Understanding the role of isocyanate dilution toward spraying of polyurea

Abstract

ABSTRACTAn experimental study into the consequences of diluting isocyanate toward processing of polyurea has been reported. The effect of introducing increasing amount of propylene carbonate into a representative isocyanate precursor has been established. Viscosity‐blending index based equations were found to be more reliable toward prediction of isocyanate precursor‐propylene carbonate blend viscosity. Spraying of undiluted isocyanate precursor with amine formulations led to formation of “noodle‐like” fibrous product, irrespective of the type of chain extender being used. Diluting isocyanate with propylene carbonate (10% v/v), lowered the viscosity of the precursor from 85 to 48 mPa s (at 70 °C), and the resulting formulations could be effectively sprayed to form polyurea films with excellent mechanical properties. Dilution with propylene carbonate also increased the “tack free” time appreciably from ∼1 to ∼4 s, which directly reflects on the improved processability. Rheological studies were performed to quantify the activation energy associated with the isocyanate‐amine reaction for polyurea preparation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45869.