How much plasticizer is necessary for a polymer composition

Selection of plasticizer should be based on main characteristics of plasticizer and polymer. Plasticizer characteristics determine its amoimt which can be added into composition and the thermodynamic stability of mixture. 

In some cases, plasticization is used to convert a polymer to an elastic material. PVC is often treated in this manner. PVC in its non-plasticized state has a Tg above the room temperature and consequently has a limited ability to deform. The addition of substantial amounts of plasticizer results in a highly elastic material in which a large strains will not cause irreversible deformation because of partial crystallization of polymer. To produce such effect the plasticizer mrrst have good compatibility with the polymer. But the high degree of compatibility should not interfere with crystallization at the normal operating temperatures otherwise plastic system will be formed rather than the preferred elastic. 

For crosslinked elastomers (rubbers), plasticization ttsually causes a decrease in the glass transition temperature and an increase in the temperatirre range in which the elastomer will perform. A in there is a need for good compatibility of the polymer and plasticizer and the glass transition temperature of the plasticizer should be as low as possible. 

Often plasticization is rrsed to improve processability by reducing viscosity at processing temperatures. The viscosity decrease is related less to compatibility between the plasticizer and polymer. Frequently, viscosity reduction results from plasticizer playing the role of an interior lirbricant that does not dissolve the polymer. 

Material scientists can predict an approximate amormt of plasticizer reqirired for composition irsing experience, because marty plasticizers reduce viscosity of a polymer nearly to the same extent (this statement has, certainly, a lot of exceptions). In some applications 75% polymer in a composition with 25% plasticizer gives ttseftrl properties over a temperatirre range of material rrse (e.g., lowering low temperature properties of butadiene-nitrile rabbets by 10-15 C with preservation of remaining technical properties). In other 

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