Advances in NDI Elastomer Chemistry

Since its first commercial use in the early fifties naph thalene-1,5-diisocyanate (NDI) has been used almost exclusively in combina tion with polyadipate diols. The corresponding prepolymers crosslinked with 1,4-butanediol give solid NDI elastomers; crosslinking with water results in microcellular elastomers. NDI/ester elastomers are known for high performance and long service life in particularly demanding dynamic applications. Although polyadipate soft seg ments are the preferred building blocks to ensure high structural strength of polyurethane elastomers, their sensitivity towards hydrolysis and microbical attack demands the addition of special additives for some applications. The combination of NDI with alternative polyols, such as polytetramethy leneglycol (PTMEG), hexylene adipate, and ether carbonates alleviates these problems and expands the usage area of NDI elastomers. Of particular interest is a dihexylene carbonate that combines the property advantages of an ester backbone with the hydrolysis resistance of a polyether polyol. In this paper we discuss the results of static and dynamic tests designed to compare the proper ties of NDI elastomers having different soft segment contents. An interesting approach to the utilization of naphthalene-1,5-diisocyanate for low hardness solid elastomers is crosslinking with water. Although these