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.     

Preparation and Properties of Water-borne Polyurethanes

Following a prepolymer mixing process, polyurethane (PU) anionomer dispersions were prepared from polyethylene adipate glycol (PEA), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI) and dimethylol propionic acid (DMPA) as a potential ionic centre. Effects of prepolymer molecular weight, PEA molecular weight, hard segment content, DMPA content, degree of neutralization and mixed diisocyanates have been studied in terms of particle size and viscosity of emulsion, and surface, mechanical and dynamic mechanical properties of the emulsion-cast films. Particle size decreased and emulsion viscosity increased with increase in prepolymer molecular weight and PEA molecular weight, DMPA content, the degree of neutralization and IPDI content in mixed isocyanate systems. The decrease in particle size was due to increased chain flexibility and/or hydrophilicity of the PU. The mechanical and dynamic mechanical properties of the PU ionomer dispersions were interpreted in terms of soft segment–hard segment phase separations, hard segment content, chain flexibility and coulombic forces. © of SCI.     

Dual-curing of anionic aqueous-based polyurethanes at ambient temperature

Polyurethane (PU) prepolymers are prepared by a polyaddition of isophorone diisocyanate, polypropylene glycol-1000, and 2,2-dimethylolpropanic acid. The anionic aqueous-based PU dispersions are derived from a water dispersion process of these NCO-terminated PU prepolymers together with a neutralization and a chain extension. They have both terminal amino and pendent carboxylic groups which are potentially reactive sites toward a di-functional epoxy and a tri- or di-aziridinyl compound of a dual-curing PU system, respectively. The stabilities of the resulting PU dispersions on zeta potential and particle size distributions are investigated. The improvements on mechanical, physical, and thermal properties of these dual-cured PU systems are also evaluated. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1661–1671, 1998     

Stability and properties of waterborne polyurethane/clay nanocomposite dispersions

Factors that can affect the stability of waterborne polyurethane (WBPU)/clay nanocomposite dispersions are reported. It is suggested that the dispersion stability depends on the carboxyl acid salt content, clay content, sonication (mechanical forces), and clay surface structure. It was observed that the dispersion stability increased with increasing carboxyl acid salt content after applying sonication (mechanical forces) in clay with OH groups (Cloisite 30B) up to 23.58 mol% DMPA. Encapsulated (WBPU20-30B4-M and WBPU23-30B5-M) clay in PU particles was formed using the above combination. The dispersion with clay encapsulated in PU particles had the longest storage time of all of the dispersions. The zeta potential, particle size, particle size distribution, and viscosity of the dispersions also depend on carboxyl acid salt content, clay content, sonication (mechanical forces), and clay surface structure.     

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.     

Waterborne hybrid alkyd–acrylic dispersion: Optimization of the composition using mixture experimental designs

VOC-free waterborne hybrid alkyd–acrylic (50/50 wt/wt) dispersions were synthesized by melt condensation reactions between acrylic pre-polymers bearing carboxylic groups and medium-oil alkyd resins, followed by a self-emulsification through the neutralization of the carboxylic groups by an aqueous ammonia solution. A mixture experimental design was used to investigate how formulation components of the hybrid alkyd–acrylic resin affect the properties of the hybrid dispersion in terms of the viscosity of the dispersion, particle size, hydrolytic stability, and coating performance, namely gloss and film hardness. It was found that the content of ionizable monomers is the dominant factor controlling the particle size. This latter was shown to meaningfully affect the gloss of the coating after drying. The viscosity of the dispersion was mainly governed by the content of the soybean oil fatty acid which also controlled the hardness of the coating film after drying. An optimal composition that fits the requirement of paint formulation in terms of particle size, viscosity, hardness, and gloss was defined on the basis of the results of the mixture experimental design.     

Study on high‐solid content Si/PU polyurethane dispersion with PES/PPG composite soft segment

A polyol consists of silicone chains and epoxy acrylate structures, referred to as silicon polyether (PES), was used to prepare crosslinked Si/PU dispersions. Both PES and propylene oxide glycol (PPG) were mixed as soft segments. The effects weight ratios of PES to PPG on properties of the resultant polyurethane dispersions were studied. Morphology and properties of the Si/PU dispersions were characterized by particle size, transmission electron microscopy (TEM), and viscometer. It is shown that the Si/PU dispersions possessed wider particle size distribution and higher average particles diameter because of the use of PES, which contains crosslinked silicone side chains. The Si/PU dispersions have higher solid content as compared to the conventional water‐based polyurethane, because of the volume fraction ratio of bigger particle to small particle from the Si/PU dispersions. As increasing weight ratio of PES to PPG, the solid content of the Si/PU dispersions increased firstly, and then decreased. When the ratio ranges from 4 : 10 to 5 : 10, solid content of the Si/PU dispersions is up to 55%. It was also noticed that apparent viscosity of the Si/PU dispersions decreased with increasing PES to PPG ratio. In the Si/PU dispersions, solid content was increased and viscosity was decreased by the use of PES. Therefore, PES is a potential compound for the application of PU dispersions. In addition, stability of the crosslinked Si/PU dispersions decreases slightly at high‐ and low‐temperature; however, which can meet the basical requirements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Application of statistical experimental strategies to the process optimization of waterborne polyurethane

A modified acetone process for the preparation of aqueous polyurethane (PU) dispersion is investigated. PU dispersions were prepared by polyaddition of isophorone diisocyanate (IPDI) to poly(tetramethylene ether glycol) (PTMG) and dimethylolpropionic acid (DMPA), followed by neutralization of pendant COOH groups with triethylamine (TEA). The resulting prepolymer chain was then extended through reaction with an ethylenediamine (EDA) derivative bearing sulfonate groups. The effect of such preparation conditions as catalyst (dibutyltin dilaurate, DBTDL) concentration, the acetone/PU ratio, phase-inversion temperature, agitation rate, and water-addition rate on the average particle size of aqueous PU anionomer dispersions is systematically studied using fractional factorial design and response surface methodology. Fractional factorial analysis indicates that the effects of the acetone/PU ratio, phase-inversion temperature, water-addition rate as well as the two factor interactions of DBTDL concentration and phase-inversion temperature, of the acetone/PU ratio and phase-inversion temperature, and of acetone/PU ratio and agitation rate are the key variables influencing average particle size of PU dispersions. Empirical models for average particle size are fitted and plotted using central composite experimental design as contour diagrams in order to facilitate examination of the average particle size results. The results show that for a 100 g PU anionomer containing 0.311 wt % COOH and 1.51 wt % SO₃H groups, a minimum number-average particle size of the dispersion ～ 25 nm can be obtained under an acetone/PU ratio, water-addition rate, phase-inversion temperature, catalyst concentration, and agitation rate of 3.65, 2 mL/min, 50°C, 150 ppm and 350 rpm, respectively.     

水性聚氨酯链段序列分布对乳液固含及性能的影响

通过改变预聚加料顺序,采用"拼接软段"的方法,合成了一系列总体成分相同而链段分布不同的水性聚氨酯乳液。着重研究了乳化过程相反转完成时乳液的固含变化,进而对乳液的黏度、粒径、分子量以及乳液表干速度进行测试,藉此分析链段分布对乳液粒子结构和性质的影响。结果表明,适度地改变软硬段在聚氨酯主链上的相对分布,能有效提升水性聚氨酯乳液的固体含量,其机理是增加软硬段平均长度,使它们更容易各自聚集,因此乳化时乳液粒径增大,而且羧基更多迁移到粒子的壳层,使得粒子内部水分较少,表干速度大大加快。     

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     

Anionomeric waterborne poly(urethane semicarbazide) dispersions and their adhesive properties

Aqueous polyurethane dispersions were prepared from isocyanate‐terminated ionic polyurethane prepolymers by chain extension with dihydrazides. These water‐borne dispersions had excellent adhesive properties and were used to bond leather and canvas. The base polymers were varied with respect to (1) the ionic content with the same chain extender and (2) the nature of the chain extender with the ionic content kept constant. Studies on the particle size and viscosity revealed that the ionic content had an influence on the aforementioned properties: the particle size decreased and the viscosity increased with increasing ionic content. The polarity of the films cast from the dispersions were determined with contact‐angle measurements: hydrophilic character was exhibited by all the compositions. X‐ray studies revealed that the increase in the ionic content led to increasing intensities of the diffraction peaks due to increased secondary forces of bonding. The tensile strength measurements showed that the films were highly elastomeric and had good mechanical strength, which varied with the composition. A shear strength and peel strength analysis of specimens obtained through the bonding of leather to leather, leather to canvas, and canvas to canvas revealed that the waterborne dispersions were excellent adhesives for bonding leather surfaces. Thus, a very efficient, ecofriendly waterborne dispersion of polyurethane that could find applications in bonding leather in the footwear industry was prepared successfully. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of isocyanic acid,m‐phenylenediiso‐propylidene based poly(urethane‐urea) dispersions containing different amount of 2,2‐Bis(hydroxyl methyl)propionic acid

Isocyanic acid, m‐phenylenediiso‐propylidene (m‐TMXDI)‐based anionic poly(urethane‐urea) dispersions were prepared by the prepolymer mixing process. The equivalent ratio of NCO/OH was kept constant at 1.8, while 2,2‐bis(hydroxyl methyl) propionic acid (DMPA) used was varied from 3 to 10 wt %. The colloidal stability of poly(urethane‐urea) dispersions arose entirely from the presence of ionized carboxylic acid groups. The chemical structure of poly(urethane‐urea) dispersions with various amount of DMPA were identified by FTIR and ¹³C NMR analysis. The test results showed that the hydrophilicity of poly(urethane‐urea) dispersions were increased with increase in DMPA content. The degree of chain extension was much lower than the values predicted theoretically due to the side reaction of a small amount of hydrophilic isocyanate‐terminated prepolymer with water. The average particle size of poly(urethane‐urea) dispersions were decreased with an increase in DMPA content, and this lead to an increase in viscosity. Also, the thermal degradation behavior were measured and was shown that the initial degradation temperature shifted to lower temperature with an increase in DMPA content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5737–5746, 2006     

Introduction of covalently bonded phosphorus into aqueous‐based polyurethane system via postcuring reaction

Anionic aqueous‐based polyurethane (PU) dispersions were derived from a water dispersion process of carboxylic groups containing PU prepolymers together with a neutralization and a chain extension. These PU prepolymers were prepared from a conventional polyaddition of isophorone diisocyanate, polypropylene glycol‐1000, and dimethylolpropanic acid. A covalently bonded phosphorus was introduced into PU by a phosporus‐containing curing agent. A series of phosphorus and multi‐aziridinyl groups containing curing agents were synthesized for this purpose. Each of them served in a dual‐function capacity as a postcuring agent for the anionic aqueous‐based PU system. The resulting postcured PU exhibited improvements in its mechanical, physical, and thermal properties; furthermore, postcured PU synergistic flame inhibition was also observed due to the presence of nitrogen and phosphorus content in the process. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2499–2509, 1999     

Study of ionic/nonionic polyurethane dispersions with high solid content and low viscosity using a complex hydrophilic chain-extending agent

An ionic/nonionic polyurethane dispersion with high solid content and low viscosity with a complex hydrophilic chain-extending agent was prepared using isophorone diisocyanate as a hard segment and propylene oxide glycol as a soft segment. The complex hydrophilic chain-extending agent consisted of DPSA and BDSA. The effects of the molar ratio of DPSA/BDSA on the properties of the resultant polyurethane dispersions were studied. The morphologies and properties of the ionic/nonionic PU dispersions were examined using particle-size, TEM, and viscosity analyses. It was found that the ionic/nonionic dispersions possessed wide particle-size distributions due to the addition of the complex hydrophilic chain-extending agent. The ionic/nonionic PU dispersions possessed higher solid content than conventional WPU dispersions because the number and volume percentage of the large particles and small particles of the ionic/nonionic dispersions met the requirements for high solid content. It was observed that the solid content of the ionic/nonionic dispersion increased and then decreased with an increasing molar ratio of DPSA/BDSA. When the ratio ranged from 4:10 to 5:10, the solid content of the ionic/nonionic PU dispersion reached up to 55%. It was also noticed that the apparent viscosity of the ionic/nonionic polyurethane dispersion decreased with an increasing molar ratio of DPSA/BDSA. The complex hydrophilic chain-extending agent consisting of DPSA and BDSA enhanced the solid content and decreased the viscosity of the ionic/nonionic dispersions, which are very important for improving the properties and expanding the applications of PU dispersions. In addition, the ionic/nonionic polyurethane dispersion had good electrolyte-resistance properties, stability at both high and low temperatures, and storage stability.     

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     

FTIR, 1H‐NMR spectra,and thermal characterization of water‐based polyurethane/acrylic hybrids

Polyurethane (PU) polymer was synthesized following a prepolymer mixing process, by polyaddition of isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG), 2‐hydroxyethyl methacrylate (HEMA), and 2,2‐bis(hydroxymethyl)propionic acid (DMPA). The PU anionomer having 2‐ethoxymethacrylate terminal groups was dispersed in water by prior neutralization of carboxylic acid groups of DMPA with triethylamine (TEA), chain extended with hydrazine (HZM) in water and a dispersion polymerization with methyl methacrylate/n‐butyl acrylate/acrylic acid mixture was performed. The above polymerization reactions lead to the formation of PU/acrylic hybrids having a chemical bond between PU and acrylic moieties. Acrylic content was varied from 0 to 50 wt % and samples were purified to eliminate oligomers and impurities before characterization. The FTIR and ¹H‐NMR spectra of these purified hybrid samples were obtained and bands and peaks assignments were discussed. Thermal properties (DSC and TGA) were also discussed. Breaking hydrogen bonds is the main reason for changes in properties with increasing acrylic content. Particle size data of dispersions is also presented and discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

乙二胺扩链剂对水性聚氨酯性能的影响

以聚醚220、异佛尔酮二异氰酸酯(IPDI)为主要原料,二羟甲基丙酸(DMPA)为亲水性扩链剂,丁二醇(BD)和乙二胺(EA)为小分子扩链剂,按不同配比合成了系列水性聚氨酯分散体。主要考察了乙二胺扩链剂用量对水性聚氨酯乳液的稳定性、乳液粒径、粘度以及膜吸水性和力学性能的影响。结果表明,随乙二胺扩链剂用量的增加,乳液粒径增大、分散稳定性变差、粘度减小、胶膜的拉伸强度增加、断裂伸长率减小、耐溶剂性增加、吸水率变化不明显、硬段相Tg升高,软硬段相分离程度增加。胶膜的ATR红外表现为PPG类聚醚型聚氨酯典型的红外光谱。     

乙二胺后扩链TDI型聚氨酯水分散体的过程

以甲苯二异氰酸酯（TDI）、聚氧化丙烯二醇和二羟甲基丙酸等为主要原料制备了聚氨酯水分散体,研究了水、扩链温度、原料的-NCO/-OH摩尔比及扩链比对乙二胺（EDA）后扩链TDI型聚氨酯水分散体过程的影响。FT-IR测试表明,分散体中的H₂O可通过与聚氨酯中残留异氰酸酯基团（-NCO）的竞争反应影响EDA的后扩链过程。分子量及粒径与zeta电位测试表明,H₂O扩链导致分散体失稳;低扩链比时,H₂O对EDA的后扩链过程影响明显,但高扩链比时,后扩链聚氨酯的分子量降低;扩链温度升高,经EDA后扩链聚氨酯的分子量降低,而分散体粒径增大。当原料的-NCO/-OH摩尔比为1.20、扩链温度为30℃、扩链比为60%时,可有效降低H₂O对EDA后扩链聚氨酯过程的影响。     

丙烯酸树脂改性水性聚氨酯的结构与性能研究

采用丙烯酸树脂对水性聚氨酯进行改性，得到了共混改性（PU／PA）、共聚改性（PUA’）、接枝改性（PUA）3种丙烯酸改性水性聚氨酯聚合物。通过对改性聚氨酯乳液的激光粒度分析，乳胶膜的红外光谱、热分析、透明性、耐化学性及扫描电镜进行分析，结果表明：改性后的水性聚氨酯，各项性能均有不同程度的提高。在机械共混聚合物PU／PA体系中，聚氨酯分子链和丙烯酸树脂分子链间具有一定的相容性及共混性；在共聚反应聚合物PUA’、PUA体系中，聚氨酯分子链和丙烯酸树脂分子链形成核壳结构，且在PUA中，聚氨酯分子链和丙烯酸树脂分子链之间形成的化学键，可以有效的提高二者的相容性及共混程度。