Disclosed is a process for improving the rate of solid state polymerization of ethylene terephthalate polymers or copolymers comprising copolymerizing terephthalic acid or dimethyl terephthalate and ethylene glycol with 2-10 mol % diethylene glycol and 0.1-10 mol % cyclohexanedimethanol to form a prepolymer, forming solid particles from the prepolymer, and solid state polymerizing the particles at a temperature between the glass transition temperature and melting point of the particles until a predetermined I.V. is reached.
