmed by fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (¹H-NMR). The effects of different reaction conditions on the properties of polyacrylamide gel dispersions are studied. The polymer dispersity index (PDI) of the polyacrylamide gel dispersions is tested by aqueous gel permeation chromatography, confirming the activity characteristics of RAFT polymerization. The rheological characteristics of the polyacrylamide gel dispersions and liner polyacrylamide are characterized. Compared with the liner polyacrylamide at similar viscosities, it is confirmed that the polyacrylamide gel dispersions were closer to Newtonian fluid, especially at high shear rates and the increasing amount of RAFT agent. The viscoelasticity tests under frequency scanning further confirm that the polyacrylamide gel dispersions are successfully synthesized via aqueous RAFT polymerization. The particle sizes are measured to show that the particle size of the polyacrylamide gel dispersions is micro/nano-scale. The micromorphology of polyacrylamide gel dispersions is determined to indicate the irregular spherical structure, confirming that the micro-particles are indeed formed by the aggregation of nano-particles.     

Anionic waterborne polyurethane dispersions based on hydroxyl‐terminated polybutadiene and poly(propylene glycol): Synthesis and characterization

Nonpolluting systems based on anionic polyurethane aqueous dispersions were obtained. The prepolymer based on hydroxyl‐terminated polybutadiene (HTPB), isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG), and dimethylolpropionic acid (DMPA) were synthesized in bulk. After neutralization with triethylamine (TEA), the anionomer prepolymer was dispersed in water, followed by a chain‐extension reaction with ethylenediamine (EDA). The prepolymers were characterized by Fourier transform infrared spectrometry (FTIR) and the average particle size of the aqueous dispersions was determined by laser light scattering (LLS). The mechanical behavior of polyurethane‐cast films and the adhesive properties of the aqueous dispersions as coatings for wood were evaluated. It was observed that an increase in the HTPB content provoked an increase in the viscosity and in the particle size of the dispersions. The tensile strength and the modulus values of the films and the adhesiveness of the coatings in wood were also increased by increasing the HTPB content. On the other hand, the elongation of the polyurethane‐cast films and the tackness of the surface coatings decreased as the HTPB was increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 566–572, 2001     

Synthesis of a water-soluble chain transfer agent and its application in gel dispersions

Pre-crosslinked gel particles, colloidal dispersion gels, and polymer microspheres are often used as profile-controlling and flooding agents to displace residual crude oil from formations. The preparation process of these profile-controlling and flooding agents is complicated. In order to simplify the preparation steps, a water-soluble chain transfer (RAFT) agent, S,S′-bis(2-propionic acid) trithiocarbonate (PATTC), was synthesized, and then, hydrogel dispersions were prepared by one-pot RAFT polymerization. The structure of PATTC was confirmed by infrared spectroscopy and nuclear magnetic resonance. The effects of reaction conditions on the viscosity and viscosity-average molecular weight of hydrogel dispersions were explored, the rheology, viscoelasticity, particle size, temperature responsiveness, and salinity responsiveness of hydrogel dispersions were measured, and the seepage properties of hydrogel dispersions in porous medium were analyzed. The results show that at higher shear rates, the polyacrylamide gel dispersions exhibited Newtonian fluid characteristics. Viscoelasticity tests further confirmed that the polyacrylamide gel dispersions were successfully synthesized. The particle size of the hydrogel dispersions is 1–75 μm, its viscosity is less affected by temperature and salinity, and its residual resistance coefficient is higher than that of the polyacrylamide solution under similar apparent viscosity.     

Effect of ionic content,solid content,degree of neutralization,and chain extension on aqueous polyurethane dispersions prepared by prepolymer method

There are many variables in the preparation of aqueous polyurethane (PU) dispersions. Carboxylic acid content, solid content, degree of pre/postneutralization of the carboxylic acids, and chain extension all impact dispersion particle size, viscosity, pH, molecular weights, and glass transition temperature. This study evaluated the impact of these variables on a given PU dispersion formulation prepared from isophorone diisocyanate, an aliphatic polyester polyol, dimethylol propionic acid, and hexamethylene diamine with triethyl amine as the neutralizing base and N‐methyl pyrrolidone as the cosolvent. Changes in carboxylic acid content, degree of preneutralization, and chain extension were found to have the expected impacts on dispersions properties. Increased ionic content in the dispersion step led to lower particle size and higher viscosity, increased chain extension with its concurrent increase in molecular improved subsequent film properties. Surprising results were obtained by varying the amount of postneutralization and from increased solids content at the time of dispersion. Unexpectedly, both of these variations led to much higher dispersion viscosities and particle size in solution. To have these changes take place, it is theorized that there is a major change in solution morphology caused by these modifications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2514–2520, 2005     

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     

Polyurethane ionomer dispersions from a blocked aromatic‐diisocyanate prepolymer

Aqueous anionic blocked aromatic polyurethane prepolymers were synthesized by a prepolymer mixing process and their dispersions were obtained by adding water to the blocked prepolymer solutions. A series of prepolymers were prepared by using toluene 2,4‐diisocyanate, 4,4′‐diphenylmethane diisocyanate, polytetramethylene glycol, dimethylol propionic acid, methyl ethyl ketoxime and ε‐caprolactam. The aqueous dispersions were characterized by Fourier‐transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis. The particle sizes, viscosities, pH and storage stabilities of the dispersions were studied and compared. Some mechanical properties of the cast films obtained from the aqueous dispersions and the adhesive properties of the dispersions were also evaluated. Copyright © 2004 Society of Chemical Industry     

Sedimentation stability of aqueous dispersions of nanodiamond agglomerates

The electric conductivity and sedimentation stability of aqueous dispersions of nanodiamond agglomerates are studied. The properties and stability of dispersions were shown to be significantly affected by the pretreatment of particles. The particle size distribution was determined by means of optical microscopy. The sedimentation kinetics of nanodiamond particles in aqueous solutions was studied. The sedimentation kinetic curves showed two sections of fast and slow sedimentation. The obtained results are necessary to develop the technology of nanoporous carriers in analytical and preparative chromatography     

Preparation,mechanical properties of waterborne polyurethane and crosslinked polyurethane‐acrylate composite

The waterborne polyurethane (PU) prepolymer was first prepared based on isophorone diisocyanate, polyether polyol (NJ‐210), dimethylol propionic acid (DMPA), and hydroxyethyl methyl acrylate via in situ method. The crosslinked waterborne polyurethane‐acrylate (PUA) dispersions were prepared with the different functional crosslinkers. The chemical structures, optical transparency, and thermal properties of PU and PUA were confirmed by Fourier transform infrared spectrometry, ultraviolet–visible spectrophotometry, and differential scanning calorimetry. Some physical properties of the aqueous dispersions such as viscosity, particle size, and surface tension were measured. Some mechanical performances and solvent resistance of PUA films were systemically investigated. The experimental results showed that the particle sizes of the crosslinked PUA aqueous dispersions were larger than the PU and increased from 57.3 to 254.4 nm. When the ratios of BA/St, BA/TPGDA, and BA/TMPTA were 70/30, PUA films exhibited excellent comprehensive mechanical properties. The tensile strength and elongation at break of the film were 2.17 MPa and 197.19%. When the ratio of BA/St was 30/70, the film had excellent water resistance and was only 6.47%. The obtained PUA composites have great potential application such as coatings, leather finishing, adhesives, sealants, plastic coatings, and wood finishes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

阴离子水性聚氨酯内乳化剂的研究进展

综述了国内外多种羧酸型乳化剂的制备方法,以及乳化剂对阴离子水性聚氨酯的合成工艺、引入离子基团的中和方式、中和度、亲水基团含量、扩链反应的温度及乳化温度对乳液性能的影响。     

Utilization of aerosolspectroscopy for determination of the particle size distribution of aqueous dispersions in the submicroscopic range

A recently developed aerosolspectrometer offers a new method for particle size analysis of aqueous dispersions in the submicroscopic range. This technique combines simple sample preparation and quick measurement with excellent resolution. The usefulness of the method is demonstrated by some typical examples.     

PU/BA-HEMA互穿网络型聚合物的合成及性能

以异佛尔酮二异氰酸酯（IPDI）、二羟甲基丙酸（DMPA）为硬段,聚醚多元醇（N220）为软段,以丙烯酸丁酯（BA）和甲基丙烯酸羟乙酯（HEMA）改性,制备了水性聚氨酯（PU）分散液,测定了水分散液及其膜的物理性能和力学性能。结果表明,与未改性的PU水分散液相比,改性聚氨酯水分散液的粒径均有所增大,表面张力减小,力学性能和硬度提高。HEMA 的引入,形成了具有化学交联的核-壳互穿网络结构的聚合物,说明改性材料中分子链硬段与PA分子链具有较高的相容性。     

Polyelectrolyte complex between chitosan and poly(2-acryloylamido-2-methylpropanesulfonic acid)

Summary A new polyelectrolyte complex between chitosan and poly(2-acryloylamido-2-methylpropanesulfonic acid) (PAMPS) was prepared by mixing aqueous solutions of its components or by free radical polymerization on chitosan template. The complex formation was sensitive to the ionic strength of the medium. The complex was stable in acidic and neutral medium and dissociated at pH > 8. Its composition did not depend on pH values of the medium and the way of preparation. The mixing dilute aqueous solutions of chitosan and PAMPS resulted in the formation of nanoparticles with mean particle diameter 250 nm and monomodal distribution. Received: 16 May 1999/Revised version: 18 June 1999/Accepted: 18 June 1999     

Preparation and Characterization of Chitosan Coated Surgical Gauze Using Potassium Persulfate as Thermal Initiator

Chitosan powder was extracted from prawn shell via chitin formation by chemical treatment. Chitosan solution (2 wt.%) was prepared in aqueous solution containing ethanoic acid (2 wt.%) along with varying amounts of potassium persulphate as thermal initiator (10 to 50 mg). Surgical gauze was immersed in the chitosan solution for 10–45 min. Coating was carried out at 70–110°C and heating time varied from 30–180 min. Chitosan uptake and the mechanical properties of the chitosan coated surgical gauze, such as tensile strength (TS) and elongation at break (Eb), were measured. Soaking time, curing time, and curing temperature of the surgical gauze were optimized for the preparation of coated gauze over chitosan uptake and mechanical properties. Surgical gauze soaked for 20 min at 90°C for 120 min of curing showed the highest chitosan uptake and TS (9 MPa). Soil burial tests revealed that coated gauze became twisted and almost degraded within 6 weeks of ageing. Water uptake properties of the coated gauze were monitored. Scanning electron microscopic analysis of the surface of the coated gauze found that the coating of chitosan became brittle with the use of higher amounts (50 mg) of thermal initiator.     

杂化型水性聚氨酯技术进展

简述丙烯酸酯杂化改性聚氨酯缘由,介绍几种目前常用的制备方法,并略谈杂化物的优异性能。     

Rheological properties of hydrolyzed polyacrylonitrile-grafted cellulose

The rheological properties of aqueous dispersions of hydrolyzed polyacrylonitrile-grafted cellulose (H-CPAN) have been investigated. The experimental results are consistent with the idea that the elementary particle is a rigid cellulose protofibril stabilized in suspension by associated polyelectrolyte side chains (polyacrylamide–polyacrylic acid copolymer grafts). The behavior of intrinsic viscosity with electrolyte concentration, the concentration depependence and shear dependence of the viscosity and of the steady-state and dynamic shear moduli are qualitatively explained on this basis.     

Adsorption behavior of reactive dyes from aqueous solutions on chitosan

The capability of the use of chitosan for removing vinyl sulfone and chlorotriazine reactive dyes from aqueous solutions was examined, including equilibrium and dynamic studies. Experiments were performed as a function of dye concentration, and the amount and particle size of chitosan. It was shown that the adsorption capacities of chitosan were comparatively high for the three investigated dyes. The equilibrium data could be best fitted by the Redlich–Peterson equation over the entire concentration range (50–500 g m⁻³). A comparison of the adsorption capacity among such adsorbents as chitin and powdered activated carbon was made. Two rate parameters were finally obtained to describe the adsorption process on a quantitative basis. These parameters could be well correlated to the amount and particle size of dry chitosan. ©1997 SCI     

The influence of the ionic concentration, concentration of the polymer, degree of neutralization and chain extension on aqueous polyurethane dispersions prepared by the acetone process

There are many variables in the preparation of aqueous polyurethane (PU) dispersions. Chemical and compositional variables such as carboxylic acid concentration, concentration of the polymer, degree of pre/post-neutralization of the carboxylic acids and chain extension that all impact solution properties such as particle size and viscosity. Another variable is the method by which the dispersion is prepared; two primary methods are currently employed in industrial manufacture, the prepolymer mixing process and the acetone process. This study evaluates the impact of the chemical variables on a given PU dispersion formulation prepared by the acetone process. Changes in carboxylic acid concentration, degree of pre/post-neutralization and chain extension were found to have the expected impacts on dispersion solution properties. Increased ionic concentration, and degree of pre-neutralization led to lower particle size and higher viscosity, increased degree of chain extension led to larger particle size and lower viscosity, increased post-neutralization increased both particle size and viscosity, and increased concentration of the polymer led to a viscosity increase without any change in particle size.