Polymer-plasticizer interactions

Since the equations developed by these earher authors are quite simple, they can only be reasonably applied in a narrow range of temperatures around Tg and to systems in which polymer-plasticizer interactions are not too strong. Additioiially, they contain parameters, such as the glass transition temperature of the plasticizer, that are sometimes difficult to obtain. Moreover they have been criticized since they do not take into account the interaction between the plasticizer and the polymer or the dependence of efficiency on the molecular structure. 

The phase diagrams represent polymer-plasticizer interactions described by the general equations of state (pressure-volume-temperature). But the generation of such equations is very difficult and can be done only for selected systems. ... 

The theory of solutions assumes that molecules are spherical. For long-chain polymer molecules, consisting of segments, the number of modes of arrangement in a solution lattice differs from those of spherical molecules. This results in deviations from the ideal entropy of mixing. The polymer-plasticizer interaction differs qualitatively because of the presence of segments coimected into chains. 

The strength of the polymer-plasticizer interaction depends both on the chemical stracture and on the concentration of the plasticizer. A compatible plasticizer, especially at a low concentrations, is difficult to remove. For example, at a 10% concerrtration in PVC, a complete extraction plasticizer by gasoline is not possible even over 96 hrs. ... 

As mentioned above, the macromolecules develop into more extended conformations in a good solvent or plasticizer. This increases the viscosity of dilute solutions of polymer. Viscosity changes are used for comparative evaluation of polymer-plasticizer interaction. The plasticizer may also decrease the interaction between polymeric chains and this reduces the viscosity of concentrated polymeric solutions. Incompatible plasticizers, on the other hand, may considerably reduce the viscosity of polymer compositions even in small quantities (less than 1%) by acting as internal lubricants. 

In addition to plasticizer and the resin, other additives are included in composition, such as for example antioxidants" or UV stabilizers." " Figure 11.42 shows that with small additions of a plasticizer an antioxidant dissolves better than predicted by a sum of its solubilities in polymer and plasticizer. Larger additions of the plasticizer cause a strong polymer plasticizer interaction which decreases the antioxidant dissolution." Figure... 

Molecular weight of a polymer and a certain concentration of the plasticizer determine the uniformity blend. If the molecular weight of PVC used in CPE-PVC-DOP blend is doubled, the concentration of DOP needed to obtain a homogeneous mixture is increased from 55 wt% to 70 wt% of DOP. A statistical thermodynamic approach was developed for mixing of polymers, small molecules (plasticizers), and holes which are different in sizes. Plasticizer efficiency is determined by polymer-plasticizer interaction and plasticizer segment size. 

The analysis of dependence of melting temperature on plasticizer content in the range in which PLA and acetyl tri-n-hutyl citrate (ATBC) are miscible gives indications of polymer-plasticizer interactions (Baiardo et al, 2003). The Flory (1953) equation fits well for miscible polymer-diluent mixtures ... 

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