A composition for forming an article having an improved resistance to hydrolysis is disclosed. The composition comprises a polyalkylene terephthalate and/or polyester thereof, a triglyceride, an epoxy component, and a plasticizer. The polyalkylene terephthalate has terminal carboxyl groups and hydroxyl groups and internal ester linkages. The triglyceride has at least one acid component with 6 to 30 carbon atoms and at least one epoxy group for reacting with the carboxyl groups. The epoxy component has internal aromatic groups and at least one terminal epoxy group for reacting with the carboxyl groups. The plasticizer comprises an esterification product of a polyoxyalkylene glycol with 1 to 20 carbon atoms and an aliphatic carboxylic acid with 1 to 25 carbon atoms for improving melt flow properties and for reducing hydrolysis of the composition.