What is the meaning of Rheology?

If you pour water in a glass, you are already active in the field of rheology.
Rheology deals with the flow behavior of materials. How is the flow behavior of the materials?
What will happen if you apply pressure on the material or the temperature is changed?

Such and other questions are clarified at Goettfert site. But instead of testing water we test polymers, plastics and rubber materials.

Viscosity

Viscosity means the flow characteristics of a material. The slower the material is flowing, the more viscous the material is and the higher is the viscosity.

Materials can change its physical state (solid, liquid, gaseous) under influence of increasing temperature, consequently higher temperatures may also change the flow characteristics.

Example

From home everybody knows the phenomenon with the nougat crème in the fridge. The mixture is solid and you cannot just simply spread it on the bread as it is very though and its viscosity is high.

Leave the glass at room temperature for several hours, the nougat crème gets soft and you can spread it easily. Its condition is not liquid and not viscous.

However, you are in a hurry and place the glass in the microwave, the nougat crème warms up and gets liquid. Due to its low viscosity the crème gets fluid and it is impossible to spread it on the bread without producing a big mess… 😁😋

Rheologie NussNougat

.......................................................................................................................................................

Our new automatic Melt Indexer MI-ROBO

NOW with integrated Die Cleaning

 

The MI-ROBO 89.16 is presented at the K 2016 with some new features. By its high automation the Automatic Melt Indexer contributes to an even increased accuracy. The reason for this high accuracy is the “operator factor” usually being an important issue, but here it is completely omitted during the fully automated melt flow tests of the MI-ROBO contrary to manual and semi-manual operated MI devices. The melt flow tests are according to the standards ISO 1133 and ASTM D1238.

One innovation is the force-controlled pre-loading function and the force-controlled ejection function at the end of the measurement by drive and test weights (up to 60kg).

The force-controlled pre-loading function is for more precise test procedure and test results.

The force-controlled ejection function for ejecting the test material at the end of the measurement contribute to a high user convenience. The new MI-ROBO 89.16 is now equipped with an integrated die cleaning function. The die cleaning is automatically performed by the system and the die is directly available for subsequent tests.

New features of the MI-ROBO are the optimized replacement of the cleaning roll and the use of electric motors instead of pneumatic motors. As a result, both, noise level and air consumption were reduced significantly.

To complete the mentioned features we like to emphasize the accelerated weight selection and the optimized piston cleaning to provide fast availability of the weights and the test piston for subsequent test. It is also possible to connect the MI-ROBO 89.16 to an Online-Sampler for feeding test material directly from the production line.

 

 mi-robo 600px

 

 

 
.......................................................................................................................................................

PVT

PVT Measurement isothermal/isobaric air-cooled up to 500 °C

 

The new test device PVT is specifically designed for measurements of PVT isothermal and PVT isobaric.

With this device thermodynamic properties, the specific volume of the polymer as a function of temperature and pressure, can be determined. These data are particularly important for the simulation of the injection moulding process. But they also can be used to describe any process of shrinkage during cooling as for example in extrusion.

 

The measurement can be performed in two possibilities:

ISOTHERMAL – at constant temperature and changing pressure or

ISOBARIC – at constant pressure with different cooling rates.

 

The device is characterized by its compact test chamber and by its new optimized cooling system. The cooling medium is air, therefore no cooling water connection is required.

As an option also the thermal conductivity of the material can be measured.

 

 pvt 600px

 

 

 
.......................................................................................................................................................

Spin Line Rheometer (SLR)

Extensional Rheometer for high Haul-off Speeds

 

Melt spinning is an important production process for chemical fibers made of synthetic or biologically based polymers. The new Spin Line Rheometer introduced by GÖTTFERT is a measurement system to characterize the spinnability of polymers in lab scale. The system can be installed under an extruder or a capillary rheometer and is able to measure the strand force and therefore the extensional viscosity at spinning speeds of up to 7000 m/min.

 

The strand is guided around the diversion-wheel that is placed horizontally below the extruder die. The wheel is installed on a highly sensitive force sensor with a resolution of 0,05mN that measures the draw-down force in the strand. The strand is accelerated by the take-off wheel installed on a high-speed electric motor. A strand guide makes multiple wrappings possible. A Venturi-Die is used to separate the strand from the take-off wheel. Optionally an optical measurement system can be installed to measure the strand profile at various positions between the die and the diversion-wheel. A new, extended version of the Rheotens-Software is used to control the measurement system and to analyze the data.

 

 spin 600px

 

 

 
.......................................................................................................................................................

CONTIFEED

Our fully automated Melt Feeding Unit

 

The CONTIFEED offers new possibilities for determination of process-related rheological test data. The system is combined of a capillary rheometer Rheograph 50 and a Mini-Extruder. The Extruder feeds the test barrel of the Rheograph with melt, which ensures an air bubble free filling of the test barrel. This continuous method of melt feeding contributes to a significant timesaving during the tests. The reduced material residence time under influence of elevated temperatures is just one of the advantages due to shortened heating time by optimized and effective heating system.

 

As a result of this short heating time the CONTIFEED is specially suitable for elastomers and thermally less stable material. By pre-plastification also powder materials, e.g. PVC dry blends can be measured.

 

 conti_gr 600px

 

Figure: Reducing the material residence time after the homogenization of the pressure course by the pre-plastification of the melt feeding extruder (20mm/10D).

 

 conti 600px

 

CONTIFEED

 

 conti_2 600px

 

Scheme: continuous Melt feeding

 
.......................................................................................................................................................

GOETTFERTtv

Visit our Youtube-channel