Practical approaches in using theory of compatibility for plasticizers selection

4 PRACTICAL APPROACHES IN USING THEORY OF COMPATIBILITY FOR PLASTICIZERS SELECTION 

Knowledge of the laws of thermodynamic makes the process of plasticizer selection easier. As was mentioned in Subchapter 6.1.3, compatibihty of polymers and plasticizers is related to the enPopy and enthalpy effects. Often they work in combination 

The mle like dissolves like is only partially useful because it is not valid for polar polymers. Polar polymers are compatible only with some polar plasticizers. Interaction of polar polymers and plasticizers depends on the presence and arrangement of groups capable of donor-acceptor interactions. Polar plasticizers with a proton-acceptor character (esters, ethers, and nitriles) are most useful for polymers having average polarity (e.g., PVC, PC, and butadiene-aciylonitrile copolymers). For other polar polymers, especially those soluble in water, plasticizers containing OH-groups are more effective. 

The arrangement of polar groups may be more significant if internal hydrogen bonding can occur. If there is a strong interaction of this type, compatibility decreases, because plasticizer-plasticizer interaction is preferred over plasticizer-polymer interaction (tri-cosane is five times more soluble in butanol than in ethanol). 

These effects are part of the solubility parameters concept. This concept allows to predict compatibility qualitatively (see Section 6.2). Within the framework of the general principles of the thermodynamics of solutions, the numerical evaluation of compatibility implies the evaluation of the value of the free energy (the Gibbs energy) of mixing over the whole range of solution concentration. However, sueh evaluations are difBcult and often excessive for most practical purposes. Therefore, for the estimation of compatibility, it is more convenient to know the value of aity numerical criterion mentioned in the previous subchapters. 

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Practical approaches in using theory of compatibility for plasticizers selection... 

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