Using a commercially available capillary rheometer is convenient because it is a complete measurement device, but it is also possible to use the devices around it to understand the principle of measurement. In this section, we will introduce a shear viscosity measurement device using an injection molding machine that we manufactured. As a separate document, we will also introduce the model numbers of the various dies and devices we have manufactured as measuring instruments. The measurement method will also be introduced separately.
The shear viscosity measurement device using an injection molding machine has several advantages.
(1) Since a normal molding machine is used, the measurement can be made close to the actual situation when kneading is done in the molding machine.
2. The plasticizer/injection device of the injection molding machine can be used to flow even highly viscous resins.
3. By designing the flow path, it is possible to easily measure the shear rate near the desired shear rate.
On the other hand, there are many disadvantages.
On the other hand, there are many disadvantages.
On the other hand, there are many disadvantages: 1) It is not a dedicated machine, so the measurement work and the preparation of the equipment itself are complicated.
2. The equipment is large, so it is necessary to consider the heat generated in the measuring die.
3. It is necessary to devise a way to suppress the variation in temperature and resin flow within the measurement die.
Particularly for disadvantage 3, it is difficult to decide whether to devise a device or a measurement method. At our company, we used a screw preplastic injection molding machine manufactured by Sodick. Since the injection mechanism is a plunger, there is no need to be conscious of the clamping of the backflow prevention valve, and this will reduce the problems of data interpretation during measurement, such as how to consider the difference between the apparent flow rate and the actual flow rate due to the backflow of resin depending on the injection speed.
In the mid-1990s, when this device was first manufactured, there was a lot of interest in measuring shear viscosity at high shear rates because of the possibility of large pressure loss when flowing through narrow areas such as gates. In this system, viscosity measurement was also conducted in the range of several hundred thousand [1/sec] in apparent shear rate (calculated shear rate), but it was confirmed that slippage occurred on the wall, and the measurement range of resin properties itself did not extend that far. In the measurement at low shear rate, when the molten resin after the measurement was discharged fell down, it was observed that the weight of the discharged resin dragged the resin in the measurement die. When measuring shear viscosity at low shear rates, it may be necessary to devise a new device or measurement method. During the measurement, it is necessary to be aware of unstable flow in the measurement system, and to collect data while observing it each time.
The configuration of the apparatus is shown here.
Remove the nozzle of the injection-molding machine and install the adapter and the viscosity measurement die. The purpose of the adapter is to connect the part of the injection-molding machine where the conventional nozzle is screwed into the plasticizer and the viscosity measurement die. It would be acceptable to integrate the two, but as shown earlier, the design of the viscosity measurement die is also related to the measurement, so an adapter is included as one part. The adapter can be screwed in with a pressure sensor (P1) and a temperature sensor (T1); T1 is inserted into the resin flow path and is intended to measure the resin temperature flowing into the viscosity measurement die. P1 is a pressure sensor that requires less precision in the measured values. The P1 is a pressure sensor that requires less precision in the numbers measured. It is basically used as a trigger signal for a device that captures data, and can be substituted with other signals such as the injection start signal if an injection molding machine is used.
The viscosity measurement die has a cylindrical hole and measures the physical properties of the resin flowing through the channel. P2 and P3 are small holes made to create a resin pool and measure the pressure there so that the flow line of the cylindrical channel is as undisturbed as possible. Since T2 and T3 cannot appear in the flow channel, thermocouples are inserted to the very edge of the cylindrical flow channel to indirectly measure the resin temperature.
The viscosity measurement die and adapter must be individually temperature-controlled by band heaters so that the temperature in the flow channel is controlled to be at the measurement temperature.
The data logger (recorder) has an AD converter that can input the output of the pressure sensor as a voltage and the output of the temperature sensor as a thermocouple. Most of the data loggers (recorders) are capable of relatively fast sampling for voltage measurement, but most of the data loggers (recorders) are not capable of fast sampling for temperature sensor. As for temperature sensors, it depends on how much sampling frequency is needed, but we measure at about 100Hz. Pressure sensors are often measured at about 100 to 1,000 Hz, depending on the situation.
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