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Abstract: Polymer foams are used extensively in a variety of applications. A firm understanding of bubble nucleation is vital to predict foam properties based on process conditions. However, a number of theoretical and experimental challenges have thus far limited progress in this area. The use of a scaling theory is proposed to connect nucleation behavior to well understood bulk phase behavior of polystyrene-CO2 systems, which can be predicted by equations of state, such as the Sanchez-Lacombe or Statistical Associating Fluid Theory equation of state. Scaling theory of nucleation asserts that when the reversible work of critical nucleus formation is properly normalized and plotted against the normalized degree of supersaturation, the resulting scaling curve is insensitive to temperature and the materials being used. Once the form of the scaling function is known, it can be used to predict the nucleation barrier knowing only the initial foaming conditions and calculating only bulk thermodynamic values. Using an extension of diffuse interface theory, the slope of the scaling curve near saturation was determined. This initial slope constrains the scaling function for better predictions of the reversible work. The accuracy of the scaling theory was examined by comparison to experiments. The scaled free energy barriers determined from experiments are consistent with the scaling function so constructed, and the theoretical results qualitatively agree with those found previously.
This book is the inaugural volume a series entitled Polymeric Foams: Technology and Applications. Generally, thermoplastic and thermoset foams have been treated as two separate practices in industry. Polymeric Foams: Mechanisms and Materials presents the basics of foaming in general build a strong foundation to those working in both thermoplastic a
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 reviews the chemistry, manufacturing methods, properties and applications of the synthetic polymer foams used in most applications. In addition, a chapter is included on the fundamental principles, which apply to all polymer foams. There is also a chapter on the blowing agents used to expand polymers and a chapter is on microcellular foams - a relatively new development where applications are still being explored.
For phenomena involving bubble nucleation, the molecular cluster model is used to predict the tensile strength and superheat limit of liquids and the amount of decompression for gaseous bubble nucleation in supersaturated solutions. The book investigates various gaseous bubble nucleation events including the bubble formation in gas-water solutions, CO bubble formation in iron melts, the formation of microcellular foams in polymers, the nucleation of nano-sized H2O bubbles in rhyolite melts, and bubble nucleation in shear flow fields. The book also investigates vaporous bubble nucleation events such as bubble formation on a cavity-free surface and inside a solid nanopore in 3M NaCl solution, superheat limit of liquids, and bubble nucleation near the absolute zero temperature by quantum tunnelling in liquid helium. For bubble dynamics phenomena, a set of homologous solutions of the Navier-Stokes equations for evolving spherical bubbles are used to treat gaseous bubble growth in organic solutions, polymer solutions, and in viscous rhyolitic melts. The growth and collapse of laser-induced vapor bubbles in liquid, and on solid particles is discussed as an example of homologous motion of the spherical object. Sonoluminescence phenomena in water and in sulfuric acid solutions, the pressure and shock wave propagation in bubbly mixtures, the gravitational collapse of Newtonian stars, and the core collapse of supernovas are also treated using these homologous solutions. The motion of a fire-ball generated by a TNT explosion underwater is obtained using a zero gravitational constant in the equation of motion for Newtonian stars.
Multiphase Flow in Polymer Processing focuses on dispersed and stratified multiphase flow in polymer processing. This book explores the rheological behavior of multiphase (or multicomponent) polymeric systems as they are involved in various fabrication operations. It also outlines the importance of the morphological states of multiphase polymeric systems to explain the systems, rheological behavior in the fluid state, and mechanical behavior in the solid state. This monograph consists of eight chapters divided into two parts. After discussing dispersed and stratified multiphase flow in polymer processing, it introduces the reader to the fundamentals of rheology. The following chapters focus on the rheological behavior of particulate-filled polymeric systems and heterogeneous polymeric systems; the phenomenon of droplet breakup in dispersed flow; and gas-charged polymeric systems. The role of the discrete phase (that is, solid particles, liquid droplets, gas bubbles) in determining the bulk rheological properties of the multiphase system is highlighted, along with some representative polymer processing operations (namely, fiber spinning and injection molding) of the multiphase (or multicomponent) polymeric systems. Coextrusion in cylindrical, rectangular, and annular dies is also considered. The final chapter is devoted to the phenomenon of interfacial instability in coextrusion. This text will be a useful resource for chemists, chemical engineers, and those in the polymer processing industry.
Polymers are among the major hallmarks of 20th-century science, and the explosive outgrowth and tremendous importance of polymeric foams is a testament to their amazing versatility and unique properties. With applications from automotive to acoustic and medical, polymeric foams pervade all areas of our lives. If this growth is to continue into the new millennium, especially in light of stringent environmental regulations, a strong understanding of the basic science and the major technologies behind foam production is critical. Written by experienced and accomplished leaders in the field, Polymeric Foams: Science and Technology provides comprehensive coverage of the fundamentals, technologies, applications, and recent developments. The authors first outline the basic principles and fundamental foaming mechanisms, covering thermodynamics, kinetics, and the basics of blowing agents and foam formation. Foaming technologies and product applications then become the focus, with explanations of structure-property relationships, processing methods, and general types of foams. The book concludes with chapters on recent developments in composite and biodegradable foams that illustrate how to tailor processing to meet application needs. Illuminating the role of polymeric foams in the modern materials landscape, Polymeric Foams: Science and Technology is the perfect guide for developing innovative materials that achieve better performance and regulatory compliance.