Plasticizers plasticizer interactions

The arrangement of polar groups may be more significant if internal hydrogen bonding can occur. If there is a strong interaction of this type, compatibility decreases, because plasticizer-plasticizer interaction is preferred over plasticizer-polymer interaction (tri-cosane is five times more soluble in butanol than in ethanol). 

The mechanistic explanation of plasticization [11] looks at the interactions of the plasticizer with the polymer. It assumes that the plasticizer molecules are not permanently bound to the resin molecule but are free to self-associate and to associate with the polymer molecule at certain sites, then disassociate. As these interactions are weak, there is a dynamic exchange process whereby as one plasticizer molecule becomes attached at a site or center, it is rapidly dislodged and replaced by another. Different plasticizers will yield different plasticization effects because of the differences in the strengths of the plasticizer-polymer and plasticizer-plasticizer interactions. At low plasticizer levels, the plasticizer-PVC interactions are the dominant interactions while at high plasticizer concentration ranges, plasticizer-plasticizer interactions become more important. 

Unlike incompatible heterogeneous blends of elastomer-elastomer, elastomer-plastic, and plastic-plastic, the reactively processed heterogeneous blends are expected to develop a variable extent of chemical interaction. For this reason the material properties, interfacial properties, and phase morphology of reactively processed blends would differ significantly from heterogeneous mixtures. 

Plasticization has been explained by a variety of theories in an attempt to explain how the plasticizer reduces the rigidity of the final part. All theories rely on the premise that the plasticizer reduces the strength of the intermolecular forces between the polymer chains. The theories fall into two broad categories interference mechanisms and expansion mechanisms. The interference mechanisms state that plasticizer molecules interact only weakly with the polymer chains after separating the chains from one another, thereby reducing the overall cohesion of the material. The expansion mechanisms state that the reduced rigidity arises from an increase in the free volume of the system as the system expands to incorporate bulky,... 

M. Dadfamia, P. Sofronis, I. M. Robertson, and B. P. Somerday, Hydrogen/Plasticity Interaction at Internal Cracks in Pipeline Steels, Seventh International ASTM/ESIS Symposium on Fatigue and Fracture, Tampa, Florida, USA, November 2007. 

However, it is also important to consider the intermolecular forces between the plasticizer molecules themselves and between plasticizer and polymer. Unless all these interactions-i.e., plasticizer-plasticizer, plasticizer-polymer, and polymer-polymer-are the same order of magnitude, there can be no plasticizing action. 

The specific contribution of B in the DBB-value can be taken into account by two supplementary dimensionless parameters. While psB stands for a structural difference of B in comparison to a hypothetical n-alkane with the same relative molecular mass MrB, the number pBB = pBP + pJ)p/T represents an interaction increment between B and P, due to the different polarities of the solute and plastic. This interaction is generally a function of temperature. The two parameters, pvB and pBB can be considered as relative mass increments (positive or negative) which vanish in the reference system of n-alkanes in polymethylene. 

Sometimes a polymer is too stiff and brittle to be useful in many applications. In this case, a low molecular weight compound called a plasticizer is added to soften the polymer and give it flexibility. The plasticizer interacts with the polymer chains, replacing some of the intermolecular... 

Semenova SI, Ohya H, and Smirnov SI. Physical transitions in polymers plasticized by interacting penehant. J Membr Sci 1997 136 1-11. 

Semenova SI, Smirnov SI, and Ohya H. Performances of glassy polymer membranes plasticized by interacting penetrants. J Membr Sci 2000 172 75-89. 

Sakellariou, P. Hassan, H. Rowe, R.C. Plasticization and interactions of polyethylene glycol 6000 with hydroxy-propyl methylcellulose/polyvinyl alcohol blends. Int. J. Pharm. 1994, 102, 207-211. 

Even less is known about ionomer/plasticizer interactions on a molecular level. A variety of scattering and spectroscopic techniques that can probe this level have been mentioned, but they have been applied primarily to the specific case of water in ionomers, and in particular to hjdrated perfluorinated ionomers. At the least, these studies demonstrate the powerful potential of the techniques to contribute to a more complete understanding of structure-property relationships in plasticizer/ionomer systems. For e.xample, to return to the question of the effect of nonpolar plasticizers on the ionic domains how can the decrease in the ionic transition temperature be reconciled with the apparently minimal effect on the SAXS ionomer peaks and with the ESR studies that indicate (not surprisingly) tiiat these plasticizers have essentially no influence on the local structure of the ions Is it due to their association with the hydrocai bon component of the large aggregates or clusters Or if these entities do not exist, as some researchers postulate, what is the interaction between the nonpolar plasticizer, the hydrocarbon component and the ionic domains These questions are, of course, intimately related to the understanding of ionomer microstructure even in the absence of plasticizer. The interpretation of SAXS data in particular is subject to the choice of model used. 

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