Polymer plasticizer effect

Doping a neat glass forming system with smaller molecules leads to a reduction of the glass transition temperature Tg.176 In polymer research, this behavior is well known as polymer/plasticizer effect. However, it applies to any mixture provided that the Tg value of the additive is significantly lower than that of the main component. 

This behaviour was explained as owing to a process of supramolecular structure loosening as a result of a polymer plasticization effect determined by CO2, which allowed quicker removal of CO2 [17]. The obvious consequence was that the kinetics equations established for every particular case (PUs sheet thickness or CO2 concentration) depended on the initial CO2 concentration. 

The plasticization of PVC accounts for the vast majority of plasticizer sales. However, significant amounts of plasticizers are used in non-PVC polymers and this may become increasingly important in the future. Although PVC stands alone in its abiUty to accept and retain large quantities of commercial plasticizer, effective plasticization of other resins using slightly modified plasticizers may be possible if certain conditions specific to the polymer of interest are met. 

Plasticization and Other Time Effects Most data from the literature, including those presented above are taken from experiments where one gas at a time is tested, with Ot calculated as a ratio of the two permeabihties. If either gas permeates because of a high-sorption coefficient rather than a high diffusivity, there may be an increase in the permeabihty of all gases in contact with the membrane. Thus, the Ot actually found in a real separation may be much lower than that calculated by the simple ratio of permeabilities. The data in the hterature do not rehably include the plasticization effect. If present, it results in the sometimes slow relaxation of polymer structure giving a rise in permeabihty and a dramatic dechne in selectivity. 

More than one plasticizer could be used. One is the main plasticizer and the other (or others) is the secondary plasticizer. The compatibility between the plasticizers and the polymers in the blending system, especially the major component, is necessary to obtain the best plasticizing effect. Combining the main plasticizer and secondary plasticizer(s) usually gives better results. 

As Carfagna et al. [61] suggested, the addition of a mesophasic polymer to an amorphous matrix can lead to different results depending on the properties of the liquid crystalline polymer and its amount. If a small amount of the filler compatible with the matrix is added, only plasticization effect can be expected and the dimensional stability of the blend would be reduced. Addition of PET-PHB60 to polycarbonate reduced the dimensionality of the composite, i.e., it increased the shrinkage [42]. This behavior was ascribed to the very low... 

The increase in the length of the side chain results normally in an internal plasticization effect caused by a lower polarity of the main chain and an increase in the configurational entropy. Both effects result in a lower activation energy of segmental motion and consequently a lower glass transition temperature. The modification of PPO with myristoyl chloride offers the best example. No side chain crystallization was detected by DSC for these polymers. 

Lai, M.C., Hageman, M.J., Schowen, R.L., Borchardt, R.T., Laiard, B.B., and Topp, E.M. 1999b. Chemical stability of peptides in polymers. 2. Discriminating between solvent and plasticizing effects of water on peptide demidation in poly(vinyl pyrrolidone). J. Pharm. Sci. 88, 1081-1089. 

On the other hand, Bhattacharya et al. have reported the plasticization effect of organically modified layered silicates on dynamic mechanical properties [13]. In this work, nanocomposites of SBR have been prepared using various nanofillers like modified and unmodified montmorillonite, SP, hectorite etc. It has been observed that the Tg shifts to lower temperature in all the nanocomposites, except for systems from hectorite and NA. This is due to the fact that clay layers form capillaries parallel to each other as they become oriented in a particular direction. Due to wall slippage of the unattached polymer through these capillaries, the Tg is lowered, which could be even more in the absence of organo-modifiers [13]. A similar type of plasticization effect is also noted in the case of the low... 

The same effect is borne out by our experiments. The Tf s of solvent-cast nlms were higher than those clot era lined on pressed films made from the same polymer plasticizer mixtures. 

Thus different phase behaviors of polyrotaxanes induced different thermal transitions. One-phase or two-phase materials can be obtained simply by proper choice of the components. The easy introduction of highly flexible cyclic components such as crown ethers with low T% surely expands the applications of otherwise brittle polymers into the low temperature range and also improves elasticity. The plasticizing effect of the crown ether is different from that of a normal plasticizer, because the cyclic is permanently connected to the backbone and no migration can occur. 

The so called plasticization effect, i.e., the depression of the glass transition temperature is also an important feature the sorbed gas acts as a kind of lubricant , making it easier for chain molecules to slip over one another, and thus causing polymer softening. 

The model of Condo permits the determination of the limiting pressure at which the glass state exists, on the basis of a reduced number of parameters (only the glass transition temperature of the pure polymer is needed to calibrate the energy parameter) for this reason, it seems particularly useful for the prediction of the plasticizing effects. 

Some radiation effects in long chain polymers. Plastics Institute Trans. 23, 133-138 (1955). 

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