The Study On Thermoplastic Polyurethane Elastomers

Thermal polyurethane elastomers are widely used in various industries such as mining, oil field, machinery, transportation, and architecture because of their excellent physical chemical and mechanical properties, the melt fluidity is also important to the processability of thermal polyurethane elastomer, the thermal polyurethane elastomers could be used more widely with both high mechanical properties and melt fluidity. However, the molecular weight, melt fluidity and mechanical strength are mostly contradictory, and it is difficult to be controlled in synthesis.For the purpose of improving the mechanical property while maintaining the thermoplastic of TPU, hydroxy-terminated polystyrene was used to compounded with polyurethane prepolymer. A series of polystyrene-polyurethane-polystyrene (SPUS) based on hydroxy-terminated polystyrene and polyurethane prepolymer were prepared by solution polymerization, which advances a new way to modify polyurethane by polystyrene. The structure and morphology of SPUS were characterized by FTIR, GPC, DMA, XRD, TEM. The results of TEM revealed that PU possesses the ability to coordinate with PS, resulting in the phase separation in the SPUS. Effects of the mass fraction and the molecular weight of hydroxy-terminated polystyrene on the mechanical properties of SPUS were investigated. The results showed that SPUS possessed relatively high tensile strength and elongation at break than TPU under the approximate molecular weight circumstances while maintaining approximate melt fluidity. the increase in mass fraction of PS could increase the tensile strength of SPUS, when the molecular weight and mass fraction of hydroxy-terminated polystyrene is 10000 and 25%, SPUS possessed the best mechanical properties.A series of thermal polyurethane based on polyether polyols as soft segments, Diphenylmethylene diisocyanate (MDI) and micromolecular diatomic alcohol as hard segments were synthesized by prepolymer method. The effect of isocyanate index, chain extender, the mole ratio of mixed chain extender to the properties of thermal polyurethane were discussed. The results showed that thermal polyurethane possessed comparatively better mechanical properties and higher fluidity when the NCO/OH is 0.99; Polyurethane hot melt adhesive based on bisphenol A possessed higher melt index, and thermal polyurethane based on diethylene glycol and bisphenol A when the n(bisphenol A)/n(diethylene glycol) is 1/3 maintain excellent mechanical properties and melt fluidity after treated by high temperature.