Thermoforming : A Plastics Processing Guide, Second Edition

FROM THE FOREWORD Dr. Gruenwald has indicated the desirable properties of polymerics for differing applications; thus, his text is especially useful for polymer chemists who must ''tailor'' plastic materials for specific groups of applications. Engineers in extruding and calendering film and sheet will benefit from the intimate relationships elucidated between processing parameters imposed upon stocks employed in thermoforming and the products thereof. Mold designers are provided with a complete guide that will enable them to avoid the less obvious pitfalls and wasted effort so often experienced in the evolution of molds for (especially) complex parts.. Quite likely, Dr. Gruenwald's suggestions willl lead to considerable benefits to those who read and practice by this remarkable exposition of thermoforming technology. Robert K. Jordan Director-Metalliding Institute, Director-Engineering Research Institute, Scientist in Residence, Gannon University Content: Cover Half Title Title Page Copyright Page Table of Contents Foreword Preface 1: Introduction 2: Heating of the Plastic Means of conveying heat to the plastic Physics of radiation heating Thermal properties of plastics Heating equipment for plastic sheets Judging the correct temperature of the heated sheet Heater controls Clamping of sheets 3: Thermoforming Molds Reduction in wall thickness: male and female molds Computer-aided engineering for thermoforming Part shrinkage and dimensional tolerances Warpage Draft in the mold Surface appearance Mold materials Mold-cooling provisionsAir passage holes Increasing stiffness Mold plugs 4: Vacuum, Air Pressure, and Mechanical Forces Measuring vacuum and pressure forces Vacuum sources Vacuum accumulators or surge tanks Application of vacuum forces Pressure forming Mechanical forming 5: Cooling of Thermoformed Parts Means o f cooling the formed part Non-conventional cooling methods 6: Trimming of Thermoformed Parts Tools for trimming 7: Thermoforming Equipment Single-station thermoformer Shuttle thermoformer Rotary thermoforming equipment Continuous in-line thermoformers In-line thermoformerLinear thermoformers Pneumatic thermoformers Hydraulically operated thermoformers Mechanically operated thermoformers Skin packaging equipment Blister packaging equipment Snap packaging Vacuum packaging Packaging machinery Control mechanisms 8: Thermoforming-Related Material Properties Glass transition temperature Heat deflection temperature Softening range and hot strength Specific heat Thermal conductivity Thermal expansion Heat of fusion Thermal diftusivity Thermal stability Water absorption Orientation and crystallization Manufacture o f starting materialsCoextrusions and laminates Mechanical properties Material economics Regrind utilization 9: Thermoforming Materials' Chemical Descriptions Acrylics Cellulosics Polyolefins Styrene polymers Vinyl resins Engineering plastics Copolymers, blends, and alloys Fiber-reinforced thermoplastics Transparent materials Barrier materials Electrical properties Plastics recycling Flammability of plastics Toxicity of plastics 10: Thermoforming Processes Billow, bubble, or free forming Cavity forming Drape forming Plug-assist forming Billow drape forming Snap-back formingAir slip forming Reverse draw with plug-assist forming Trapped sheet pressure forming Twin-sheet forming Pressure forming Mechanical thermoforming Plug-and-ring forming or ridge forming Slip forming Matched-mold forming Rubber pad and fluid pressure or diaphragm forming Other thermoforming processes Adjusting process parameters Thermoforming troubleshooting guide 11: Design Considerations Assembly and bonding Snap-fits Mechanical bonding Forming around inserts Welding Solvent bonding Adhesive bonding Rigidizing thcrmoformed parts Bonding multiple parts "FROM THE FOREWORDDr. Gruenwald has indicated the desirable properties of polymerics for differing applications; thus, his text is especially useful for polymer chemists who must ""tailor"" plastic materials for specific groups of applications. Engineers in extruding and calendering film and sheet will benefit from the intimate relationships elucidated between processing parameters imposed upon stocks employed in thermoforming and the products thereof. Mold designers are provided with a complete guide that will enable them to avoid the less obvious pitfalls and wasted effort so often experienced in the evolution of molds for (especially) complex parts. Quite likely, Dr. Gruenwald's suggestions willl lead to considerable benefits to those who read and practice by this remarkable exposition of thermoforming technology. Robert K. Jordan Director-Metalliding Institute, Director-Engineering Research Institute, Scientist in Residence, Gannon University"--Provided by publisher. THERMOFORMING WILL ALWAYS represent only one part of all the possibilities for shaping plastics items, but the total market is so large that if only a fraction of it goes to thermoforming, sizeable business opportunities exist. THE VARIOUS THERMOFORMING processes are based on the recognition that rigid thermoplastics become pliable and stretchable when heated but will return to their original strength and rigidity when cooled. Indicates the desirable properties of polymerics for differing applications. This book is suitable for polymer chemists who must 'tailor' plastic materials for specific groups of applications.