Polycarbonates, antiplasticization plasticization

For many years, it has been known that a small quantity of plasticizer acts as an anti plasticizer for polyvinyl chloride (PVC). During a recent search for effective plasticizers for polycarbonate, W. J. Jackson and J. R. Caldwell found several groups of compounds which acted as antiplasticizers. They increased the tensile modulus and strength and reduced the elongation of polycarbonate films. In contrast to plasticizers, these antiplasticizers affected glass transition temperature quite differently. Their mechanism is explained by the fact that they either increase crystallinity or reduce the mobility of the polymer chain through the bulkiness of their molecules. 

The book closes with two chapters on the plasticization and antiplasticization of polycarbonate by A. Conix and L. Jeurissen and G. W. Jackson and J. R. Caldwell, respectively. It would have been possible to include more examples of the interaction between polymers and plasticizers, for instance on the effect in lacquers, in latices, or adhesives. Some are mentioned in the first chapter. 

Whereas Sears and Darby (7) found many types of compounds which would plasticize bisphenol A polycarbonate when the plasticizer concentration was 25 to 30%, the norbornane-tvpe polycarbonates could be plasticized only with larger amounts of plasticizer. When present in concentrations of 20 to 30%, conventional plasticizers acted as diluents—that is, the tensile modulus and tensile strength were depressed, as occurs with plasticizers, but the elongation was not appreciably increased. The antiplasticizers also acted similarly and became diluents after their peak antiplasticizing action was reached. 

The antiplasticization phenomenon is presumably common to all the polymers exhibiting a relatively strong (5 transition, well separated from the a transition. It has been observed for both linear (PVC, polycarbonate, poly-sulphones) and network polymers (amine-crosslinked epoxies). For the case of thermosets, the phenomenon may be a consequence of both internal (change of the network structure) and external (incorporation of miscible additives) modifications of the structure or the composition but it always seems to be a consequence of the plasticization, as shown in Fig. 11.7. 

Polycarbonate appears to an almost unique extent to be subject to an anti-plasticizing effect on the addition of low molecular weight compounds. It is reported that the derivatives of l,l-bis(4-hydroxyphenyl)-2,2-propane operate in this context by tightly filling the free volume between the polymer molecules. Charge-transfer complexes , for example tetracyanoethylene-A-stilbene s, antiplasticizing action has been explained in terms of aandyff relaxations. ... 

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