Particle Size Of Polyurethane Dispersions Research Articles

Effects of castor oil, glycol semi‐ester, and polymer concentration on the properties of waterborne polyurethane dispersions

AbstractA series of waterborne polyurethane dispersions (PUDs) were synthesized using castor oil, polypropylene glycol, toluene diisocyanate, and (2E)‐4‐(2,3‐dihydroxypropoxy)‐4‐oxobut‐2‐enoic acid [glycol semi‐ester (GSE)]. These PUDs can be crosslinked spontaneously upon drying, without extra additives or processing steps. Moreover, the rheological properties, particle size, and morphology of PUDs were examined with stress‐controlled rheometer, light scattering ultrafine particle analyzer, and transmission electron microscopy. Results reveal that the particle size of PUDs mainly depends on the concentrations of castor oil, GSE, and polymer. With the increase of GSE concentration and the decrease of castor oil and polymer concentration, the particle size decreases. This can be ascribed to the decrease of the particle size of the polymer dispersion, because of the decrease of the relative size of water layer to total particle size. Furthermore, increased amount of castor oil, GSE, and polymer concentrations results in an increased viscosity of PUDs because of the increase of effective volume for the dispersed phase. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers

Effects of carboxyl groups dissociation and dielectric constant on particle size of polyurethane dispersions

Aqueous polyurethane (PU) dispersions were prepared by pre-polymer mixing and the neutralization emulsification method. PU dispersions were electrostatically stabilized with carboxyl groups incorporated into their particles, which were neutralized by triethylamine (TEA). The reaction parameters were molecular weight of polyol, amount of chain extender, TEA/dimethylolpropionic acid mole ratio, and the dielectric constant of the dispersion medium. The average particle sizes ranged between 27 and 415 nm. Owing to an enlargement of the stabilization site, the particle size decreased as the concentration of carboxyl groups and the degree of neutralization increased.

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

AbstractA 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.