Rheological Modeling for Production of High Quality Polymeric
The fundamental defect inherent to the thermoforming technology is wall-thickness variation of the products due to inadequate thermal processing during production of polymer. A nonlinear viscoelastic rheological model is implemented for developing the process model. This model describes deformation process of a sheet in thermoforming process. Because of relaxation pause after plug-assist stage and also implementation of two stage thermoforming process have minor wall-thickness variation and consequently better mechanical properties of polymeric articles. For model validation, a comparative analysis of the theoretical and experimental data is presented. Keywords—High-quality polymeric article, Thermal Processing, Rheological model, Minor wall-thickness variation.
Wall thickness distribution in thermoformed food containers produced by a Benco aseptic packaging machine
Effects of process parameters such as forming temperature, forming air pressure and heating time on wall thickness distribution in plug-assist thermoformed food containers using multilayered material were investigated. Multilayered rollstock-base material formed into containers by thermoforming process using a Benco aseptic packaging machine. Forming temperatures in the range of 131-170°C, air-forming pressures of 2, 3, 3. 5 and 4 bars, and heating times of 66, 74, 84, 97 and 114 seconds were used in the thermoforming process. Analysis of wall thickness data obtained for the thermoforming parameters used in this study showed that wall thickness was significantly affected by forming temperature, pressure and heating time at 0.05 significance level. Besides the processing parameters, wall location, container side, and their interactions significantly affected wall thickness. Forming temperature was found to be the principle parameter influencing wall thickness distribution in a plug-assist thermoforming operation. The optimum operating conditions of the packaging machine for the thermoforming process are: 146-156°C for forming temperature, 2-4 bars for air-forming pressure and 74-97 seconds for heating time.
Positive Rights and State Constitutions: The Limits of Federal Rationality Review
INTRODUCTION ............................................................................................................................. 1132 I. STATE CONSTITUTIONAL WELFARE PRACTICE ............................................................. 1144 A. A Mandatory Obligation: The New York Example .................................................. 1144 B. A Typology of Current State Court Decisions .......................................................... 1145 IT. RECONSIDERING FEDERAL RATIONALITY REVIEW IN STATE CONSTITUTIONAL WELFARE CASES ................................................................................ 1153 A. Rationality Review and Positive Rights .................................................................. 1155 B. Rationality Review and Democratic Legitimacy .................................................... 1157 C. Rationality Review and Judicial Finality ............................................................. xi61 D. Rationality Review and Federalism ......................................................................... i166 E. Rationality Review Revisited .................................................................................... 1169 III. TOWARD A NEW STANDARD OF REVIEW ......................................................................... 1169 A. The Need for Judicial Review .................................................................................. 1170 B. Institutional Competence and Welfare Litigation ................................................... 1175 I. State Courts as Fact Gatherers ......................................................................... 1175 2. State Courts as Policymakers ......................................................................... " 179 3. State Courts as Rights Enforcers ..................................................................... 1182 C. A Jurisprudence of Consequences .............................................................................. 1183 D. Why Education and Not Welfare? ........................................................................... i86 E. Implications for Welfare Litigation ........................................................................... i9i IV. CONCLUSION ........................................................................................................................ 1194