Modified Method to Polyethylene Terephthalate Carboxyl End Groups Determination

The Polyethylene terephthalate (PET) is engineering thermoplastic and made via condensation polymerization reaction of terephthalic acid and ethylene glycol. Properties ofPET are related to molecular structure. Carboxyl end groups are chemical group results of non reactants terephthalic acidic groups in the polymer chains ends situation [1]. PET carboxyl end groups number can be used to identify the polymers properties. It also can be used to predication the thermaldegradation of polymer in the polymerization process, polymer average molecular weight estimation and thepolymerization process control. Properties and hydrolysisresistance of PET is dependent on carboxyl end groups content, thereby reducing the concentration of PET carboxylend groups cause increase on the polymer hydrolysis resistance [2-6]. The main disadvantage of conventional potentiometric method in determination of carboxyl end group concentration is toxicity of solvent. Also, direct titration method with safe solvents like benzyl alcohol shows nonrepeatable and without accuracy result. Attempt has been made in this research to present the safe and accurate method for calculating the PET carboxyl end group concentration