Bayer has developed two new low-NCO prepolymers, Baytec® MP-020 and Baytec MP-030, that are ideal for making soft elastomers.

Bayer Corp.’s Polyurethanes Division, Pittsburgh, has developed two new low-NCO prepolymers, Baytec® MP-020 and Baytec MP-030, that are ideal for making soft elastomers. Both materials are diphenylmethane diisocyanate-terminated polyether prepolymers based on polypropylene ether glycol.

“These new materials are excellent for a variety of applications that require soft elastomers,” said George J. Schexnayder, senior marketing specialist for Bayer’s Polyurethanes Division. “Applications range from bicycle seats and computer-keyboard wrist pads, to rubber-crumb flooring and flexible caulks and sealants.”

Schexnayder noted that low-NCO prepolymers are relatively new for Bayer Corp. The NCO content of Baytec MP-020 is in the 2.4- to 2.8-percent range, and that of Baytec MP-030 is in the 3.5- to 4.1-percent range. Typical isocyanate-terminated prepolymers have an NCO content of about 6 percent.

Both Baytec MP-020 and MP-030 prepolymers are suitable for making one-component, moisture-cured binders, sealants and ultrasoft elastomers. Baytec MP-020 has a high viscosity (55,000 mPa at 25ºC), which can be reduced by blending with diluents. It reacts faster than Baytec MP-030, and is particularly suitable for developing caulking and sealant systems. Baytec MP-030 has a lower viscosity (8,000 mPa at 25ºC) despite its low-isocyanate content, and because of its somewhat slower reactivity is better suited for larger-volume mixing applications, such as binding cork or rubber crumb. Both materials are liquids at normal room temperatures.