Evaluating a Secondary Aliphatic Diamine Curative in Colorless, Light-Stable, IPDI-Based Polyurea Coatings Using a New, Low-Pressure, Static-Mixing Technique

A static-mixing technique has been developed that mimics high-pressure, impingement mixing for spraying fast-reacting, polyurea coatings. The static-mixing technique uses many of the same parameters found in high-pressure, impingement-mixing spray equipment, and it functions as an excellent formulation screening tool. The finished products are almost identical to those made using high-pressure RIM techniques, but without the microbubbles. This new tool has been used to evaluate the performance of UOP’s new light-stable secondary aliphatic diamine. Clearlink ™ 1000 diamine is a clear, colorless, low-viscosity liquid with an equivalent weight of 161. The reaction kinetics are dramatically slower than those of primary aliphatic diamines but faster than aromatic diamines. Clearlink 1000 is designed to work with impingement-mixed and sprayed, light-stable polyurea coatings to increase the working time, enable the deposition of a more uniform coating, improve wettability, facilitate multiple passes, improve adhesion, and improve the overall strength properties of the coating. The use of Clearlink 1000 in formulations based on isophorone diisocyanate (IPDI) and polyetheramines is particularly advantageous. In this paper, we have used low-pressure , static mixing at room temperature to produce clear, colorless coatings in the hardness range of 56 Shore A to 60 Shore D. The tensile strength values for the harder coatings were as high as 4,000 psi with elongation values above 500%. The tear resistance values were typically above 400 pli and the tear propagation values were usually above 300 pli. The 56 Shore A coating had a tensile strength of over 900 psi and an elongation of over 875%. A 48 Shore D coating was produced with a tensile strength of 4,170 psi and an elongation of 600%.