Recent Developments in Polyurethane Cast Elastomers for MOCA Replacement with ETHACURE® 300

摘要

ETHACURE® 300 curing agent (E300) is a low viscosity, liquid aromatic diamine. It can be used as a chain extender to make strong, flexible materials called elastomers as well as in coatings, adhesives, rigid foam insulation, flexible foam cushions and countless other items. Albemarle continues to use experimental and computational approaches, such as DOE, to improve performance of E300. Recently, a series of experiments have been conducted in the curative lab to enhance the properties of cast elastomers cured with E300. One of the concerns of using PU cast elastomers in certain applications is the susceptibility of the elastomers to solvents. When exposed to various solvents for extended periods of time, polyurethanes experience changes in weight and volume due to the solvent softening the polymer and solvent retention. This change leads to decreased performance and possible part failure. The solvent resistance of PU elastomers cured with E300 and MOCA was investigated in various solvents. The results indicated the elastomers cured with E300 perform equivalently to MOCA cured elastomers, but demonstrated a significant advantage in ASTM Oil #1, 10% Nitric Acid and 10% NaOH. Reactivity in PU cast elastomers is very important since only a limited amount of time is usually available to meter, mix, and pour materials into open molds. The liquid nature of E300 curative gives the processor a degree of control over processing conditions. The reactivity of E300 with prepolymer can be adjusted by raising or lowering prepolymer temperature, which is not available in the use of a solid curative (i.e. MOCA). The study reveals a 15°C drop in prepolymer nearly doubles the pot life of the mixture. The higher reactivity was observed in the use of prepolymer with higher NCO%. The pot life decreases with an increase of NCO% in the prepolymer. In our study, we discovered the processing temperature had a significant effect on the mechanical and dynamic properties of the elastomers. The tensile and tear strength of the elastomers were increased by 22% and 39%, respectively, with the increase of post cure temperature of 30 degree. The dynamic property was improved accordingly as the processing temperature increased. The E300 cured elastomer demonstrates superior performance over MOCA cured elastomer after exposure to high temperature over an extended period (i.e. 50 days at 100°C). To further improve and optimize the dynamic properties of elastomer cured with E300, Design of Experiments (DoE) was used in this study. Variables, such as index, the ratio of prepolymers, processing temperature, etc. were considered to optimize the dynamic property. The optimum design exhibits the superior dynamic property over MOCA from -30°C and 130°C. The value of the compression set of the optimum design is 17, whereas the elastomer cured with MOCA is 29. The obtained results and information discussed in this poster will provide a foundation for customers to design PU elastomers with desired properties for various applications.