A rotational rheometer is a physical analysis instrument used to study the rheological properties of materials. It measures parameters such as shear rate and stress of materials by applying different loads, and then calculates rheological parameters such as viscosity and storage modulus to characterize the flow and deformation characteristics of materials.
The rotational rheometer applies external forces to materials by controlling stress or strain, observes the response of materials to loads, mainly measures data such as shear rate, shear stress, oscillation frequency, etc., and then calculates parameters such as viscosity, storage modulus, and loss modulus.
The rotational rheometer drives the measuring fixture (such as cone plate, parallel plate, or coaxial cylinder) to rotate through a driving system (such as a cup motor or air bearing), applying shear force to the sample. When the sample undergoes shear deformation, the sensor monitors the shear stress and shear rate in real time and transmits the data to the control system for analysis. According to the different rheological behaviors of materials:
Newtonian fluid: Shear stress is proportional to shear rate, and the proportionality constant is viscosity.
Non Newtonian fluids: viscosity varies with shear rate, exhibiting complex characteristics such as shear thinning, thixotropy, or yield stress.
measurement type
Steady state measurement: Apply a constant rate or stress to measure the viscosity, flow curve, etc. of the material.
Dynamic measurement: Apply sine periodic strain or stress to analyze the elasticity (storage modulus) and viscosity (loss modulus) of materials.
Precautions for use:
Sample preparation: Ensure sample uniformity, avoid bubbles, and perform defoaming treatment if necessary.
Temperature control: Strictly stabilize the sample temperature and reduce the impact of thermal expansion on the test results.
Fixture selection: Choose a suitable fixture based on the viscosity of the sample (such as using a cone plate for high viscosity samples and a parallel plate for low viscosity samples).
Data validation: Take the average of multiple measurements and compare it with a standard sample to ensure the reliability of the results.