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Capillary rheometry has been central to his research efforts in the area of polymer rheology and processing. It has been used many times in his lab to mimic polymer extrusion of various polymers and plastic compounds. Capillary rheometry has been used in his research to analyze the slip flow of polymers, the rheology of polymers and plastics at high shear rates, to address the effects of viscous dissipation and high pressure on viscosity as well as to study polymer formability and processability.

Cold extrusion has been used to study the processing of polytetrafluoro polymer and ultra high molecular weight polyethylene in the form of paste. The fundamentals of such processes have been studied in detail and all critical issues associated with this process have been mastered in his research efforts. Preforming, degassing, cold extrusion of pastes, formability, and drying of the final product have been studied in detail.
Polytetrafluoroethylene (PTFE) paste extrusion has been studied in great detail including preforming, flow, extrusion, drying and sintering. PTFE tube extrusion, wire coating have also been particularly studied. Several publication in the open literature have been produced by his group. ExpertHatzikiriakos is perhaps the top world's expert in the area of PTFE paste extrusion.

The rheology and processing of fluoropolymers (several types) has been studied in capillary extrusion in order to identify the critical conditions for the onset of flow instabilities and wall slip. Typical resins studies were copolymers of tetrafluoroethylene(TFE) and hexafluoropropylene(HFP) and TFE/HFP/PAVE (perfluoro(alkyl vinyl ether) (PAVE) respectively. All flow regimes have been identified and studied in detail. Processing aids for the extrusion and processing of fluoropolymers have been identified that reduce dramatically the pressure drop along the capillary die and eliminate instabilities.

Plastic forming has been studied from many different points of view. These include capillary extrusion, single screw extrusion, parison formation and solidification as well as molding. In all these processes many critical issues exist that contribute to plastic forming. Polymers studied include polyethylenes, polypropylenes, fluoropolymers, PET and PVC.

Plastic molding has been studied in his lab for various polymers including polyethylenes, polypropylenes, fluoropolymers, PET and PVC. In rheology the most critical initial aspect is the formation of a suitable sample. Such samples are formed through compression molding. In such processes, temperature and pressure should be carefully selected as well as the cooling process to avoid detrimental effects such as frozen stresses, weld lines, micro-cracks etc.

Polymer extrusion is the basis for many other polymer processes. In his research the polyethylene extrusion has been studied as single-screw extrusion, twin screw extrusion and capillary extrusion. Extrusion of polyethylene blends has also been studied. A critical parameter in the extrusion of polyethylenes is the use of processing aids and in this area his group has perhaps the best expertise in the world.

Polymer processing includes many fundamental processes such as extrusion, fiber spinning, film blowing, blow moulding, co-extrusion and injection moulding. He has recently edited a book on polymer processing and instabilities, control and understanging. He is also teaching courses and short courses on polymer processing in general and therefore he has mastered all fundamnetal issues associated with polymer processing, instabilities and processing aids. In addition he has mastered the importance of using rheological techniques to understand polymer processing.

Polymer Rheology is central to ExpertHatzikiriakos' research. In his efforts rheology is used as a tool to solve practical problems in polymer processing. In general it is difficult to understand polymer and plastic processing without understanding their rheology. Therefore it is crucial to relate polymer rheology with molecular structure and processability. This is the main philosophy to ExpertHatzikiriakos research. In the area of applied polymer rheology is a world's expert and has consulted with many companies including ExxonMobil, DuPont, Daikin Chevron Phillips etc.

DuPont & de Nemours Co., Wilmington, DE, USA (October 1992-2001)
He was developing processing aids that help plastics processors to increase rate of production in various processes Carborundum, Buffalo, NY, NY (September 1998-December 2002)
He was studying the properties of Boron Nitride (a technologically important material) for potential applications to polymer processingChevron Phillips Chemicals (March 2007- current)
A new technology HDPE could not be processed properly. He is studying ways to enhance processingDuPont (1999-2001), Daikin (2001-2004), Solvay Solexis(2004-2006), Donaldson Co (2006-2007), Tensolite (2007)
He studied the issues and difficulties associated with the paste extrusion of PTFE (an extremely important material technologically).RoofRoc. BC, (May 2000-Sept. 2001)
He developed a slate for roofing applications from completely recycled materials. The company now is commercially producing the slate.