Benefits & Applications 1,4-Butanediol (1,4-BDO) versatile chemical intermediate because of its terminal, primary hydroxyl groups and its hydrophobic and chemical resistant nature. Polymers produced upon reaction with diacids or diisocyanates are the basis for many commercial polyurethane and polyester applications. 1,4-BDO is used to manufacture polybutylene terephthalate (PBT), thermoplastic copolyester elastomers or as a component of polyesters or as a chain extender in polyurethanes. On comparison to other diols, 1,4-BDO combines the best attributes of hydroxyl reactivity, linearity and overall system compatibility to build in the proper crystallinity required in the polyurethane hard segment. Also, the 1,4-BDO/MDI systems provide a lower exposure hazard than MOCA/TDI systems. In thermoplastic urethane elastomers, 1,4-BDO yields crystalline urethane domains which readily melt and flow at elevated temperatures but phase separate at ambient temperatures in order to yield tough elastometric networks. Cast urethane elastomers continue to be a major end use of 1,4-BDO because of overall consistency and reliability. Urethane RIM elastomers using 1,4-BDO allow design freedom and parts consolidation with large, complex shapes.