Mechanical enhancement of melt-stretched β-nucleated isotactic polypropylene: The role of lamellar branching of β-crystal |
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| Institution: | 1. College of Materials Science and Engineering, The Key Laboratory of Advanced Materials Processing and Mold of Ministry of Education, Zhengzhou University, Zhengzhou, PR China;2. Institute of Polymer Materials, Friedrich-Alexander University Erlangen-Nuremberg, Martensstrasse 7, 91058 Erlangen, Germany;3. China Astronauts Research and Training Center, Beijing 100089, China;4. Integrated Composites Laboratory (ICL), Department of Chemical & Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, United States;1. Department of Physical Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic;2. Institute of Chemical Process Fundamentals, Academy of Sciences of the Czech Republic, Rozvojová 135, 165 02 Prague 6, Czech Republic;3. Institute on Membrane Technology, ITM-CNR, Via P. Bucci, Cubo 17/C, 87036 Rende, CS, Italy;4. Solvay Specialty Polymers, R&D Center, Bollate, MI, Italy;1. Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy;2. Chem.Co Consultant, Via J.F.Kennedy 2, 45030 Occhiobello (RO), Italy;1. Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409, USA;2. Department of Polymer Science and Engineering, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing 100083, PR China;3. Beijing National Laboratory for Molecular Sciences, Joint Laboratory of Polymer Science and Materials, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China;1. Chengxian College, Southeast University, Nanjing, Jiangsu 210088, PR China;2. College of Chemical and Engineering, Southeast University, Nanjing, Jiangsu, 211189, PR China |
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| Abstract: | Melt-stretched isotactic polypropylene (iPP) filled with different weight fractions (0, 0.1, 0.2 and 0.4 wt %) of β-nucleating agent (β-NA) was extruded via a single screw extruder with a slit die and immediately melt-stretched at the die exit. The microstructure and mechanical properties (i.e., monotonic tensile, step-cycle and stress relaxation behavior) of these samples were analyzed. Unexpectedly, the lamellar branching of β-crystal, which is similar to lamellar branching of α-crystal, is observed in melt-stretched β-nucleated iPP. More interestingly, it is found that, compared with other samples, iPP containing 0.2 wt % of β-NA has the best mechanical properties. Through thorough analysis of various structural characterizations, the improved tensile strength obtained from step-cycle tests and viscous force obtained from stress relaxation measurements for iPP with 0.2 wt% of β-NA is ascribed to lamellar branching of β-crystal. The study is an example of preparing high performance polymers via practical polymer processing methods. |
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| Keywords: | Isotactic polypropylene β-nucleating agent Lamellar branching Step-cycle test Stress relaxation |
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