The Study Of Phase Equilibrium For EG-SCCO₂-PET Ternary Syetem

Removal of the volatile components from the polymer melt or solution has become a very important polymer processing operation.These small molecular volatiles mainly include byproducts,solvents and other unreacted impurities.Some residual monomers are carcinogenic to humans when polymeric materials are used in food or medicine packaging.The accumulation of residual monomers inhibits the forward reaction,and then hinders the increase of molecular weight.Therefore,these residues should be removed from polymers and this progress was known as devolatilization.The traditional latent-heating method has a low devolatilization efficiency.Supercritical fluid(SCF)technology is a green sustainable developing technology for its unique physiochemical property with liquid-like densities and gas-like diffusivities,and has been widely used in petrochemical,food,medicine,bio-chemical,material science,environmental protection etc.SCF technology has been applied in the study of polymer devolatilization and good results were obtained.In order to design or optimize the volatilization processing with the supercritical fluid assisted,it is necessary to have a deeply understand about the solubility of residual monomers in supercritical fluids,phase equilibrium of solute-supercritical fluid-polymers ternary system,diffusion of solute in monomers,etc.Nowadays,there have been some researches about solute solubility in supercritical fluids are discussed,but study refers to phase equilibrium of solute-supercritical fluid-polymers ternary system and diffusion of solute in polymer monomers is little reported.In this paper,the high pressure apparatus is used to measure the partition coefficient of ethylene glycol between supercritical carbon dioxide andpolyethylene terephthalate with static method when the ethylene glycol-supercritical cardon dioxide-polyethylene terephthalate ternary system in phase equilibrium.Experimental data are correlated with state equations of Sanchez-Lacombe model.The aim of this paper is to provide some basic data for the development of supercritical fluid assisted polymer devolatilization.The experimental results show:(1)the partition coefficient increases with the increase of temperature;(2)pressure in the range of 9 to 17 MPa(1)the partition coefficient with the increase of the pressure decreases first and then increases when T<70℃(2)the partition coefficient with the increase of pressure increased first and then decreased when T≥70℃...