Thermodynamic data such as heat capacity, enthalpy, entropy, Gibbs free energy and internal energy are very important for many engineering calculations which can be utilized in the design of different polymer processing equipment such as injection molding, extruder and compression molding. This book is aimed at the practicing engineer, as a comprehensive guide and reference source for solving material selection problems and resolving design issues where thermodynamics properties are possibly a factor. The book is divided into two main chapters. Each chapter is relatively independent and can be consulted without having to go through previous chapters. This book exhibits the thermodynamic properties of different polymers at different temperature (K). The thermodynamics properties included the enthalpy, entropy, internal energy and Gibbs free energy of polymeric materials and they were derivative from its heat capacity. This book helps to shed some light on thermodynamics data of polymers and it should be especially useful to professionals in polymer engineering and scientific research fields, or to anyone else who may be considering utilizing thermodynamics data of polymers.