Study On Synthesis, Structure And Properties Of Polybutadiene/Liquefication Modified MDI-Based Polyurethane Elastomer

Taking a liquid hydroxyl-terminated polybutadiene(HTPB) as prepolymer, liquefication modified MDI as crosslinker, BD or ED as chain extender, we synthesized polybutadiene-based polyurethane elastomer(HTPB-PU). The kinds and the amounts of chain extender, the molecular weight of HTPB as well as fillers and physical and mechanical properties of the HTPB-PU elastomer were studied in details.The modern methods and apparatus such as Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetry (TG) were used to study the structure, morphology and mechanical properties of the elastomers. The results indicate that the properties of the HTPB-PU elastomers are significantly affected by the hard segment contents. Mechanical properties show that the strength and the hardness of the samples increase with the hard segment contents increasing, but the elongation at break decrease with its increasing. At the same time, the relationship between the kinds and the amounts of the fillers and the hydrolytic stability of the elastomer was studied in detail. The studies indicate that the hydrolytic stability of the copolymer increasing with the increasing of the amounts of the filler. With a same amounts of the filler, the mechanical properties of the HTPB-PU elastomer of nanometer CaCO₃ are better than that of the common CaCO₃. The studies also indicate that the mechanical properties and the hydrolytic stability of the elastomer are improved with the increasing of the amounts of the filler.The results of the thermal analysis show that the hydrolytic stability, the thermal decomposition temperature and the glasstemperature (Tg) of the polyurethanes taking BD as extender are better than that of ED as extender. The reaction of HTPB with liquification modified MDI is followed by monitoring the changes of the IR absorption bands of the NCO stretching at 2270cm^{-1}. It was found that the rate of the polyurethane formation obeys an overall second-order kinetics.