Characterising the deformation of a polymer melt is an important task to model its processing behaviour. Knowing only shear flow properties is not sufficient to explain processing behaviour of polymers in many processes such as blown film extrusion, thermoforming, fibre spinning or blow moulding that involve stretching. As Meissner (1979) realised on different LDPE resins using only shear data can not always sufficiently explain the deformation behaviour and therefore the processing behaviour of polymers. Since the 1980s the extensional or elongational viscosity has been recognised as a very important property for processes like blown film extrusion, thermoforming or fibre spinning (Baird 1999, Wagner et al. 2002, Bhattacharya 2004). Obtained results show that the elongational viscosity is also a very sensitive indicator for long-chain branching. Measuring the extensional viscosity means getting a value for the materials resistance to stretching flow or elongational deformation. Since the first theoretical works have been made on this topic by Trouton in 1906, different measuring methods have been developed. Apart from simple methods which are not well defined and perform only indirect measurements (like the melt strength test or capillary rheometry), some more complex and precise methods have been established. The widely accepted and commercial available and therefore the most important ones are the Munstedt-type and the Meissner-type, both introduced in the 1970’s. The Munstedt-type rheometer operates via translating clamps suspended in an oil bath (Munstedt 1979) and the Meissner-type uses counter rotating belts (Meissner 1981). Both have been commercialised by Rheometrics, the Munstedt-type as the Rheometrics Extensional Rheometer (RER) in 1981 and a modified Meissner-type as the Rheometrics Melt Extensional Rheometer (RME) in 1994. The RME technique was used for various experiments such as Meissner et al. (1981, 1982), Meissner (1985), Meissner and Hostettler (1994), Levitt and Macosko (1997), Wagner et al. (1998, 2000, 2002), Schulze at al. (2001).
Nevertheless there are different problems occurring with the RME device discussed in various papers e.g. by Meissner (1994), Schweizer (2000), Schulze at al. (2001) and Barroso et al. (2002). [...]
Inhaltsverzeichnis (Table of Contents)
- Abstract
- Nomenclature
- Introduction
- Background
- Objectives
- Materials and equipment
- Materials
- Polystyrene
- Polypropylene
- PPNC
- Equipment
- ARES rotational rheometer
- CEAST Modular Melt Indexer
- RME extensional rheometer
- MDSC 2920 calorimeter
- Experimental Methods
- Introduction to rheology
- Shear rheology
- Sample preparation
- Steady shear measurement
- Dynamic measurement
- Melt Density
- Extensional rheology
- Sample preparation
- Measurement
- Visual analysis
- DSC
- Results & discussion
- Shear testing
- DSC
- Extensional testing
- Error analysis
- Error calculation for video analysis
- Comparison of PP and PPNC
- Conclusions
- References
- Appendix
Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)
This work aims to improve measurement and analysis techniques for melt extensional rheometry. It investigates the extensional viscosity of different polymer melts, focusing on the challenges and limitations of existing methods. The study contributes to a better understanding of polymer processing behavior, especially in processes involving stretching flows.
- Improved measurement techniques for melt extensional rheometry
- Analysis of extensional viscosity in different polymer melts (Polystyrene, Polypropylene, Polypropylene nanocomposite)
- Comparison of different rheological measurement methods
- Error analysis and improvement of data accuracy
- Relationship between rheological properties and polymer processing behavior
Zusammenfassung der Kapitel (Chapter Summaries)
Introduction: This chapter provides background information on the importance of characterizing the deformation of polymer melts, particularly in processes involving stretching flows like blown film extrusion or fiber spinning. It highlights the limitations of using only shear flow properties and emphasizes the significance of extensional viscosity as a key material property. The chapter also reviews existing extensional rheometry techniques, including the Munstedt-type and Meissner-type rheometers, which are widely accepted for their accuracy and precision.
Materials and equipment: This chapter details the materials and equipment used in the study. The polymers investigated include Polystyrene (PS), Polypropylene (PP), and Polypropylene nanocomposite (PPNC). The experimental setup includes various rheometers, a calorimeter, and associated instruments for sample preparation and data acquisition. The detailed descriptions are critical for reproducibility and for understanding the specific experimental conditions influencing the results.
Experimental Methods: This section comprehensively describes the experimental procedures employed. It covers fundamental rheological principles, detailing both shear and extensional rheometry techniques. The chapter elaborates on sample preparation methods, measurement techniques (including steady and dynamic shear measurements, melt density determination, and visual analysis of extensional flows), and data acquisition protocols. The discussion of DSC (Differential Scanning Calorimetry) integrates thermal characterization into the broader rheological analysis.
Results & Discussion: This chapter presents and interprets the results of the experimental work. It analyzes the shear and extensional rheological data obtained from the different polymers and discusses the observed trends and relationships between material properties and processing behavior. Error analysis and its impact on data interpretation are thoroughly examined. A key aspect is the comparison of the rheological behavior of PP and PPNC, providing insights into the effects of nano-reinforcement on extensional flow properties.
Schlüsselwörter (Keywords)
Melt extensional rheometry, extensional viscosity, polymer melts, polypropylene, polystyrene, polypropylene nanocomposite, shear rheology, rheological measurements, error analysis, polymer processing, material characterization, differential scanning calorimetry (DSC).
Frequently Asked Questions: Comprehensive Language Preview on Melt Extensional Rheometry
What is the main focus of this study?
This study focuses on improving measurement and analysis techniques for melt extensional rheometry. It investigates the extensional viscosity of different polymer melts (Polystyrene, Polypropylene, and Polypropylene nanocomposite), highlighting the challenges and limitations of current methods. The aim is to better understand polymer processing behavior in processes involving stretching flows.
What materials were used in the experiments?
The polymers investigated include Polystyrene (PS), Polypropylene (PP), and Polypropylene nanocomposite (PPNC).
What equipment was used in the experiments?
The experimental setup included an ARES rotational rheometer, a CEAST Modular Melt Indexer, an RME extensional rheometer, and an MDSC 2920 calorimeter, along with associated instruments for sample preparation and data acquisition.
What are the key themes explored in this study?
Key themes include improved measurement techniques for melt extensional rheometry, analysis of extensional viscosity in different polymer melts, comparison of different rheological measurement methods, error analysis and improvement of data accuracy, and the relationship between rheological properties and polymer processing behavior.
What rheological measurements were performed?
Both shear and extensional rheological measurements were performed. Shear rheology involved steady shear and dynamic measurements. Extensional rheology included sample preparation, measurement, and visual analysis. Melt density was also determined. Differential Scanning Calorimetry (DSC) was used for thermal characterization.
What methods were used for sample preparation?
The document details sample preparation methods for both shear and extensional rheological measurements, but the specific procedures are not provided in this preview.
How was error analysis conducted?
The study includes a thorough examination of error analysis and its impact on data interpretation, specifically mentioning error calculation for video analysis in extensional testing. However, the specific methods are not detailed in this preview.
What is the significance of comparing PP and PPNC?
A key aspect of the study is the comparison of the rheological behavior of PP and PPNC to provide insights into the effects of nano-reinforcement on extensional flow properties.
What are the key findings or conclusions (as previewed)?
The preview does not present specific quantitative results but highlights the analysis of shear and extensional rheological data, discussion of observed trends and relationships between material properties and processing behavior, and the impact of error analysis on data interpretation. The detailed conclusions are presented in the full document.
What are the keywords associated with this study?
Keywords include Melt extensional rheometry, extensional viscosity, polymer melts, polypropylene, polystyrene, polypropylene nanocomposite, shear rheology, rheological measurements, error analysis, polymer processing, material characterization, and differential scanning calorimetry (DSC).
Where can I find a more detailed explanation of the experimental procedures?
The full document contains comprehensive descriptions of the experimental procedures, including details on sample preparation, measurement techniques, and data acquisition protocols. This preview offers a high-level overview.
What is the overall contribution of this work?
The study contributes to a better understanding of polymer processing behavior, especially in processes involving stretching flows, by improving measurement and analysis techniques for melt extensional rheometry.
- Quote paper
- Dipl. Wirtschaftsing. Guido Krebs (Author), 2006, Improved measurement and analysis techniques for melt extensional rheometry, Munich, GRIN Verlag, https://www.grin.com/document/58506
