RHEOGRAPH Add-On

The RHEOGRAPH from GÖTTFERT is a modular platform for the advanced characterization of polymers. The capillary rheometer serves as the basic instrument to which various additional add-ons can be added. The RHEOGRAPH can thus be optimally adapted to the individual requirements of each application. With the fully equipped version, the processing behavior can be characterized completely.

The basic instrument of GÖTTFERT capillary rheometers is designed to carry out viscosity measurements with plastics, rubbers and a variety of other materials.

By using modular Add-Ons additional characterization possibilities can be used.

The SHARK-SKIN measuring head is mounted at the bottom of the test barrel instead of the capillary. With this option it is possible to measure exactly at which critical shear rates surface inhomogeneities occur.

  • Detection of the SHARK-SKIN effect
  • Consisting of slit die, three high frequency pressure-sensors (sampling rate up to 20 kHZ), as well as software package
  • Determination of the frequency spectrum and statistical evaluation of the pressure signal
  • Optimization in the extrusion, film and coating process

 

The sensor for thermal conductivity is mounted just like a standard piston. The barrel is closed at the bottom during the test. The thermal conductivity measurement of solids or melt is performed under stationary conditions.

  • Determination of the thermal conductivity at a measuring range up to 450°C and 1000 bar
  • Developed according to ASTM D5930
  • Test sensor with integrated heating element and temperature sensor
  • Process-Simulation and optimization of cycle times in injection molding
  • No mechanical modifications necessary
  • Fully automatic measurement

 

The CONTIFEED is a mini-extruder which directly feeds the test barrel of a capillary rheometer. This add-on is particularly suitable for thermally unstable material, due to the reduced dwell time. The plasticizing with pre-shearing in the extruder, makes the measuring process very similar to the production process.

The advantages of the CONTIFEED:

  • Automated, bubble-free filling of the test barrel
  • Influence of plasticizing via extruder can be investigated
  • Shorter material dwell time under temperature influence
  • Rheological characterization at conditions similar to the production process
  • Pre-plastification also allows the measurement of powder materials (e.g. PVC dry blends)

 

Besides the PVT 500, GÖTTFERT also offers the PVT-measurement as an add-on for the capillary rheometer. The measurement characterizes the material specific dependencies between pressure, specific volume and temperature.

  • Isothermal or isobaric measurements according to ISO 17744
  • Constant high cooling rate with newly developed air cooling or thermostat
  • Fully automated measurement
  • Automatically generated PVT diagram
  • Parameterization with Tait model as interface to simulation software

 

Principle of pVT measurement (isothermal)
Principle of pVT measurement (isobaric)

The drawability of polymer melts is of utmost importance in many processes of plastics production and processing.

The patented RHEOTENS method has proven to be an extremely sensitive measuring principle that delivers highly reproducible results to show even minimal batch fluctuations.

In addition to the already existing constant speed and constant acceleration, exponential acceleration is now also possible. The determination of the extensional viscosity function according to Prof. Wagner is an integral part of the RHEOTHENS.

The RHEOTENS is well suited as a processability test for materials used in extrusion or film applications.

 

Our newly developed HAUL-OFF with a maximum speed of 2000 m/min is particularly suited for the characterization of fibre-grade materials. The system can be operated with constant acceleration or at constant speed steps. The pull-down force is measured via a smooth-running, anti-stick coated measuring wheel on a highly sensitive force transducer.

 

 

 

The measuring head is mounted below the die. The measurement can be carried out parallel to a viscosity measurement.

  • Determination of the dynamic and static die swell
  • Evaluation of a die swell profile (BASELL method)
  • Swivel arm with continuous height adjustment
  • Laser measuring head in 0.1 μm or 7 μm version
  • Optional with automatic melt cutting device
  • Optional: acquisition of two strings simultaneously
  • Application: Simulation of material swelling behaviour during extrusion

 

The viscosity of polymers can also depend on the general pressure level. The Counter Pressure Chamber is mounted behind the die and generates a back-pressure at the die outlet, which is measured with an additional pressure sensor.

  • Determining the pressure dependence of viscosity (pressure coefficient)
  • Determination of the critical wall shear stress for wall slip
  • Maximum pressure (Pm) 1200 bar
  • Temperature range up to 400°C
  • Optimization of the flow processes in processing machines (injection molding and extrusion tools with long flow paths, melt pumps)

 

Applications

PVT isobaric

This procedure is standardized in ISO 17744 for piston operated instruments. Isobaric PVT measurements are performed at constant pressure...

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PVT isothermal

In isothermal PVT measurement, the measurement process starts at room temperature after the material is filled at melt temperature and...

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Bagley Correction

The Bagley correction is needed to calculate the inlet pressure drop when round hole capillaries...

 

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Weißenberg-Rabinowitsch Correction

Due to shear thinning of polymer melts with pseudoplastic flow behaviour a strong flection of the...

 

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Thermo Stability

Plastics have the property of aging through thermal or mechanical stress...

 

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Melt Elasticity/Strength

The melt strength (elasticity) is determined by withdrawing an extruded strand of capillary rheometer...

 

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Counterpressure chamber

The counter pressure chamber, which offered by GÖTTFERT as an optional Add-on ...

 

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Flow Instabilities (Shark-Skin)

The Shark-Skin effect occurs during the extrusion of plastics, elastomers or food and manifests...

 

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Thermal Conductivity

The measurement of the thermal conductivity is carried out by means of a probe...

 

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Extensional viscosity (Cogswell Modell)

The extensional viscosity can be calculated with measured data of a capillary rheometer...

 

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Die Swell Measurement

The Die Swell measurement is one of many available add-ons for the series of GOETTFERT capillary rheometers...

 

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