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 Professor Avraam I. Isayev Minimize

2012 James L. White Award of Polymer Processing Society for an outstanding innovative development in the field of polymer processing technology

Dr. Avraam I. Isayev, Distinguished Professor of Polymer Engineering at the University of Akron, Akron, Ohio, USA made significant fundamental contributions to polymer processing and their modeling including the injection, co-injection, transfer and compression molding of plastics and rubbers and gas-assisted injection molding of plastics, rheo-optics, rheology and constitutive equations of plastics and elastomers, oil products and disperse systems. He discovered and investigated extensively continuous processes for ultrasonic decrosslinking of rubbers and thermosets, self-reinforced or in-situ composites based on polymer blends involving thermotropic LCPs, continuous processes for in-situ ultrasonic copolymerization of polymer blends with the aid of high power ultrasound and continuous processes for ultrasonic dispersion of various nanofilllers in polymer melts.

Among the numerous problems which mankind face in the 21st century the problem of waste utilization including re-processing and re-using of rubber wastes is enormous. Current rubber recycling technology is mainly based on burning used tires to recover their caloric value which is only about two times higher than the caloric value of coal. Also, tires are crushed into fine particles for addition to virgin rubber as a filler. Dr. Isayev discovered and patented extrusion process and equipment for ultrasonic devulcanization of rubbers and crosslinked polymers. It was shown that ultrasonic waves at certain levels in the presence of heat and pressure within seconds or less are able to break down the three-dimensional structure of the crosslinked rubber. This devulcanized rubber becomes soft, reprocessable and curable. The process does not require the use of any chemicals and allows one to save energy that is needed in making new rubbers. It also creates new materials and products. Dr. Isayev with his colleagues carried out significant experimental and theoretical studies to develop the new science-based technology and provided the scientific understanding of novel devulcanization processes. They proposed the model and mechanism of devulcanization by considering ultrasonic wave propagation in a moving viscoelastic medium providing high local energy density leading to overstressed chemical bonds causing break up of various crosslinks leading to devulcanization and decrosslinking. Ground rubber tire and various rubbers, including natural and synthetic rubbers, were devulcanized. The mechanism of the proces was elucidated. The devulcanized rubbers were revulcanized, and their properties have been studied. The influence of processing conditions on the rubber properties was investigated. Gel fraction and crosslink density of the devulcanized samples, as well as the mechanical properties of the re-vulcanized rubbers were analyzed as a function of processing parameters including amplitude of ultrasound, flow rate, clearance of the treatment zone, temperature, pressure, and ultrasonic power. The crosslink density of the various devulcanized rubbers was found to correlate uniquely with their gel fraction and independent of parameters characterizing the energy absorbed. Hence, the degree of devulcanization can be characterized by just one parameter, such as the crosslink density or gel fraction of the devulcanized rubber. The most comprehensive parameter characterizing the extent of the treatment is found to be the specific acoustic energy consumed per unit mass of the rubber which according estimates adds only one cent into cost of rubber. The industrial application of this technology will have a significant impact on the further expansion of the recycling technology in automotive, shoe, building and tire industries. The technology was licensed by the University of Akron to Avraam Corp., which is a rubber recycling company. The first industrial devulcanization extruder with 3.5 inch screw was built, tested and sold. The design and manufacture of the novel industrial devulcanization extruder was funded by NIKE which has business around the globe. Several companies participated in the design and manufacturing process, including Branson Ultrasonics, FM Machine and Davis Standard. The technology is economically feasible because the cost of devulcanized rubber is significantly lower than that of new raw materials. Factory rubber waste will be eliminated by incorporation of devulcanized rubber into manufacturing stream. Therefore, this novel process will have a significant impact on the economy when applied regionally, nationally and globally. This technology has been awarded two US patents and many international patents. Recently, a new US patent and PCT patent application was filed for decrosslinking of crosslinked plastics and rubbers using ultrasonic twin screw extruder which is even more efficient than earlier techniques.

Dr. Isayev with his colleagues discovered and patented the novel process for manufacturing of self-reinforced or in-situ composites based on thermotropic liquid crystalline polymer (LCP)/thermoplastic and LCP/LCP blends and initiated significant experimental studies in this area. He showed that at certain processing conditions and LCP concentrations, LCP has the ability to form microfibrils or fibers in diameters from 0.1 to 10 micrometers in the thermoplastic matrices during the processing step. The novel process provides self-reinforced composites that exhibit high mechanical strength, excellent thermal and chemical resistance along with ease of processing. Through his research over 25 years the science based technology of self-reinforced composites was developed to identify processing conditions for successful fibrillations of various LCPs in thermoplastic matrices. In addition, he proposed a patented technology for preparation of laminates of self-reinforced composites based on interplay of melting points of components in blends. Furthermore, self-reinforced LCP/LCP blends were manufactured by injection molding process with performance properties of moldings significantly higher than those of any currently existing thermoplastics. This research culminated in twelve US Patents and many international patents.

Dr. Isayev with his colleagues discovered and patented and carried out fundamental studies on high power ultrasonic-assisted extrusion process for in situ copolymer formation and compatibilization of blends of immiscible polymers in the melt state. The process takes place at a very short time (about 10 s) and leads to a stable blend morphology in the melt state and significantly enhancemes the mechanical properties of the in-situ compatibilized blends. The enhancement of reactions of transesterification in blends was also obtained.

Dr. Isayev and his colleagues published fundamental scientific articles related to development of basic experimental and theoretical understandings of molding processes especially related viscoelastic effects. Specifically, they published experimental and theoretical articles on the frozen-in molecular orientation and residual stresses in injection moldings of amorphous and semicrystalline polymers and developed methodology to include the effect of the flow-induced crystallization and quescient crystallization on structure development in moldings of semicrystalline polymers. Based on these developments, they proposed a new theoretical approach to simulate anisotropic shrinkage in moldings. The predictions were extensively verified against an extensive experimental data. For amorphous polymers, the approach was based on use a compressible nonlinear viscoelastic constitutive equation to calculate the residual flow stress tensor components and to relate them to various components of birefringence through use of the stress-optical rule. Contribution of the thermal stresses to birefringence was calculated based on the photoviscoelastic constitutive equation with measured the stress- and strain-optical behavior. In semicrystalline polymers, in addition to the above effects, the flow-induced crystallization was included. Recently, they carried out pioneering fundamental studies on injection molding of light guide plates (LGPs) with surface microstructures and found a strong correlation between their luminance and degree of filling of microstructures and frozen-in birefringence in LGPs.

Dr. Isayev and his colleagues made pioneering contributions to development of the science-based technology for injection molding of rubber compounds and carried out extensive experimental studies to verify the proposed approach. Based on this achievement it is now possible to specify the suitable processing conditions in rubber injection molding to avoid premature curing during cavity filling and to determine the state of cure distribution in molded products. Isayev developed the methodology to characterize curing kinetics required for successful injection molding of rubbers including incorporation of nonisothermal cavity filling combined with nonisothermal induction time and nonisothermal cure kinetics. This development is currently utilized in moldflow software for rubber injection molding.

Dr. Isayev and his co-workers carried out the first successful viscoelastic and viscoelastic plastic simulations of two-dimensional planar contraction and expansion flow at Deborah numbers as high as 1000 corresponding to melt flow in polymer processing. This was the long standing problem. Many attempts were made in literature by various research groups, but they were unable to get solution above Deborah number of the order of one. Isayev’s group was able to overcome this limitation and compared theoretical predictions with experimental data on build up and relaxation of birefringence in converging and diverging flows at high Deborah numbers. Later, his group extended the developed approach to solve the problem of viscoelastic flow in channels with moving boundary, such as occurs in non-return valves of injection molding machines. Furthermore, his group did pioneering experimental and theoretical studies on dynamic behavior of various non-return valves and provided their ranking with respect to their ability to close during injection of different thermoplastics which provided basis for choosing suitable non-return valves in injection molding machines.

Dr. Isayev and his co-workers developed novel methods for continuous dispersion of nanofillers in polymer matrices for manufacturing nanocomposites using ultrasonically assisted single and twin screw extrusion processes. They carried out fundamental studies on mixing of carbon nanotubes, carbon nanofibers and various particulate nanofillers in thermoplastics and rubber matrices. They found significant changes in percolation threshold and thermal and electrical conductivities under action of ultrasound in extruders.

Dr. Isayev with his research team published 230 papers in referred journals, 30 chapters in books, 7 articles in encyclopedias, 151 papers in conference proceedings and presented 275 papers at the national and international conferences, including plenary, keynote, invited and contributed lectures and 114 seminars over the world. He holds 25 patents and many international patents. He taught a number of short courses in US and around the world. He co-authored 1 monograph, edited or co-edited 7 books. He graduated 40 PhD, 36 MS students and advised 28 postdocs and visiting scientists. He is the Editor-in-Chief of the Advances in Polymer Technology and served on 11 editorial and advisory boards of various journals. His work was featured in PBS TV, Science Update of AAAS, numerous newspapers and trade journals around the world. He is a partner and Chief Technology Officer in Avraam Corp, A Rubber Recycling Company, Akron, Ohio.

Dr. Isayev is the recipient of number of honors and awards, including the Young Scientist Award (Moscow), OMNOVA Solutions Signature University Award from the OMNOVA Solutions Foundation, the Melvin Mooney Distinguished Technology Award and Stafford Whitby Award for Distinguished Teaching and Research from Rubber Division of the American Chemical Society, the Silver Medal from the Institute of Materials (London), the Vinogradov Prize from the G. V. Vinogradov Society of Rheology (Moscow) and NorTech Award. His biography is listed in many Who’s Who Publications. He is the Fellow of the Society of Plastics Engineers.

Prior to joining the University in 1983, Dr. Isayev conducted research at Cornell University, Technion, Topchiev Institute of Petrochemical Synthesis of the USSR Academy of Sciences, and the State Research Institute of Nitrogenic Industry, USSR.


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