Capillary rheometerTechnology is mainly divided into two categories: constant velocity capillary rheometer and constant pressure capillary rheometer. In addition, from the perspective of measurement principles, gravity capillary rheometer (such as Ubbelohde viscometer) can also be mentioned. The following is a detailed introduction to these two types of technologies:

Constant speed typeCapillary rheometer

Working principle: Maintain a constant downward pressure velocity of the plunger and measure the pressure difference between the two ends of the capillary tube.

Features:

The material flow rate can be obtained from the forward speed of the plunger.

The pressure can be measured by the load unit on the plunger (such as an Instron rheometer) or the pressure sensor on the barrel wall (such as a Gottfert rheometer).

Wide measurement range.

Suitable for studying the effect of shear rate on viscosity, with simple operation and accurate measurement.

Application:

Measure the relationship between shear stress and shear rate of polymer melt in capillary tubes.

Study the elasticity of melt and unstable flow phenomena such as melt fracture.

Predicting the processing behavior of polymers provides a basis for selecting composite formulations, seeking optimal molding process conditions, and controlling product quality.

Provide basic data for the auxiliary design of polymer processing machinery and molding molds.

As an auxiliary tool for characterizing and studying the structure of polymer macromolecules.

Constant pressure capillary rheometer

Working principle: Maintain a constant forward pressure of the plunger and measure the extrusion flow rate (speed) of the material.

Features:

Suitable for simulating constant pressure conditions in actual machining processes.

Evaluate the flowability of materials by measuring extrusion speed.

Application:

In the plastic industry, the commonly used melt index measuring instrument is a constant pressure capillary rheometer.

Used to evaluate the extrusion behavior of materials under constant pressure, such as injection molding, hot melt extrusion molding, etc.