Mechanism of plasticizer action

Chemical Engineering Department, Alicante University, Spain 

In spite of plasticizers being used since the XIX centuiy, the theories about plasticization were not developed until the years 1930 to 1950. These earUer theories could not explain adequately all the phenomena involved during plasticization, but they provided an interesting picture of the process. Probably due to this fact and to their simplicity and easy comprehension that these classical theories have been used for mai years, and in some cases are still being used. Recently, with the development of computational methods, some new quantitative models on plasticization have been proposed. 

There are a few published monographs which collect the theories on plasticization in a more or less exhaustive way. Among them it is worth mentioning the books by Doohttle and by Ritchie. Chapter 2 from The Technology of Plasticizers by Sears and Darby is undoubtedly the most valuable review of all the plasticization theories developed until the book was written. 

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 

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Steps 3 and 4, however, can be described as chemical plasticization since the rate at which these processes occur depends on the chemical properties of molecular polarity, molecular volume, and molecular weight. An overall mechanism of plasticizer action must give adequate explanations for this as weU as the physical plasticization steps. 

Spectral properties of plasticizers are useful in various studies, especially in helping to understand various aspects of the mechanism of plasticizer action. " Table 10.1 shows typical IR absorption peaks by representatives of major groups of plasticizers. 

The special attention is given to the mechanism of plasticizers action in segmented polyrrrethanes and perspectives of plasticizers application for regulating properties of polyrrrethane compositions. 

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