Rheometers: How and What do they Measure?

Rheometers: How and What do they Measure?

To measure the rheological properties of your sample with a rotational and oscillatory rheometer requires the determination of the torque and deflection angle of the measuring bob. Your sample provides resistance or a reset torque to the setting. The resulting deflection angle is then measured by the rheometer encoder. The speed is calculated from the deflection angle and the time.


However, as the user, you are usually more interested in the rheological parameters. How do you get these? Rheological parameters are calculated from the measured values torque, deflection angle, and speed using conversion factors. All further parameters, such as viscosity, are not measured but calculated.


There is a new grading system for color concentrates and additive masterbatches. It is the European test of melt dispersability known as FPV or Filter Pressure Value. It is reportedly more stringent than the ASTM dispersion test and a more objective indicator of both dispersion quality in a concentrate and how well it will disperse in a polymer matrix. Above all, it is a single number that shows how a concentrate compares with other products.


What is an FPV?


The basic principle is that you run compounded material through a screen mesh, which gradually blocks up with trapped particles. The time it takes to block and the degree of pressure build-up are a good indication of how well dispersed the masterbatch was. The filter pressure value tester calls for feeding the lab extruder for a period of time only the matrix polymer without masterbatch to get a baseline die-pressure reading. Then you introduce the masterbatch and record how pressure builds as undispersed pigment or other additive is trapped on the screen pack. The test is a combination of time and pressure peak. After a set time, you reintroduce virgin material into the extruder, and the pressure plot starts to drop to show that you are ending the test.


The basic steps of compounding can perfectly be realized with a corotating lab compounding extruder. This makes modular co-rotating twin screw extruders the ideal companion for plastics from synthesis up to recycling. Profit from the harmonized, modular conception of screws and barrels for optimally realizing all processing steps (feeding, conveying, plasticizing, dispersing, reacting, venting, pressure build-up). The system configuration of each model can easily be adapted to the individual processing task - anytime and at a low cost. Or combine several processing steps within a continuously working extruder and use your twin screw extruder as a modern in-line compounder. Depending on the extruder size, on the material to be tested, and on the processing task, throughputs up to 60 kg/h can be reached. This opens up the entire application range to these extruders - from material development up to small-scale production of sheets and films.


Detailed operating procedures of the lab cast film machine:


1. Prepare related tools, such as copper sheet, alcohol, mold release agent, etc.


2. Check whether the die head, rollers, etc. of the casting machine and their surroundings are clean, then clean the die head with alcohol, paraffin wax and gauze, or clean it with a copper sheet and spray it with a release agent.


3. Check whether the rotation and pressure of each roller of the cast film machines are normal and whether the heat exchange system, pump and pressure gauges can work normally.


4. Wear each roller with a thick film through film, and then put the chilled roller in a closed state to press the film.


5. Start the cast film machine, check whether the thick sheet and the melt have adhered firmly and smoothly, and then pull the thick sheet tightly toward the person standing at the exit.


6. Adjust the appropriate working position and carefully complete all operations.


7. After the production is over, manually adjust the cast film machine to the non-working position, and then introduce the material into the receiving tray, and stop the machine.


With the rapid development of industrial science and technology, the lab blown film machine has also mastered the skilled manufacturing process, but compared with the advanced technology level, there are still gaps in some aspects. If the film blowing machine is to achieve rapid development, then it must absorb the advanced technology level, let the film blowing machine develop in a new direction.


The calenders employ two or more steel rolls that close under pressure to smooth, compress, and in some cases partially bond a nonwoven, plastic, paper, or another substrate. The rollers may be mirror-smooth, embossed with a pattern, or porous, and are usually heated with hot oil or electric elements. The lab calender machines can be utilized in an independent converting setting or an integrated production facility.