Antiplasticizers

Antiperspirant sticks Antiplasticization Antiprex Antiprogestin Antiprogestins Antiproliferative agents Antiprotozoal... 

The Tg value is reduced by the addition of moderate amounts of plasticizers (additive which reduces intermolecular forces) and is sometimes even increased by the addition of small amounts of plasticizers (antiplasticization) and optimum amounts of fillers (usually a relatively inert material used as the discontinuous phase of a composite) and reinforcements (materials such as fibrous additives which give increased strength to a polymer). 

Smaller amounts (less than 10%) of plasticizers, actually make PVC more rigid (antiplasticization), but much larger amounts (40%) produce a flexible plastic with a low Tt which can be readily molded and extruded. 

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. 

Since each of these polycarbonates had exceptionally high glass transition temperatures—256° and 290°C., respectively—it was possible to add appreciable amounts of antiplasticizers without depressing the glass transition temperatures to room temperature or lower. In addition, since the bisphenol II polycarbonate already had a relatively high tensile modulus (4.7 X 105 p.s.i.), it was of interest to determine how much this modulus could be increased. 

To determine if the tensile properties of the commercially available polycarbonate from 4, 4 -isopropylidenediphenol were similarly affected, several of the antiplasticizers were also added to this polymer. The bisphenol itself is commonly known as bisphenol A. 

Except for the previously mentioned two films, the moduli decreased when the antiplasticizer concentration was increased to more than 30%. The moduli were still relatively high, however, even when the concentration of the additive was 40 to 50%. 

As the antiplasticizers made the films stiffer, their elongations decreased. The tensile strengths, in most cases, increased. As is shown in Table II, when the amount of additive was increased to more than 30% and the modulus decreased, the tensile strength also decreased. Tensile strengths and moduli also decreased when the additive was not an antiplasticizer. 

Figure 2 shows the effect of two Aroclors on the glass transition temperatures. A very rapid decrease in transition temperatures of the polymers from bisphenols I and II took place when as much as 5 or 10% additive was in the films. When the antiplasticizer concentration was 5 to 30% in the bisphenol I polymer and 10 to 40% in the bisphenol II polymer, there was a linear relationship between the decrease in glass transition temperature and the antiplasticizer concentration. 

The heat-distortion temperatures in the tables are the temperatures at which the films distorted 2% while under a load of 50 p.s.i. Except for examples in which the antiplasticizer concentration was 40 to 50%, the heat-distortion temperatures were usually within 10°C. of the glass transition temperatures, which are the temperatures at which the films distorted 0.25% while under a load of 5 p.s.i. Distor-... 

It is surprising that the tensile moduli of the polycarbonate films were increased so much by the antiplasticizers, and it is even more surprising that antiplasticizer concentrations of 30% (and even 40% in two cases) could be tolerated before the... 

The DTA endotherms of the antiplasticized polymers indicate the presence of forces which are broken by the input of thermal energy. Instead of a degree of order or incipient crystallization, it is possible that these forces consist of secondary bonds... 

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 antiplasticizing action has been described here for only three classes of commercially available antiplasticizers, but it has been observed, usually in a lesser degree, with other classes of compounds and low molecular weight polymers. These are, however, not commercially available. Bisphenol polyesters of isophthalic acid, terephthalic acid, and 1,4-cyclohexanedicarboxylic acid also have been antiplasticized the polymer chains, as would be expected, are all relatively rigid. 

We would like to acknowledge the technical assistance of J. L. Beach and H. G. Moore and very helpful discussions concerning the antiplasticizing action with R. M. Schulken, Jr. 

In some polymers, addition of very small amounts of diluent seems to fill up the holes in the liquid structure and the dynamics actually slow down. This antiplasticizer effect has not yet been examined with PCS, but this technique should prove very useful. The whole area of the effect of dilution on the PCS of bulk polymers is very promising and virtually unexplored. 

The water solubility of R-(EO)n types of nonionic emulsifiers is derived from the weak interaction between the ether oxygen of EO unit and water. It was suggested that each EO unit in the PEO chain, requires three molecules of water to form a hydrated complex [35]. This hydrogen bond complex is destroyed if the solution is taken above the melting point of the PEO. Water usually acts as plasticizer when present in hydrophilic PEO polymers and Tg values decrease with increasing water contents [36]. This phenomenon in the PEO-water system is observed up to 1 mol water/ether group. Beyond this a rise in Tg is observed and water acts as an antiplasticizer. 

Carbon-13 rotating-frame relaxation rate measurements are used to elucidate the mechanism of gas transport in glassy polymers. The nmr relaxation measurements show that antiplasticization-plasticization of a glassy polymer by a low molecular weight additive effects the cooperative main-chain motions of the polymer. The correlation of the diffusion coefficients of gases with the main-chain motions in the polymer-additive blends shows that the diffusion of gases in polymers is controlled by the cooperative motions, thus providing experimental verification of the molecular theory of diffusion. Carbon-13 nmr relaxation... 

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