An Analytical Equation of State Extended to Copolymers

An analytical equation of state (EOS) entitled Ihm-Song-Mason (ISM) has been previously employed to calculate some thermodynamic properties of molten polymers including specific volume and isothermal compressibility (S.M. Hoseini, Physical Chemistry & Electrochemistry, 2 (2014) 56-65). This work extended that EOS to predict the volumetric properties of some molten ethylene copolymers including ethylene/1-octene, ethylene/1-butene (xethylene equal to 0.8543 and 0.563), ethylene/propene. The ability of the extended EOS was checked by comparing the results with 738 literature data points for the specific volumes over the temperature range from 422.35-505.89 K and pressure range from 0.1 up to 200 MPa. The average absolute deviation (AAD) of the calculated specific volumes from literature data was found to be 1.12%. The isothermal compressibility coefficients, κT have also been predicted using ISM EOS. From 180 data points examined, the AAD of estimated κT was equal to 8.48%. Our calculations on the volumetric and thermodynamic properties of studied copolymers reproduced the literature data with reasonably good accuracy.