PROCESSING | INLINE MEASUREMENT Booming market
Rheological test instrument supplier Göettfert says the online rheometer market is booming. “Due to a general shortage of qualified personnel to take manual measurements, as well as the market moving towards even larger extruders that produce more material in shorter time spans, the need to get measurements automated and in real time is becoming increasingly evident,” says Tim Haake, General Manager, Goettfert in the US. “Online, or sometimes called inline, rheometers, measure viscosity continu- ously. While this would be sufficient to track the performance of the process, most users want to correlate viscosity to a melt
Above: Göettfert’s Mini Bypass Rheograph (MBR) compact inline rheom- eter is said to be affordable and flexible
index, because this number has been around for a long time and is a standard for the industry in quality control. With those measurements, we can follow transitions from one product to the next in the product wheel and allow the release of ‘good’ material as soon as it happens. Along the same lines, we can alarm the control room if there is a problem in production and the melt index drifts out of the set acceptable range,” he says. “Customers that buy plastic pellets and process
Right: The Real Time Rheom- eter (RTR/RTS) from Göttfert is aimed at
compounders running a wide range of melt indexes on high throughput extruders
them further typically add a shear history and with it, an additional heat cycle. As this may impact the performance of the material, manufacturers of pellets often need to take that into consideration. Again, it is possible to go down the route of measuring this in the laboratory or send the pellets straight from the pelletiser to an atline rheometer. In this situation, a small extruder, typically sitting close to the production line, re-melts the pellets and the material is run through another online rheometer,” says Haake. The drive towards for greater automation, better quality control, lower cost, and the need to be prepared for Industry 4.0, is also a factor in accelerating the move away from the laboratory towards process measurement, Haake says. To meet this trend, the company has developed the Mini Bypass Rheograph (MBR). It says its open discharge system makes it a highly suitable instrument for applications that require easy access, which is particularly useful to meet FDA rules regarding cleanli- ness or where you do not want to return the measured material to the production stream. It also appeals to recyclers, where
34 COMPOUNDING WORLD | November 2021
affordability and flexibility is important — the measurement head can be removed from an extruder and placed on another one, if required, with little downtime. Göttfert describes the MBR as a compact online capillary rheometer for continuous measurement of melt flow rate and viscosity. The instrument is around 150 mm wide and weighs 30kg, which the company claims makes it one of the smallest online rheometers available. Depending on the operating mode, a number of measurements are possible. These include melt index (MFR) or melt volume index (MVR) with or without temperature compen- sation, as well as Flow Rate Ratio (FRR) — FFR is the ratio of two consecutive MFR/MVR measurements that correspond to laboratory tests with different weights. Apparent shear rate, shear stress and viscosity can also be measured. The company also offers its Real Time Rheom-
eter (RTR/RTS), which is a suitable for processors running a wide range of melt indexes on high throughput extruders, as well as control of reactive extrusion processes. It is a continuously measuring capillary rheometer for use in online quality control and, due to its internal bypass, is said to be capable of collecting near-instantaneous data points. As a return melt system, the RTR supports reintroduction of the measured melt to the production line after testing. “With extremely long lead times for extruders these days, an online rheometer is often just a small piece added on to the overall project,” says Haake. “However, this leads to older extruders being sought out to be revamped and the online rheom- eter now becomes the focus of new projects to drive cost down and quality up.”
Compound potential German instrumentation specialist ColVisTec says that the plastics com- pounding industry has now started to understand the potential of inline measurement equipment in production and is catching up with other industries in terms of implementation. “We see two areas with distinct potential in plastics compounding - process and product development and continuous 24/7 production control,” says Fuat Eker, Director of Sales, Marketing and Customisation. “As a development tool it is our experience that inline measurement systems allow for a rapid interac- tive process by giving immediate
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IMAGE: GÖETTFERT
IMAGE: GÖTTFERT
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