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This thesis describes a continuous extrusion process for manufacturing low-density, microcellular polystyrene foam sheets using carbon dioxide as a blowing agent. Microcellular polymer foams are characterized by a cell density greater than 10$\sp9$ cells/cm$\sp3$ and a cell size on the order of 10 $\mu$m. To date, most research on the continuous processing of microcellular polymer foams has focused on nucleation and cell growth phenomena. Little work has been done on their shaping aspect. Two extrusion systems; namely, a single-screw extrusion system and a tandem extrusion system with two die designs were used in this research. The systems were designed and analyzed based on an axiomatic design framework. Detailed design and construction of their components, which include an extruder screw for the second extruder, dies, a diffusion enhancing device, a heat exchanger, a cooling mandrel, and a take-up roll system, were carried out subsequently. Critical experiments were conducted to evaluate the performance of the systems. PS foam sheets with a cell density in the range of 10$\sp9$ to 10$\sp#x10;$ cells/cm$\sp3,$ a controlled volume expansion ratio in the range of 2.1 to 17.9, and a uniform sheet thickness were successfully obtained from the designed tandem foam extrusion system.
Combining the science of foam with the engineering of extrusion processes, Foam Extrusion: Principles and Practice delivers a detailed discussion of the theory, design, processing, and application of degradable foam extraction. In one comprehensive volume, the editors present the collective expertise of leading academic, research, and industry specialists while laying the scientific foundation in such a manner that the microscopic transition from a nucleus to a void (nucleation) and macroscopic movement from a void to an object (formation) are plausibly addressed. To keep pace with significant improvements in foam extrusion technology, this Second Edition: Includes new chapters on the latest developments in processing/thermal management, rheology/melt strength, and biodegradable and sustainable foams Features extensive updates to chapters on extrusion equipment, blowing agents, polyethylene terephthalate (PET) foam, and microcellular innovation Contains new coverage of cutting-edge foaming mechanisms and technology, as well as new case studies, examples, and figures Capturing the interesting evolution of the field, Foam Extrusion: Principles and Practice, Second Edition provides scientists, engineers, and product development professionals with a modern, holistic view of foam extrusion to enhance research and development and aid in the selection of the optimal screw, die design, and foaming system.
Why is it important to get to equilibrium and how long does it take? Are there problems running polypropylene profiles on a single screw extruder? Does the job involve compounding color concentrates on a corotating twin screw extruder? This unique reference work is designed to aid operators, engineers, and managers in quickly answering such practical day-to-day questions in extrusion processing. This comprehensive volume is divided into 7 Parts. It contains detailed reference data on such important operating conditions as temperatures, start-up procedures, shear rates, pressure drops, and safety. This reference is a practical guide to extrusion bringing together both the equipment and materials processing aspects. It provides basic and advanced topics about the thermoplastics processing in the extruder, for reference and training. Parts 1 û 3, emphasize the fundamentals, for operators and engineers, of polymeric materials extrusion processing in single and twin screw extruders. Parts 4 û 7 treat advanced topics including troubleshooting, auxiliary equipment, and coextrusion for operators, engineers, and managers. Extensive applications in Part 7 cover such contemporary areas as compounding, blown film, extrusion blow molding, coating, foam, and reprocessing. Each chapter includes review topics.
Combining the science of foam with the engineering of extrusion processes, Foam Extrusion: Principles and Practice delivers a detailed discussion of the theory, design, processing, and application of degradable foam extraction. In one comprehensive volume, the editors present the collective expertise of leading academic, research, and industry spec
This handbook provides an exhaustive description of polyethylene. The 50+ chapters are written by some of the most experienced and prominent authors in the field, providing a truly unique view of polyethylene. The book starts with a historical discussion on how low density polyethylene was discovered and how it provided unique opportunities in the early days. New catalysts are presented and show how they created an expansion in available products including linear low density polyethylene, high density polyethylene, copolymers, and polyethylene produced from metallocene catalysts. With these different catalysts systems a wide range of structures are possible with an equally wide range of physical properties. Numerous types of additives are presented that include additives for the protection of the resin from the environment and processing, fillers, processing aids, anti-fogging agents, pigments, and flame retardants. Common processing methods including extrusion, blown film, cast film, injection molding, and thermoforming are presented along with some of the more specialized processing techniques such as rotational molding, fiber processing, pipe extrusion, reactive extrusion, wire and cable, and foaming processes. The business of polyethylene including markets, world capacity, and future prospects are detailed. This handbook provides the most current and complete technology assessments and business practices for polyethylene resins.
Foaming with Supercritical Fluids, Volume Nine provides a comprehensive description of the use of supercritical fluids as blowing agents in polymer foaming. To this aim, the fundamental issues on which the proper design and control of this process are rooted are discussed in detail, with specific attention devoted to the theoretical and experimental aspects of sorption thermodynamics of a blowing agent within a polymer, the effect of the absorbed blowing agent on the thermal, interfacial and rheological properties of the expanding matter, and the phase separation of the gaseous phase, and of the related bubble nucleation and growth phenomena. Several foaming technologies based on the use of supercritical blowing agents are then described, addressing the main issues in the light of the underlying chemical-physical phenomena. Offers strong fundamentals on polymer properties important on foaming Outlines the use of supercritical fluids for foaming Covers theoretical points-of-view, including foam formation of the polymer/gas solution to the setting of the final foam Discusses the several processing technologies and applications
The current energy debate considerably affects science, economy and politics. A key aspect of this discussion is energy saving by improvement of thermal insulations for buildings. In this regard, nano insulation materials (NIMs) are the insulation materials of the future. If additionally, a pore size reduction to nanoscale results in optical transparency, completely new markets for polymer foams will arise. However, the realization of these high-potential materials is accompanied by many challenges, as for example the extremely high interfacial tension emerging during foaming processes that cause an undesired coarsening of the foam structure. To overcome these challenges, new strategies and templates have to be scientifically developed. Moreover, it is crucial to understand the foaming in detail. In this context the early state of foaming was studied by means of the principle of supercritical microemulsion expansion (POSME). The benefit of using microemulsions containing a super- or near-critical fluid as oil component is the thermodynamic stability at high pressures. This allows a fast repeatability of the expansion process at nanoscale by applying pressure cycles. In combination with a specially designed stroboscopic high pressure cell, the structural processes could be observed by time resolved small angle neutron scattering experiments. It turned out that the addition of a low molecular oil as anti aging agent results in a deceleration of foam coarsening during expansion by more than an order of magnitude. Parallel to these studies, the nanofoams by continuity inversion of dispersions (NF-CID) principle was utilized for the preparation of nanoporous polymeric materials. The significant innovation of the NF-CID principle is the generation of an extremely high number density of propellant pools by a continuity inversion of a CO2-soaked colloidal crystal, i.e. the formerly discrete polymer nanoparticles convert into a homogeneous matrix with nanodisperse fluid inclusions, if the temperature is raised above the glass transition of the respective polymer. Expanding those templates by applying a specific set of parameters led to polymethylmethacrylate and polystyrene nanoporous materials that feature pore sizes smaller than 100 nm.