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Rheology–Microstructure Relationships in Melt-Processed Polylactide/Poly(vinylidene Fluoride) Blends

Salehiyan, Reza; Ray, Suprakas S.; Stadler, Florian J.; Ojijo, Vincent


Reza Salehiyan

Suprakas S. Ray

Florian J. Stadler

Vincent Ojijo


In this study, small amplitude oscillatory shear tests are applied to investigate the rheological responses of polylactide/poly(vinylidene fluoride) (PLA/PVDF) blends and to correlate their viscoelastic properties with the morphological evolutions during processing. Although the analysis of the elastic moduli reveals some changes as a function of blend composition and processing time, the weighted relaxation spectra are shown to be more useful in detecting changes. The analysis demonstrates that when PVDF, i.e., the more viscous phase, is the matrix, the blend relaxes cooperatively and only a single relaxation peak is observed. By contrast, blends with highly concentrated morphologies do not fully relax, showing instead an upward increasing trend at longer times. This outcome is attributed to the broad distribution of highly concentrated droplets with a high probability of droplet–droplet contacts. Dynamic mechanical analysis (DMA) reveals that crystalline segmental motions attributed to the α-relaxation of PVDF at around 100 °C are restricted by the highly concentrated morphology of the 50/50 PLA/PVDF blend processed for 10 min. Relaxation analyses of the blends via dynamic oscillatory shear tests and DMA are shown to be powerful tools for investigating small microstructural changes in immiscible polymer blends.


Salehiyan, R., Ray, S. S., Stadler, F. J., & Ojijo, V. (2018). Rheology–Microstructure Relationships in Melt-Processed Polylactide/Poly(vinylidene Fluoride) Blends. Materials, 11(12), Article 2450.

Journal Article Type Article
Acceptance Date Nov 7, 2018
Online Publication Date Dec 3, 2018
Publication Date 2018
Deposit Date Jan 30, 2023
Publicly Available Date Jan 31, 2023
Print ISSN 1996-1944
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 11
Issue 12
Article Number 2450
Keywords PLA/PVDF blend; rheology; processing-driven morphology


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