Download or read book Extrusion Processing of Low bulk Density Microcellular Open cell Thermoplastic Foams written by Chang-Dong Patrick Lee and published by . This book was released on 2006 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to promote a deeper understanding of the cell opening behavior during foaming, a failure analysis of a cell wall was performed according to the Considere and Failure criteria using the uniaxial experimental data of a polymer melt. A theoretical approach to prediction of the cell wall rupture moment was proposed using two adjacent cubic-shaped cells. This concept was further extended to arrive at an estimation of the minimum threshold diameter of a foam extrudate to produce an open-cell foam structure. A continuous extrusion process for the manufacture of low-density, microcellular, open-cell thermoplastic foams is presented using a single-screw tandem extrusion foaming system. Fundamental studies have been conducted to investigate the effects of various processing parameters and materials compositions on the basic properties (i.e., extensional behavior, solubility, diffusivity, and initial foam extrudate shape) of plastic melts and melt/gas solutions that influence the cell morphologies of thermoplastic foams. The observed phenomena were essential in understanding and devising the processing strategies to achieve a desired foam structure. Based on the fundamental studies, this thesis presents the basic strategies for promoting a low-density, microcellular, open-cell thermoplastic foam. The effects of polymer blending, additives, processing temperature, blowing agent content, die geometry, and surface quenching on the final foam morphologies were thoroughly investigated to verify the proposed strategies. By tailoring the material compositions and processing conditions, low-density (>10 fold), microcellular (109 cells/cm 3), open-cell (>95%) thermoplastic foams were successfully achieved. Furthermore, a procedure for estimating gas loss from a foam structure was proposed in order to understand the effect of gas loss during open-cell content measurement using a gas pycnometer, and the corresponding open-cell content errors were calculated.
Download or read book Foam Extrusion written by S.-T. Lee and published by CRC Press. This book was released on 2014-04-07 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Download or read book Extrusion Processing for Manufacture of Low density Fine celled Polypropylene Foams written by Hani E. Naguib and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A continuous extrusion process for the manufacture of low-density, fine-celled polypropylene foams is presented. Due to its outstanding functional characteristics and low material cost, polypropylene foams have been considered as a substitute for other thermoplastic foams in industrial applications. However, only limited research has been conducted on the production of polypropylene foams because of the weak melt strength, and no research has been conducted to investigate the mechanisms that govern the expandability of polypropylene foams. This thesis presents the effective strategies for increasing the volume expansion ratio as well as the mechanisms governing the foam density of polypropylene foams. The basic strategies taken in this study for the promotion of a large volume expansion ratio of polypropylene foams are: (a) to use a branched material for preventing cell coalescence; (b) to use a long-chain blowing agent with low diffusivity; (c) to lower the melt temperature for decreasing gas loss during expansion; and (d) to optimize the processing conditions in the die for avoiding premature crystallization. The effects of processing and materials parameters on the foam morphologies of polypropylene materials were thoroughly studied using a single-screw tandem foam extrusion system. A careful analysis of extended experimental results obtained at various processing conditions indicates that the final volume expansion ratio of the extruded polypropylene foams blown with butane is governed either by loss of blowing agent or by crystallization of the polymer matrix. By tailoring the processing conditions in the die, ultra low-density, fine-celled polypropylene foams with very high expansion ratio up to 90-fold were successfully produced from the branched polypropylene resins. Fundamental studies have also been conducted to investigate the effect of various processing and materials parameters on the thermodynamic, thermal and melt fracture behaviors of polypropylene melts with foaming additives that influence the cell morphology of polypropylene foams.
Download or read book Thermoplastic Foam Processing written by Richard Gendron and published by CRC Press. This book was released on 2004-10-28 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: As researchers seek replacements for banned, ozone-depleting foaming agents, the authors of Thermoplastic Foam Processing: Principles and Development strive to develop a better understanding of foaming processes and find solutions for day-to-day practice. This book presents the latest research in foam extrusion and physical foaming agents with a st
Download or read book Thermoplastic Foam Extrusion written by James L. Throne and published by Hanser Gardner Publications. This book was released on 2004 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique introduction covers both low- and high-density thermoplastic foams in an easy-to-follow style that avoids excursions into the theoretical aspects of foam processing.
Download or read book Extrusion Processing for Manufacture of Low density Microcellular Polycarbonate Foams Uing CO 2 microform written by John W. S. (John Won S.) Lee and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2004 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the effective strategies for increasing the volume expansion ratio and the cell density of polycarbonate foams. The basic strategies are: (a) to use sufficiently high pressure all through the extrusion system; (b) to use branched material; (c) to use high pressure drop rate at the die exit; (d) to use sufficiently high contents of CO 2; (e) to optimize the processing temperature. The effects of processing and material parameters on foam morphologies were thoroughly studied using a single-screw tandem foam extrusion system. By tailoring the processing and material parameters, polycarbonate foams with an expansion ratio of up to 19 times with a cell density over 1010 cells/cm3 were successfully produced. A continuous extrusion process for the manufacture of low-density microcellular polycarbonate (PC) foams using CO2 is presented. Due to its outstanding mechanical properties and high thermal resistance, polycarbonate foams have been considered as a candidate that will broaden the applications of foams in new industrial areas with high temperature environments.
Download or read book Development of Microcellular Foam Sheet Extrusion Systems written by Anthony Kwok-Fu Yeung and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Polymeric Foams written by Shau-Tarng Lee and published by CRC Press. This book was released on 2008-12-24 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explores the Latest Developments in Polymeric FoamsSince the 1960s polymeric foams have grown into a solid industry that affects almost every aspect of modern life. The industry has weathered the energy crisis in the 70s, ozone issues in the 80s, and recycle/reuse in the 90s. However, the pace of development and social climate is rapidly changing a
Download or read book SPE ANTEC 1999 Proceedings written by Spe and published by CRC Press. This book was released on 1999-04-29 with total page 1430 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume 2 of the conference proceedings of the SPE/Antac on 'Plastics Bridging the Millennia- subtopic of 'Materials', held on the 2-6 May 1999 in New York City, USA.
Download or read book Extrusion Processing of Low density Microcellular Foams written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Extrusion Processing of Low density Microcellular Foams microform written by Amir Hossein Behravesh and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Foaming Thermoplastics written by Pieter Spitael and published by . This book was released on 2003 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Research inPolymerization written by Nevin Çankaya and published by BoD – Books on Demand. This book was released on 2018-01-17 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this book is to help you concentrate on recent developments in polymerization. The chapters collected in the book are contributions by invited researchers with a long-standing experience in different research areas. I hope that the material presented here is understandable to a broad audience, not only chemists but also scientists from various disciplines. The book contains nine chapters in three sections: (1) "General Information about Polymerization," (2) "Biomaterial Content Polymer Composites," and (3) "Mechanical Properties of Polymerization." The book provides detailed and current reviews in these different areas written by experts in their respective fields. This book is expected to be useful for polymer workers and other scientists alike and contribute to the training of current and future researchers, academics, PhD degree students, as well as other scientists.
Download or read book Porous Cellular and Microcellular Materials written by American Society of Mechanical Engineers. Materials Division and published by . This book was released on 1998 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Manufacturing Highly Expanded Thermoplastic Polyurethane Foams Using Novel Injection Molding Foaming Technologies written by Hrishikesh Ashokrao Kharbas and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis summarizes the studies undertaken to achieve the objective of manufacturing injection-molded thermoplastic polyurethane (TPU) foams with high density reductions, desir-able microstructures, and customizable properties. TPU foams are quickly gaining market share in numerous applications in the sports and recreation as well as manufacturing industries. This is because TPU foams can be easily manufactured in a variety of densities, hardnesses, and mechanical properties, ranging from highly resilient to highly compressible foams, with different processing methods, such as injection molding, casting, and extrusion. Typically, TPUs are being foamed to a minimum density of 0.40 g/cm3 (400 kg/m3). It is the aim of this thesis to expand the understanding and processing knowledge of manufacturing TPU foams with densities as low as 0.25 g/cm3 (250 kg/m3), while maintaining desirable microstructures. It is also an aim of this thesis to develop a novel process to control foam properties locally in injection molded TPU foams. In the journey toward achieving the aforementioned objectives, five studies were conducted and are presented in this manuscript. An experimental study evaluating the CBA and PBA foaming of TPU has been undertaken. A novel foam injection molding process using CO2 + N2 as co-blowing agents to exploit the synergistic benefits of co-blowing agents was also evaluated in this study. It was found that PBA foaming can be vastly advantageous for foaming TPU by enabling large reductions in bulk densities without the harmful effects of chemical residue. This novel process of using co-blowing agents yielded the lowest bulk density while achieving the highest cell density and finest average cell size. To resolve the issue of low melt strength at higher temperatures, which leads to cell coalescence and undesirable microstructures, the use of a physical cross-linking agent was considered. It was proposed that a physical cross-linking agent could increase the melt strength of the TPU at higher temperatures, thus enabling aggressive foaming strategies to give enhanced density reductions. It is shown here that extremely low-density TPU foams of bulk density 0.16 g/cm3 (160 kg/m3) can be achieved consistently. In Chapter 3, nanoclay as a reinforcing filler was employed to increase the melt viscosity and to trigger heterogeneous nucleation in the TPU matrix, thereby improving the foamability of TPU while achieving a homogenous microstructure with low average cell size and high cell density. It is generally known that TPU's rebound resilience values decrease with decreasing foam density. It was observed that rebound resilience values could increase significantly if a tunable alignment of microcells can be produced within the part, even while reducing bulk densities. Through the action of mold inserts, the expanding microcells will thereby stretch and align with the intercellular TPU walls and individual molecules in the direction of mold opening. With aligned microcells, the softness of the foams improved significantly, while achieving lower hysteresis loss ratios or energy loss (dissipation). In Chapter 5, a core retraction mold capable of increasing cavity volume was designed and manufactured to enable further study of the phenomenon observed in Chapter 4, with better parameter control. Polypropylene (PP) was the material chosen to validate the capabilities of the mold and the applicability of this technology to materials other than TPU. Core retraction was used with the conventional micro¬cellular injection molding (MIM) process to foam thick PP parts with high density reductions of 30% and 55%. The cavity volume was modified by chang¬ing the retraction distance, which resulted in varying den¬sity reductions. The lowest densities were achieved with a core retraction-aided microcellular injection molding (CR-MIM) process, the results of which could not have been achieved by the conventional MIM process alone. It was shown that the CR-MIM process yielded a better microstructure and a higher tensile modulus than the conventional MIM process. Use of core retraction also yielded more consistent densities and tensile properties at different distances from the gate location. It was shown that by using delay times and holding pressures, cell nucleation and cell growth can be delayed to a more suitable time and melt temperature. Mechanical and energy absorption properties of TPU foam can be varied with the density and microstructure of the foam. In Chapter 6, a new process is developed using core retraction and out-of-mold foaming to develop injection molded parts of varying cross-sections with varying mechanical properties. It was shown that, using this process, very low density foams of less than 0.25 g/cm3 can be produced while maintaining uniform and good microstructures. It was also shown that this technology can be effectively used to vary microstructures, densities, and mechanical properties within an injection molded part locally, depending on the application. In summary, the aforementioned approaches have helped to advance the knowledge of manufacturing TPU foams and other regular thermoplastics with customizable microstructures and mechanical properties for various specific applications.
Download or read book Porous Cellular and Microcellular Materials written by Vipin Kumar and published by . This book was released on 1998 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains the 15 papers presented at the November 1998 symposium sponsored by the materials division of the ASME. The papers are nearly equally divided between the two broad areas of structure-to- property characterization and foam processing. The topics addressed include acoustic, tensile, impact, fracture, and creep behavior of foams. The issues addressed in processing include measurement of gas solubility, approaches to foaming PET, extrusion of microcellular foams and polyethylene foams, and evaluation of blowing agent performance. Two papers discuss the emerging role of porous polymers in biomaterials research. No subject index. Annotation copyrighted by Book News, Inc., Portland, OR
Download or read book Blowing Agents and Foaming Processes 2001 written by and published by iSmithers Rapra Publishing. This book was released on 2001-12-31 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:
