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Rheometer for solids testing
Rheometer for solids testingKeywords: Bohlin Instruments, Rheology
The new CV01 20 Rheometer from Bohlin Instruments is said to be able to measure the mechanical properties of solids and films across a broad temperature range.
Bohlin informs us that the rheometer incorporates a purpose built DMTA cell, allowing full-length solids and delicate films to be easily mounted in specially designed test clamps. The company also reports that its Windows software enables temperature gradients to be pre-programmed over the range -150°C to +550°C and generates parameters such as the glass transition temperature and the complex modulus. The cell is said to be extremely easy to use, minimises temperature gradients through the sample and the ultra low compliance test fixtures ensure that the correct value of the modulus is always measured.
To ensure that quality and reliable data can be produced at modulus extremes, all measurements are made using autotension. In this mode a constant tension is applied along the sample which is said to ensure that it never buckles or fractures. The tension is regulated through a normal load sensor with a resolution of better than 0.1 grams.
Advanced data analysis software enables construction of master curves using time temperature superposition and calculation of retardation and relaxation time spectra.
For measurement of polymer melts and thermosets the DMTA cell is supplied with a range of conelplate and parallel plate measuring geometries. Mechanical spectrum measurements and creep compliance testing produces data to enable interpretation of average molecular weight and molecular weight distribution.
Bohlin Instruments also announces new software that in its opinion combines flexibility with the facility of advanced programming, thus enabling the performance of a broad spectrum of rheological tests. The software is reported to neatly combine an accessible user interface for complex method set-up along with real time data processing to encompass the needs of industrial and academic users alike.
The software is described as featuring operating routines such as viscometry, creep compliance, oscillation and a direct link to a context sensitive help system giving users immediate advice on applications and basic principles. The data analysis is integrated within each mode and there is a comprehensive choice of rheological and mathematical models allowing data to be rapidly quantified, thus avoiding the need to use external modules.
The software is thought to benefit from a number of new features that extend the measuring range. For solids testing the autotension dialogue provides normal force control during a temperature gradient enabling the glassy region to be clearly defined and transitions reproducibly measured. The curing mode has provided additional measurement capabilities for thermosets, resins and gels combining excellent strain control with accurate modulus determination.
Low viscosity fluids testing has reportedly been enhanced using active inertia control and for non-linear viscoelastic systems the First Normal Stress and Shear Viscosity are plotted simultaneously. One of the most significant features claimed is perhaps the software's interactive gap control system that enables the measured gap to be captured remotely at the rheometer sample stage and automatically downloaded to the operating method.
The NT software is stated to be compatible with the complete range of Bohlin rheometers CVO, CS, CVR, CSR, V88, DRS, and ADS. Upgrade licences are now available as well as demonstration versions on CD.