Plasticization of Polymers

A plasticizer is a material that enhances the processibiIity or flexibility of the polymer with which it is mixed. The plasticizer may be a liquid or solid or another polymer. For example, rigid polyfvinyl chloride) is a hard solid material used to make credit cards, pipe, house siding, and other articles. Mixing with about 50-100 parts by weight of phthalate ester plasticizers converts the polymer into leathery products useful for the manufacture of upholstery, electrical insulation, and other items. Plasticizers in surface coatings enhance the flow and leveling properties of the material during application and reduce the brittleness of the dried film. 

Some degree of solvency of the plasticizer for the host polymer is essential for plasticization. Not surprisingly, a match of solubility parameters of the plasticizer and polymer is often a necessary but not a sufficient condition for compatibility. In the case of PVC, the dielectric constants of the plasticizer should also be near that of the polymer. 

It is often useful to employ so-called secondary plasticizers, which have limited compatibility with the host polymer. Thus, aliphatic diesters are poorly compatible with PVC, but they can be combined with the highly compatible phthalate ester plasticizers to improve low temperature properties of the blend. 

Continued addition of a plasticizer to a polymer results in a progressive reduction in the glass transition temperature of the mixture. This suggests that the plasticizer acts to facilitate relative movement of macromolecules. This can happen if the plasticizer molecules are inserted between polymer segments to space these segments further apart and thus reduce the intensity of polymer-polymer interactions. Such a mode of action is probably characteristic of low temperature 

Rubbers are plasticized with petroleum oils, before vulcanization, to improve processability and adhesion of rubber layers to each other and to reduce the cost and increase the softness of the final product. Large quantities of these oil-extended rubbers are used in tire compounds and related products. The oil content is frequently about 50 wt% of the styrene-butadiene rubber. The chemical composition of the extender oil is important. Saturated hydrocarbons have limited compatibility with most rubbers and may sweat-out. Aromatic oils are more compatible and unsaturated straight chain and cyclic compounds are intermediate in solvent power. 

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Investigation of a wide range of block copolymers, consisting of various flexible (polydimethylsiloxane, polybutadiene) and rigid (polycarbonate, polysulphone, polyarylate) phases [44], shows that irrespective of the chemical nature of copolymer, content and molecular weight of blocks as well as pressure and composition of the hydrocarbon mixture, sorption, and mass transfer of alkanes take place primarily in the rubbery phase. The phenomenon of plasticization of polymers by hydrocarbons was demonstrated by baromechanical methods [7,45 8]. Figure 9.13 shows baromechanical curves for the block copolymer... 

Plasticization—an evaporating solvent which is also a plasticizer of polymer solute product will lead to greater levels of collapse and shrinkage. 

Water-induced plasticization of polymers by disruption of intermolecular hydrogen bonding between polymer chains that are generally considered to be hydrophobic is rather common. Moy and Karasz [30] show that the lowering of Tg for an epoxy-diamine resin is proportional to the amount of water in the system. 

Nature and Amount of the Dispersed Rubber Phase. The effect of the nature of the dispersed rubber phase became apparent during our work on selective plasticization of systems containing two resins A and B, a corresponding AB Cop, and a selective plasticizer of polymer A or B (13, 14) where A was polystyrene (PS) and B was poly (methyl methacrylate) (PMM) or poly (vinyl chloride) (PVC). Selective plasticization is a new method of obtaining resin elastomeric systems which have the advantage that the physical properties (e.g., mechanical properties and refractive index) of the rubbery phase can be varied by the nature and amount of the plasticizer. For such systems, impact resistance is maximum when the energy absorption capacity of the rubbery phase is maximum (e.g., for a given amount of plasticizer with respect to the dispersed phase). 

In terms of security, they are often irreplaceable. This is the case of the airbag in automobiles. Without polymers, how can we achieve this protective ball With a pig s bladder But then, how to integrate onto this skin the very sophisticated technology which allows the liberating explosion of the ball without injuring the driver There is no solution outside the plasticity of polymers. So, today, 50% of plastics applications in the automotive sector are no longer substitutable. 

Figure 15.5 Effect of level of merci tan modifier upon (a) the gel content and (b) the plasticity of polymer obtained after 12 h reaction at SO°C, for styrene-butadiene rubber produced by emulsion pcdymraizafion (Bebb et al. [17]). Reaction foimulatitHi (parts mass) sonene 25, buta ne 75, water 180, soq> 5, potassium posulphaie OJ, dodecyl mercaptan variable (see abscissae of plots)...

ZHA Zhang, Z. and Handa, Y.P., An in situ study of plasticization of polymers by high-pressure gases, J. Polym. Sci. PartB Polym. Phys., 36, 977, 1998. 

ALE Alessi, P., Cortesi, A., Kikic, I., and Vecchione, F., Plasticization of polymers with supercritical carbon dioxide experimental determination of glass-transition temperatures, J. 

The first two theories which try to explain the plasticization of polymers were the gel theory and the lubricity theory. Both were developed simultaneorrsly and sometimes the authors to whom the theories are attributed were not aware of the differences between both... 

The change of PU properties as a result of the plasticization process does not always correspond to the well-known views on the plasticization pattern, which were developed based on investigations of plasticized polymers having a uniform chemical stmcture of soft and hard phases (for example, PVC and esters of cellulose). In fact, the traditional views on plasticization of polymers are not suitable for explanation of maity effects observed by blending different plasticizers in polyurethane material. This behavior can be demonstrated on an example of segmented polyether-urethane-ureas. Their initial stmcture and properties (without plasticizers) are widely investigated. 

The traditional views on plasticization of polymers are based on results of studying the single phase polymer systems and microheterogeneous polymers which have the same chemical stmctures of hard and soft phases. 

Thus, we can state that the use of hyperbranched polyimides can enhance the resistance to plasticization of polymer membranes. 

Acrylic plastics n. Thermoplastic or thermosetting plastics of polymers including copolymers of acrylic acid, methacrylic acid, esters of these acids or acrylonitrile. 

To one of the major factors determining resistance of polymers to shock loadings, plasticity of polymeric materials and improvement of this characteristic of polymers concerns will promote increase of shock durability of samples. Told practically proves to be true the data received as a result of research of influence PhOC on impact strength the block-copolyester on a basis diphenylolpropane, and also industrial polyarilate DV- salts are more effective modifiers by way of improvement of shock dmability and as it was shown above, plasticity of polymers. 

Decrease with increase of contents PhOC mechanical parameters the block-copolyesters speaks redistribution of the relative contribution of plasticization and strengthening of intermolecular interaction (IMI) both in dmability, and in the module of elasticity. Thus it is important to note, that phosphinic an acid and phosphinoxyde at high contents render more effective complex influence on mechanical behavior of compositions rather high mechanical parameters and growth of the module of elasticity. General, though and in a different degree expressed, result - reduction b, and influence on parameters of plasticity of polymer. 

The plasticization of polymers by CO2, which causes a decrease in the glass-transition temperature (Tg) of the polymer, is another important feature that must be taken into accoimt. This plasticization facilitates the occurrence of important effects that are essential to polymer synthesis. Plasticization of the polymer allows enhanced diffusion of monomer and initiator into the polymer phase which often results in increased polymerization rates in heterogeneous polymerizations, removal of residual monomer, solvent, or catalyst from the polymer, and the formation of blends by polymerization within a CO2-swollen host polymer. An important emerging issue is the role that CO2 plays in manipulating the loci of reactants such as monomer/comonomer/initiator partition coefficients. Each of these topics is discussed in this chapter. 

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