Improved Processability and Performance in MDI Elastomers Based on Ultra-Low Monol Polyols

摘要

In the last decade,opportunities for improving the performance of polyurethane systems based on polypropylene glycols(PPGs)have increased greatly due to the availability of ultra-low monol(ULM)PPGs.These polyols have found acceptance in a wide variety of CASE applications because of their performance-enhancing capabilities,consistent quality and/or lower cost relative to poly(tetramethylene ether glycol)(PTMEG).Although the use of ULM polyols provides a significant improvement in elastomer properties over those obtained with conventional PPGs,their performance in 4,4'-diphenylmethane diisocyanate prepolymer systems cured with 1,4-butanediol(MDI/BDO)has remained below that obtained with PTMEG.Despite their low monol contents,the properties and processability of MDI/BDO/ULM elastomers have been limited by low polymer molecular weight resulting from excessive phase separation.Formulating approaches for increasing polymer molecular weight by controlling the rate of phase separation have been developed.These offer significant improvements in processability and elastomer properties such as hardness,modulus,tensile strength,abrasion resistance,and load bearing.The approaches discussed in this paper allow the benefits of ultra-low monol levels to be fully realied in MDI/BDO systems.