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Rheology⁻Microstructure Relationships in Melt-Processed Polylactide/Poly(vinylidene Fluoride) Blends
Reza Salehiyan1, Suprakas Sinha Ray2,3, Florian J Stadler4
1DST-CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa. RSalehiyan@csir.co.za.
Investigating polylactide/poly(vinylidene fluoride) (PLA/PVDF) blends reveals that relaxation spectra effectively detect microstructural changes. Highly concentrated morphologies hinder relaxation, impacting blend properties during processing.
Area of Science:
- Polymer Science
- Materials Science
- Rheology
Background:
- Immiscible polymer blends require understanding rheological behavior for property prediction.
- Morphological evolution significantly influences viscoelastic properties during processing.
Purpose of the Study:
- To investigate the rheological responses of polylactide/poly(vinylidene fluoride) (PLA/PVDF) blends.
- To correlate viscoelastic properties with morphological changes during processing.
- To identify sensitive methods for detecting microstructural alterations.
Main Methods:
- Small amplitude oscillatory shear tests were employed to analyze blend rheology.
- Dynamic mechanical analysis (DMA) was used to assess thermal and mechanical properties.
- Weighted relaxation spectra were utilized to interpret viscoelastic data.
Main Results:
- Weighted relaxation spectra proved more effective than elastic moduli in detecting microstructural changes.
- Blends with poly(vinylidene fluoride) (PVDF) as the matrix exhibited cooperative relaxation with a single peak.
- Highly concentrated morphologies showed incomplete relaxation, attributed to increased droplet-droplet contacts.
- DMA indicated restricted crystalline segmental motions in the 50/50 PLA/PVDF blend due to morphology.
Conclusions:
- Relaxation analysis via oscillatory shear and DMA are powerful tools for studying microstructural changes in immiscible polymer blends.
- Morphology significantly impacts the relaxation behavior and viscoelastic properties of PLA/PVDF blends.
- Understanding these relationships is crucial for tailoring blend performance in various applications.
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