THE ROLE OF H YDROX YL TERMINA TED POLYBUTADIENE IN SPECIAL POLYURETHANE FORMULATIONS A THESIS

Abstract

ABSTRACT Hydroxyl-terminated polybutadiene (HTPB) resins occupy a unique position among the commercially available polyols. This class of materials may be used to prepare polyurethane elastomers that are characterized by low temperature flexibility, hydrophobicity and hydrolytic stability. Due to the hydrocarbon nature of the polymer backbone, these elastomers also possess extremely low dielectric constant, dissipation factor, and low MVTR (moisture vapor transmission rate) properties. Depending on the hydroxyl functionality and backbone microstmcture, namely, the l,2-vinyl, 1,4-cis, or 1,4-trans distribution of each repeating unit, the HTPB- derived polyurethane elastomers can have a wide range of physical properties including glass transition temperature and viscosity. This thesis is concemed with the role of (HTPB) as a soft segment in the preparation of special polyurethane which can be utilized in composite binding system, based on the following materials: I Hydroxyl terminated poly butadiene as a pre polymer. 0 2,4 toluene diisocyanate as a curing agent. 0 dioctyl sebacate as a plasticizer. 0 Tris methyl azidrinyl phosphinoxide(MAPO) as a cross linker. the dynamic mechanical behavior was studied followed by morphological studies using, (Electron Scan Micrograph), by tracing the different behavior of results regarding the relation between sofi segment and hard segment, and the means of controlling the disorder played by the long chain and entangled soft segment. MAPO was used as a cross linker in this manner. Different parameters has been gathered for tailoring a binding system, based on (HTPB) pre polymer, which can fit for use in solid composite propellants. ll