Leistritz launches new elongational rheometer for accurate process control
Manufacturer of extrusion technology, Leistritz, has launched a new elongational rheometer that it says provides solid data to prove even the slightest variations in the compounding process.
Unveiled to the plastics industry for the first time at the Fakuma trade fair in Southern Germany in October, the new state-of-the-art measuring system is designed to provide optimum control over the extrusion process.
“As part of the continuous development of process technology and our Industry 4.0 activities, we paid close attention to the important issue of an intelligent process control,” explained Thomas Unger, Head of the Leistritz Leistritz lab in Nuremberg. “In cooperation with the Austrian Johannes Kepler University in Linz we developed an online elongational rheometer with patented die geometry.”
The range of applications for the new rheometer extends to all plastics and is reliable in processes from highly viscous pipe compounds to low viscous products for fibre and injection moulding.
During the extrusion process, a small amount of the melt flow is channeled off via a bypass system and pushed through the rheometer’s slot die. This die is based on a new, patented design with a hyperbolic narrowing. After the measurement, the material is transferred back into the process without losing any material.
The rheometer allows online measuring of the shear viscosity with shear rates in the range of 10 to 10,000 s-1 and the elongational viscosity with elongation rates in the range of 5 to 75 s-1. The die generates a constant elongational flow, something Leistriz says was previously not possible with current online measurement devices. During a continuous measuring process, the operator can query two measured values of shear viscosity and one value of extensional viscosity in the according, precisely defined shear and expansion ranges at the same time.
“An intelligent automation in the online rheometer’s control unit allows the customer to obtain viscosity curves of the material being currently processed within a very short time. This is accomplished through targeted variation of the shear and elongational rates,” continued Unger. Additionally, the elongational rheometer can also indicate the melt flow index as well as the IV value. The wide range of online analysis options is complemented by the determination of the melt density, Leistriz says.
The online rheometer can be mechanically integrated onto any given extrusion process, without having to undergo major retrofits. The software and visualisation of the measured results is either part of the Leistritz extruder control unit of a separate stand-alone version.
“The online process and quality control has increasingly become an indispensable asset in the extrusion process, because it provides quick and efficient monitoring, which past installations of this measuring system have shown,“ says Unger.