In Situ Detection of Interfacial Flow Instabilities in Polymer Co-Extrusion Using Optical Coherence Tomography and Ultrasonic Techniques

Hammer, Alexander; Roland, Wolfgang; Zacher, Maximilian; Praher, B.; Hannesschläger, Günther; Löw-Baselli, Bernhard; Steinbichler, Georg

doi:10.3390/polym13172880

Cited by 10 publications

(16 citation statements)

References 42 publications

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“…Commonly, flow instabilities of polymer melt flows and also interfacial co-extrusion flow instabilities are undesired because they lead to optical defects, mechanical weak spots, or layer discontinuities which might be critical for barrier and adhesive layers [24]. The interfacial flow instabilities observed in this study, however, led to considerably improved final mechanical product properties, simultaneously maintaining the two-layer structure and its optical and surface properties.…”

Section: Discussionmentioning

confidence: 73%

Improving Layer Adhesion of Co-Extruded Polymer Sheets by Inducing Interfacial Flow Instabilities

et al. 2022

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Co-extrusion is commonly used to produce polymer multilayer products with different materials tailoring the property profiles. Adhesion between the individual layers is crucial to the overall performance of the final structure. Layer adhesion is determined by the compatibility of the polymers at the interface and their interaction forces, causing for example the formation of adhesive or chemical bonds or an interdiffusion layer. Additionally, the processing conditions, such as temperature, residence time, cooling rate, and interfacial shear stress, have a major influence on the interactions and hence resulting layer adhesion. Influences of temperature and residence time are already quite well studied, but influence of shear load on the formation of an adhesion layer is less explored and controversially discussed in existing literature. In this work, we investigated the influence of different processing conditions causing various shear loads on layer adhesion for a two-layer co-extruded polymer sheet using a polypropylene and polypropylene talc compound system. Therefore, we varied the flow rates and the flow geometry of the die. Under specific conditions interfacial flow instabilities are triggered that form micro layers in the transition regime between the two layers causing a major increase in layer adhesion. This structure was analyzed using confocal Raman microscopy. Making use of these interfacial flow instabilities in a controlled way enables completely new opportunities and potentials for multi-layer products.

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Section: Discussionmentioning

confidence: 73%

Improving Layer Adhesion of Co-Extruded Polymer Sheets by Inducing Interfacial Flow Instabilities

et al. 2022

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“…The PMMA Blend and HDPE were used as top-layer melt. Their refractive indices were determined in accordance with the procedure we developed in, [44] yielding a value of 1.376 ± 0.004 and 1.387 ± 0.004, respectively.…”

Section: Co-extrusion Trial Designmentioning

confidence: 99%

Experimental validation ofnon‐Newtonianstratifiedco‐extrusionprediction models using a digital process twin

Hammer

Roland

Zacher

et al. 2022

Polymer Engineering & Sci

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In the co‐extrusion of plastics, pressure‐throughput behavior, layer distribution, and residence time are crucial parameters, modeling of which contributes to manufacturing high‐quality products at optimized process efficiency and significantly shortens development times for die systems. In previous work, we have presented symbolic regression models to predicting the (i) pressure‐throughput behavior, (ii) position of the interface, (iii) interfacial shear stress, (iv) ratio of volume flow rates, and (v) interfacial flow velocity for isothermal two‐layer co‐extrusion flows through rectangular ducts. These regression models are mathematically simple and capable of capturing the shear‐thinning nature of polymer melts without the need for numerical methods. Here, we present an experimental study validating the proposed models against co‐extrusion process data and comparing them to existing theories. To this end, a two‐layer co‐extrusion demonstration die instrumented with an optical coherence tomography sensor for detecting the interfacial position was used. To accurately set up and evaluate the die flows, the overall co‐extrusion process was represented by means of a digital process twin. Industrially relevant combinations of materials were tested under a wide range of processing conditions. Comparisons of pressure losses and interfacial positions to the predictions showed excellent agreement and the results outperformed the concept of representative viscosity.

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“…In which f is the air flow from a source, the section area of the hose is a, and the flow reduces its section area b while crossing the orifice plate. Thus, a pressure difference can be measured between points P1 and P2, moreover 𝑣 and 𝑣 represent the fluid flow speed of the air flow in the direction depicted by the red arrow [11,12]. Figure 4 shows the compact air flow sensor developed for the integrated design, which is composed of an upstream and downstream pipe welded to an orifice plate.…”

Section: Mathematical Modellingmentioning

confidence: 99%

“…In which f is the air flow from a source, the section area of the hose is a, and the flow reduces its section area b while crossing the orifice plate. Thus, a pressure difference can be measured between points P1 and P2, moreover v 1 and v 2 represent the fluid flow speed of the air flow in the direction depicted by the red arrow [11,12]. In order to find the pressure, airflow and volume equations, the Stokes equations were analyzed using Equation (1), in which, "f" is the function as the consequence of airflow and "µ" and "D" are the average velocity and dispersion coefficient, respectively [13,14].…”

Section: Mathematical Modellingmentioning

confidence: 99%

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Mathematical Analysis of a Low Cost Mechanical Ventilator Respiratory Dynamics Enhanced by a Sensor Transducer (ST) Based in Nanostructures of Anodic Aluminium Oxide (AAO)

et al. 2022

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Mechanical ventilation systems require a device for measuring the air flow provided to a patient in order to monitor and ensure the correct quantity of air proportionated to the patient, this device is the air flow sensor. At the beginning of the COVID-19 pandemic, flow sensors were not available in Peru because of the international supply shortage. In this context, a novel air flow sensor based on an orifice plate and an intelligent transducer was developed to form an integrated device. The proposed design was focused on simple manufacturing requirements for mass production in a developing country. CAD and CAE techniques were used in the design stage, and a mathematical model of the device was proposed and calibrated experimentally for the measured data transduction. The device was tested in its real working conditions and was therefore implemented in a breathing circuit connected to a low-cost mechanical ventilation system. Results indicate that the designed air flow sensor/transducer is a low-cost complete medical device for mechanical ventilators that is able to provide all the ventilation parameters by an equivalent electrical signal to directly display the following factors: air flow, pressure and volume over time. The evaluation of the designed sensor transducer was performed according to sundry transducer parameters such as geometrical parameters, material parameters and adaptive coefficients in the main transduction algorithm; in effect, the variety of the described results were achieved by the faster response time and robustness proportionated by transducers of nanostructures based on Anodic Aluminum Oxide (AAO), which enhanced the designed sensor/transducer (ST) during operation in intricate geographic places, such as the Andes mountains of Peru.

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In Situ Detection of Interfacial Flow Instabilities in Polymer Co-Extrusion Using Optical Coherence Tomography and Ultrasonic Techniques

Cited by 10 publications

References 42 publications

Improving Layer Adhesion of Co-Extruded Polymer Sheets by Inducing Interfacial Flow Instabilities

Improving Layer Adhesion of Co-Extruded Polymer Sheets by Inducing Interfacial Flow Instabilities

Experimental validation ofnon‐Newtonianstratifiedco‐extrusionprediction models using a digital process twin

Mathematical Analysis of a Low Cost Mechanical Ventilator Respiratory Dynamics Enhanced by a Sensor Transducer (ST) Based in Nanostructures of Anodic Aluminium Oxide (AAO)

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