Curing Mechanism of Hydroxyl-Terminated Polybutadiene (HTPB) Formulated with Isophorone Diisocyanate (IPDI) as Revealed Using Raman Spectroscopy

Abstract

Hydroxyl-terminated polybutadiene (HTPB) is used in a variety of formulations, particularly for military and aerospace applications as a binder for energetic materials. This work investigates details of its curing process when formulated with isophorone diisocyanate (IPDI). Raman spectroscopy was used as a fast, sensitive, non-destructive technique to monitor the curing process of HTPB-IPDI. A significant feature at 777 cm^–1 was shown to grow over the course of the curing process. Ab initio calculations of the normal modes of the HTPB-IPDI dimer indicate that this feature is most likely connected to the urethane bond, which suggests that the feature at 777 cm^–1 is associated with formation of the urethane linkage as the formulation cures. Raman spectroscopy thus has potential to be used for quality assurance and other material state awareness measurements for HTPB-IPDI materials.

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Keywords

Polymer processing curing of polymer formulation curing of polyurethane materials Raman spectroscopy materials state awareness

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