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Polystyrene Glasses under Compression: Ductile and Brittle Responses.
Jianning Liu1, Panpan Lin1, Shiwang Cheng2
1Department of Polymer Science, University of Akron, Akron, Ohio 44325, United States.
ACS Macro Letters
|May 26, 2022
Summary
Adding high molecular weight polystyrene enhances ductility in mixtures, making them ductile well below their glass transition temperature. This molecular weight effect on mechanical properties is linked to chain networking.
Area of Science:
- Polymer Science
- Materials Science
- Mechanical Engineering
Background:
- Polystyrene (PS) exhibits temperature-dependent mechanical behavior.
- Understanding the influence of molecular weight on PS ductility is crucial for material applications.
Purpose of the Study:
- To investigate the mechanical responses of polystyrene with varying molecular weights and mixtures under uniaxial compression.
- To elucidate the role of molecular weight and molecular weight distribution in polystyrene's yielding and plastic flow behavior.
Main Methods:
- Uniaxial compression tests were performed on polystyrene samples of different molecular weights (M_w) and their binary mixtures.
- Experiments were conducted across a range of temperatures, including below the glass transition temperature (T_g).
Main Results:
- Polystyrene with M_w = 25 kg/mol showed brittle behavior above its T_g.
- Incorporating a high molecular weight component significantly increased ductility in PS mixtures, extending ductile behavior over 40°C below T_g.
- High molecular weight PS (M_w = 319 kg/mol) exhibited yielding and plastic flow even at -70°C.
Conclusions:
- The mechanical responses of polystyrene are strongly dependent on molecular weight and molecular weight distribution.
- Chain networking is identified as the primary mechanism responsible for yielding and plastic compression in polystyrene.
- Tailoring molecular weight and distribution offers a pathway to control the ductility and mechanical performance of polystyrene materials.
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