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Process-Relevant Flow Characteristics of Styrene-Based Thermoplastic Elastomers and Their Representation by
Markus Kaempfe1, Matthieu Fischer1, Ines Kuehnert1
1Leibniz-Institut für Polymerforschung Dresden e.V., D-01069 Dresden, Germany.
Polymers
|September 9, 2023
Summary
Thermoplastic elastomers (TPSs) exhibit complex flow behaviors that challenge standard rheometric data. Their multiphase morphology significantly impacts processing, limiting the reliability of conventional characterization methods.
Area of Science:
- Polymer Science
- Materials Science
- Rheology
Background:
- Thermoplastic elastomers (TPSs) based on styrene-block copolymers possess complex multiphase morphologies.
- These morphologies significantly influence their flow behavior, often overlooked by standard characterization techniques.
- Understanding non-Newtonian flow phenomena is crucial for accurate rheometric data in TPS processing.
Purpose of the Study:
- To evaluate the relevance of non-Newtonian flow phenomena for the validity of rheometric data in thermoplastic elastomer (TPS) processing.
- To assess the reliability of commonly used characterization and evaluation procedures for TPSs.
- To investigate the impact of shear and geometrical conditions on the rheological behavior of TPSs.
Main Methods:
- Characterization of three commercial TPSs with similar hardness (approx. 60 Shore A) but different applications.
- Utilized parallel plate and high-pressure capillary rheometry for material characterization.
- Employed computational fluid dynamics (CFD) simulations to model capillary rheometer flow and assess data validity.
Main Results:
- TPSs displayed distinct rheological behaviors influenced by shear and geometrical conditions.
- A disproportionate increase in pressure loss (up to one third) was observed when doubling capillary diameter for the lowest viscosity TPS.
- CFD simulations failed to reproduce the capillary flow of the lowest viscosity material, indicating simulation limitations or material complexities.
Conclusions:
- Conventionally determined rheometric data for TPSs have limited applicability in evaluating process flows across different material grades.
- The complex multiphase morphology of TPSs necessitates advanced evaluation methods beyond standard rheometry.
- Non-Newtonian flow phenomena and geometric effects play a critical role in TPS processing, impacting data interpretation.
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