نفود ترکیب تک و چند جزئی در رقیق سازی بینهایت در فونیک ایزوبوتیل

Single and multi-component diffusion at infinite dilution in polyisobutylene  

نفود ترکیب تک و چند جزئی در رقیق سازی بینهایت در فونیک ایزوبوتیل

ABSTRACT

In this study, diffusion coef®cients of acetone, benzene, chloroform, cyclohexane and methyl ethyl ketone (MEK) in polyisobutylene (PIB) have been measured at temperatures in the range 40± 70°C using capillary column inverse gas chromatography (CCIGC). The measured diffusion coef®cients for the PIB/MEK system, considered to be at in®nite dilution of the solvent, agree very well with those determined previously from gravimetric and spectroscopic techniques when extrapolated to the limit of zero MEK concentration. The Vrentas±Duda free-volume theory for diffusion is used to correlate the diffusivity data at in®nite dilution as a function of temperature, and the effect of solvent size on the diffusion process in PIB is studied. In addition, diffusion coef®cients of MEK/toluene and MEK/ethanol mixtures in PIB have been measured at 50°C. The CCIGC model for binary systems is used to determine diffusion coef®cients for each solvent individually over a wide range of mixture compositions. The resulting values are identical to those determined from pure component data, con®rming the hypothesis that the diffusion coef®cient at in®nite dilution is independent of a second in®nitely-dilute component, with or without solvation between mixture components.