Principles of a plasticizer selection

The selection of plasticizers for polyurethane compositions depends on satisfying various tasks such as lowering viscosity, increase in potlife, lowering modulus and hardness of polyurethane, an increase in the low temperature resistartee (lowering the glass transition temperature of soft chains), or dissolution of components in reaction mixture. 

The general reqrtirements for plasticizers for SPU (as well for other polymers) are the low volatility, a high boihng and decomposition points, a low glass transition tempera-titre and melting point (in the case of pronotmced plasticizer ability to crystallize). - Plasticizer should be chemically inert. 

It follows from the mechanism of a specific influence of plasticizers on the SPU properties that for solving a problem of polyrtrethane low temperatirre resistance it is worthwhile to use plasticizers in the presence of which the hard blocks solubility in the 

To lower hardness of polyurethane requires plasticizer capable to dissolve hard blocks of polymer. This causes the decrease in the content of a hard microdispersion phase in SPU and, as a result, the decrease in a mechanic modulus and hardness of material. 

The equilibrium swelling of polyurethane samples in plasticizers is an useful method of initial screening. The plasticizers in which polyurethane swells well are suitable for decrease in hardness. 

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