Modeling of Solid-State Polymerization of Poly(ethylene terephthalate): Comparison of Finite Element and Finite Difference Methods

Poly(ethylene terephthalate) (PET) is one of the most important engineering thermoplastics because of its unique properties such as excellent clarity, thermal and mechanicalproperties, dyeability, dimensional stability and good barrier properties against diffusion of oxygen and carbon dioxide.Solid-state polymerization (SSP) is an important process to increase molecular weight of PET for injection or blowmolding applications. Generally, SSP is carried out by heatingPET prepolymer to a temperature above its glass transition temperature and below its melting point. Esterification andpolycondensation are the two main reactions occurring during SSP. Ethylene glycol (EG) and water, as byproducts, are released from these two reactions. They are removed to enhance the forward reaction rate either by allowing an inert gas flow or by applying vacuum. In this work the SSP of PETwas modeled using finite element and finite difference methods