Soon after arriving at McMaster University in 1968, John Vlachopoulos focused the research efforts of his teams of graduate students, research staff and postdoctoral fellows on polymer processing and rheology. The Centre for Advanced Polymer Processing and Design (CAPPA-D) was formed in 1987. His...
Soon after arriving at McMaster University in 1968, John Vlachopoulos focused the research efforts of his teams of graduate students, research staff and postdoctoral fellows on polymer processing and rheology. The Centre for Advanced Polymer Processing and Design (CAPPA-D) was formed in 1987. His former students and coworkers that worked on the various projects are now university professors or occupy important positions in industry in Canada, USA, South America, Europe and Far East. Special emphasis was placed on developing mathematical models and solving problems of industrial relevance and importance, using finite element and finite difference methods. The most important research accomplishments and projects include:
1. EXTRUDATE SWELL and MELT FRACTURE: Relations involving molecular weight distribution and elucidation of the role of molecular disentanglements.
2. CALENDERING. Models with and without the hydrodynamic lubrication approximation involving wall slip and normal stress effects. Prediction of forces, pressures, torques and the existence of vortices in the melt bank.
3. PLASTICATING and REACTIVE EXTRUSION: Models of the entire plasticating single screw extrusion process from hopper to die exit and applications to screw design as well as in simulation of peroxide degradation for the production of controlled rheology PP.
4. DIE EXTRUSION and COEXTRUSION: Simulation of flow through dies for the production of cast film, sheet, blown film, profiles and development of computer assisted methodologies for design of flat, spiral and profile dies using 2-D models of non-Newtonian polymer flow. Study of special problems in multilayer extrusion using 3-D simulations.
5. FOUNTAIN FLOW IN INJECTION MOLDING: First ever published simulation of this phenomenon as well as elucidation of the role of kinematics, shear thinning and viscoelasticity, explanation of the origin of V-shapes and other effects during the cavity filling process.
6. THERMOFORMING: Finite element simulation of polymer sheet inflation involving Hyperelastic and Viscoelastic constitutive equations with and without the membrane approximation.
7. PARTICLE COALESCENCE (SINTERING): Frenkel’s 1945 model, which was applicable to the very early stages of the process, was extended for the first time to full completion and inclusion of viscoelasticity. Experimental verification was carried out in specially developed particle sintering apparatus.
8. ROTATIONAL MOLDING: Development of rheological characterization techniques and observations of the sintering process under a microscope for the determination of rotomoldability of resins. This method is now used in industry for screening of polymer resins for the rotational molding process.
9. BLOWN FILM EXTRUSION: Elucidation of interactions between polymer rheology and the aerodynamics of cooling including the Venturi and Coanda effects. Study of external single and dual orifice external cooling jets and internal bubble cooling (IBC).
10. PLASTIC WOOD COMPOSITES EXTRUSION: First ever published studies of the skin and edge tearing phenomenon that appears as some sort of exaggerated sharkskin. Detailed rheological studies of heavily filled polymers and study of wall slip phenomena.
11. RHEOLOGY OF BIODEGRADABLE POLYMERS: Studies of viscoelastic behaviour, extrudate swell and melt flow instabilities of biodegradable polyesters