Polyurethane elastomers ultimate tensile

Elastic Modulus, Network Structure, and Ultimate Tensile Properties of Single-Phase Polyurethane Elastomers... 

The equilibrium shear modulus of two similar polyurethane elastomers is shown to depend on both the concentration of elastically active chains, vc, and topological interactions between such chains (trapped entanglements). The elastomers were carefully prepared in different ways from the same amounts of toluene-2,4-diisocyanate, a polypropylene oxide) (PPO) triol, a dihydroxy-terminated PPO, and a monohydroxy PPO in small amount. Provided the network junctions do not fluctuate significantly, the modulus of both elastomers can be expressed as c( 1 + ve/vc)RT, the average value of vth>c being 0.61. The quantity vc equals TeG ax/RT, where TeG ax is the contribution of the topological interactions to the modulus. Both vc and Te were calculated from the sol fraction and the initial formulation. Discussed briefly is the dependence of the ultimate tensile properties on extension rate. 

Priorconcomitant work on this problem at the Jet Propnlsion Laboratoi indicated that an elastomer based on the Thiokol Chemical Company s Solithane family of polyurethanes most nearly fulfilled these goals. Hence, one particular formulation of Solithane 113 was adopted as an interim standard. This is called GALCIT I. Its major defects are that the chemical structure is not sufficiently well defined, its properties change slowly with time, and its ultimate elongation in a uniaxial tensile test at 25 C is only about 7056, This means that it is an inadequate vehicle for large deformation studies,... 

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