聚乙烯吡咯烷酮不同温度下的密度和粘度

Measurement and correlation of density and viscosity of polyvinylpyrrolidone solutions in alcohols at different temperatures

Mohammed Taghi Zafarani-Moattar a,*,Zh.Khoshsima b

a Physical Chemistry Department,University of Tabriz,Tabriz,Iran

b

Department of Physical Chemistry,Payame Noor University,Tabriz,Iran

a r t i c l e i n f o Article history:

Received 14May 2008

Received in revised form 11June 2008Accepted 24June 2008

Available online 1July 2008Keywords:Density

Apparent specific volume Viscosity

Polymer solutions Eyring-NRTL model

a b s t r a c t

The density and viscosity values of (polyvinypyrrolidone +methanol,+ethanol,or +1-propanol)solu-tions have been measured at T =(298.15,308.15,and 318.15)K.Apparent specific volume and partial specific volume of the polymer and solvent have been computed from the experimental values.Apparent specific volume values have been correlated with the suitable polynomial equations.A simple exponen-tial equation and Eyring-NRTL viscosity model in the modified form have adequately been used for the correlation of the viscosity values.

Ó2008Elsevier Ltd.All rights reserved.

1.Introduction

Thermodynamic properties of polymer solutions are important for understanding solute–solvent and solute–solute interactions.Knowledge of volumetric properties of polymer solutions has been proven to be a very useful tool in evaluating the structural interac-tions occurring in these solutions [1–4].Knowledge of the viscosity of polymer solutions is important for practical and theoretical pur-poses.The viscosity of polymer solutions provides an invaluable type of data in polymer research,development and engineering.Furthermore,the simultaneous investigation of viscosity,and vol-ume effects on mixing can be a powerful tool for the characteriza-tion of the intermolecular interactions present in these mixtures.Also,knowledge of the dependence of viscosities of polymer solutions on composition is of great interest from a theoretical standpoint,since it may lead to better understanding of the funda-mental behaviour of polymer solutions.Many research groups have focused their attention on obtaining information on the ther-modynamics of aqueous polyethylene glycol (PEG),which is often used in biotechnology.In this respect,thermodynamic properties such as (vapour +liquid)equilibrium,density,and viscosity have been obtained [1–4].However,similar information on the thermo-dynamics of aqueous solutions of polyvinylpyrrolidone (PVP),which is also a very important system with respect to its use in

biotechnology,is scarce.An attempt has been made to obtain infor-mation on the hydration of PVP by measuring viscosity,density and heat of solution of aqueous solution of PVP;however,the cor-responding data are limited to T =298.15K and has been given in graphical form [5].Recently some results for density and water activity have been provided by Kany et al .[6]at T =(278.15,293.15,and 303.15)K.These authors [6]obtained some other ther-modynamic properties using the techniques of Laser-Light scatter-ing and membrane osmometry.Densities,viscosities,and water activities of aqueous solutions of polyvinylpyrrolidone were deter-mined experimentally at T =(298.15,308.15,318.15,and 328.15)K in our previous work [7].

In this work,densities and viscosities of polyvinylpyrollidone solutions in alcohols (methanol,ethanol,and 1-propanol)have been determined experimentally at T =(298.15,308.15,and 318.15)K,from which apparent specific volume and partial spe-cific volume of polymer and solvent,have been computed.Appar-ent specific volume values have been correlated with the suitable polynomial equation.The Eyring-NRTL viscosity model in the mod-ified form and simple exponential equation have adequately been used for the correlation of the viscosity values.2.Experimental 2.1.Materials

The PVP (average molar mass of 10,000)was obtained from Applichem.Methanol (minimum mass fraction purity 0.998),

0021-9614/$-see front matter Ó2008Elsevier Ltd.All rights reserved.doi:10.1016/j.jct.2008.06.013

*Corresponding author.Fax:+984113340191.

E-mail address:zafarani47@ (M.T.Zafarani-Moattar).J.Chem.Thermodynamics 40(2008)

1569–1574

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