New measuring technique, now commercially available, delivers test series with reproducible and documented results
Extensional flows are latently apparent in many industrial processes and applications, but were not easily measurable up to now.
Materials which behave the same or similarly under shear flow often behave completely differently when subjected to extensional flow.
Thermo Electron has now made it possible for the first time to measure the extensional characteristics of fluids with a commercially available rheometer with the revolutionary new Haake Caber 1.
This means the experimentation phase in this field of research and application technology has now been replaced with the commercial application.
The Haake Caber 1 means the era of experimentation with uncertain results are now over - this unit delivers test series with reproducible and documented results.
It can be used to optimise production processes such as the filling of bottles and beakers (eg for foodstuffs), the portioning of liquid components, the application of adhesives (manufacturing of cardboard), applying coating to paper, spraying paint, the spinning of threads, etc The instrument was developed by the Cambridge Polymer Group and built as a commercially-viable solution by Thermo Electron, Karlsruhe (formally doing business as Thermo Haake).
A drop of the fluid to be measured is placed between two circular plates.
The top plate is rapidly separated from the bottom plate at a user-selected strain rate, thereby forming an unstable fluid filament by imposing an instantaneous level of extensional strain on the fluid sample.
After cessation of stretching, the fluid at the mid-point of the filament undergoes an extensional strain rate defined by the extensional properties of the fluid.
A laser micrometer monitors the midpoint diameter of the gradually thinning fluid filament as a function of time.
The extensional viscosity (together with other variables) is calculated from the raw data.
