In order to accurately demonstrate the material behavior during numerical simulation of thermoforming, the critical material parameters of any specific polymeric material need to be determined properly. In this study, acrylic sheets (Poly(methyl methacrylate), PMMA) of both opaque and transparent nature were chosen as the sample materials due to their widespread usage for the manufacturing of bathwares and kitchen appliances. Hyperelastic theory (e.g., Mooney-Rivlin and Ogden models) was employed with experimental verification to obtain the critical material parameters of PMMA. By conducting uniaxial tensile tests at elevated temperatures between 150 and 190degreesC and utilising the least square method (LSM), the major material parametric functions were derived in terms of forming temperature. Preliminary application on simulation of free inflation of a bubble profile resulted in promising agreement with the experimental data validating the developed parameters. (C) 2005 Springer Science + Business Media, Inc.