A stiff beam, mounted on the load frame, that is driven up or down using electromechanical force. The force required to drive the crosshead is transferred to the specimen through the grips. Crosshead applies to electromechanical systems only.

The extent to which rubber is permanently deformed by a prolonged compressive load (ASTM D-395). Should not be confused with low temperature compression set.

CEAST stands for Compagnia Europea Apparecchi Scientifici, Torino.  This is an Italian phrase meaning a European Scientific Instruments Company located in Torino.

From the acronym, you may have guessed that CEAST was founded in Italy.  However, today it is no longer just a European company. CEAST was acquired by Illinois Tool Works (ITW) in 2008 and has been positioned under its Test & Measurement Group’s Instron Division.

Today the CEAST product lines are sold around the world through Instron's sales & service team as well as a local agencies.

The company was originally founded in 1953 by Dr. Mario Grosso. CEAST supplied instruments for the Italian Petrochemical Industry that had been destroyed by the World War II. CEAST starting then to develop instruments for polymers characterization, research and quality control, collaborating with Dr. Giulio Natta (Nobel Prize winner for the first synthesis of Polypropylene). CEAST was known for supplying advanced testing equipment for mechanical, physical and rheological characterization of all polymer types with the first Melt Flow instrument in 1960.

Today, CEAST products are still designed and manufactured in Italy.

A capillary rheometer is an apparatus designed to measure shear viscosity and other rheological (= flow) properties. Capillary rheometers for plastics are piston-die systems designed to measure viscosity of polymer melts as a function of temperature and rate of deformation. They are capable of testing basic polymers, compounds, various composites with small reinforcing particles or fibers, feedstock for metal injection molding and similar materials.

The basic principle is that a thermoplastic sample (originally in the shape of granules, powder or flakes) is made fluid by heating and forced to flow out of a cylinder through a capillary die. The measured quantity is normally the generated pressure under steady state conditions. A flow curve is the typical output, obtained by interpolation of several experimental data. Viscosity is represented as the Greek letter “eta” (η) and expressed (in SI units) in pascal seconds (Pa·s) or newton seconds per square meter (N·s/m2).

Capillary rheometers ensure testing conditions which are truly representative of processing conditions, especially for high-pressure and high-speed techniques like injection molding, therefore they are key for process optimization.

Other rheological properties that can be measured or estimated from capillary rheometers data include extensional viscosity, extrudate swell, thermal stability, wall slip. Ancillary measurements can be carried out for thermal conductivity, density dependence on pressure and temperature (pvT), melt strength.

References

• Walters K. “Rheometry”, Chapman & Hall (1975)
• Ferry, J. D. “Viscoelastic Properties of Polymers”, John Wiley & Sons (1980)
• Dealy, J.M. and Wissbrun K.F. “Melt Rheology and its Role in Plastics Processing”, Van Nostrand Reinhold (1990), Chapman & Hall (1995)
• Macosko C.W. “Rheology – Principles, Measurements, and Applications”, Wiley-VCH (1994)
• Malkin A.Y. “Rheology – Concepts, Methods, & Applications”, ChemTec Publishing (2006)

Calibration is the process of comparing an unknown value to a known value. To calibrate a device is to compare a characteristic of that device with the characteristic of a similar device called a “standard.” Using load cells as an example, the load cell being calibrated and the standard load cell are mounted together in series and a range of loads is applied. Both load cells experience the same load and therefore the output values should ideally be identical. A calibration result most often indicates a difference between the two values.

A common misconception is that calibration means adjusting the output of a device to bring its performance “within limits.” Any adjustment made to the output of the device is separate from the calibration and verification process, and must be followed by a further calibration and verification to prove the adjustment was successful.

NOTE: It is important not to confuse CALIBRATION with the term "calibrate" that is sometimes used on instruments to refer to the actions of setting up a transducer such as a loadcell or extensometer to work with the system.

Below are the definitions as defined by the International Vocabulary of Metrology.

2.39 (6.11) calibration
Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, uses this information to establish a relation for obtaining a measurement result from an indication

NOTE 1: A calibration may be expressed by a statement, calibration function, calibration diagram, calibration curve, or calibration table. In some cases, it may consist of an additive or multiplicative correction of the indication with associated measurement uncertainty.

NOTE 2: Calibration should not be confused with adjustment of a measuring system, often mistakenly called "self-calibration," nor with verification of calibration.