polymer processing

Once more, technical issue, from Massachusetts Institute of Technology web page click right on Rheological Behavior of Fluids than save target as on your drive, and run using Realplayer Conclusion and complement for part 1/2 , polymer viscoelasticity effects: Weissenberg and Barus . Weissenberg effect during shear flow between two coaxial cylinders appear climbing up along the rotating rod for no-newtonian fluids , that is melted polymers . The same effect can be observe during stain an paint mixing and can not be observe for newtonian fluids , e.g. water. Weissenberg effect is a result in generating during shear flow extra stain, called normal stresses . Barus effect appears during extrusion and it is observed by swelling extruded material leaving nozzle. For melted polymers the effect is big and describe as relation between flow and nozzle diameter, it is beetwen 1,2 - 2,5 . Depends on flow capacity, tool geometry, but the most on relation channel length/diameter and pol...

There will be screenshots from Rheological Behavior of Fluids movie applied, it is available from Massachusetts Institute of Technology web page, Realplayer is an requirement. The movie is s great introduction for no-newtonian fluids (as polymers are) properties. There are many experiments which will be key for polymer processing understanding where this properties emerge. The movie history reaches latest 60th (fundaments for fluid mechanics and rheology are the same) it is not short more than 22 minutes but it is worth seeing more than once. As you listen carefully you will find answers for problems from: newtonian fluids , no-newtonian fluids (Bingham, pseudoplastic, dilatant fluids), viscoelasticity effects , Weissenberg effect , Barus effect , time dependent effects Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Viscous materials , resist shear flow and stain linearly with time whe...