Malaysian Journal of Analytical Sciences Vol 21 No 2 (2017): 356 - 364

DOI: https://doi.org/10.17576/mjas-2017-2102-10

 

 

 

MORPHOLOGICAL PROPERTIES OF POLY(VINYLIDENE FLUORIDE-CO-TETRAFLUOROETHYLENE MEMBRANE): EFFECT OF SOLVENTS AND POLYMER CONCENTRATIONS

 

(Sifat–Sifat Morfologi Membran Kepingan Rata Poli(Vinilidena Fluorida-Ko Tetrafluoridaetilena): Kesan Pelarut dan Kepekatan Polimer)

 

Amira Mohd Nasib*, Irfan Hatim, Nora Jullok, Hameed R. Alamery

 

School of Bioprocess Engineering,

Universiti Malaysia Perlis, 02600 Arau, Perlis, Malaysia

 

*Corresponding author: amira.m.nasib@gmail.com

 

 

Received: 26 August 2016; Accepted: 8 January 2017

 

 

Abstract

Poly(vinylidene fluoride-co-tetrafluoroethylene) (PVDF-co-PTFE) flat sheet membranes were prepared via phase inversion  process by means of immersion precipitation. The effects on the microstructure of prepared membranes by using different solvents and the effect of polymer solution composition (polymer concentration) on the membrane morphologies and the membrane porosity were studied. Three different solvents were employed, which were, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF). Different polymer concentrations were used; 20 wt.%, 25 wt.% and 30 wt.%. Brookfield viscometer was used to measure the viscosity for each polymer solution before the membrane was casting. The morphological study for the cross-sectional area of PVDF-co-PTFE membrane was carried out by using scanning electron microscope (SEM). The membrane porosity was determined by using the weight difference and density resulted from the immersing of dry membrane into octanol for 15 seconds. The results showed that the polymer concentration was a particularly important parameter. At different polymer concentration, the precipitant plays an important role and finally influence the prepared membrane microstructure. At higher concentration of PVDF-co-PTFE polymer, the prepared membrane possessed a sponge-like membrane structures, whereas at lower concentration, a finger-like structure was obtained. It was also found that, the membrane porosity decreases with the increasing of polymer concentration. The effect of different solvent reflected to different morphologies of the prepared flat sheet membranes. Prepared membrane with more sponge-like structure indicated a weak dissolution solvent was used. Hence, a small amount of water needed to induce precipitation and reduced the precipitation rate.

 

Keywords:  PVDF-co-PTFE polymer, phase inversion, polymer concentration, membrane morphology

 

Abstrak

Membran kepingan rata poli (vinilidena fluorida-ko-tetrafluoridaetilena) (PVDF-ko-PTFE) telah disediakan dengan kaedah fasa penyongsangan menggunakan fasa pemisah bukan pelarut teraruh (FPBT). Kesan ke atas mikrostruktur membran tersedia dengan menggunakan pelarut yang berbeza dan kesan komposisi larutan penuangan (kepekatan polimer) ke atas morfologi membran dan keliangan membran telah dikaji. Tiga pelarut yang berbeza digunakan ialah N,N-dimetilasetamida (DMAs), N-metil-2-pirolidon (NMP) dan N,N-dimetilformamida (DMF). Kepekatan polimer yang berbeza akan digunakan, iaitu pada 20 wt.%, 25 wt.% dan 30 wt.%. Brookfield viskometer digunakan untuk mengukur kelikatan lasrutan polimer sebelum membran diacukan. Kajian morfologi bagi kawasan keratan rentas membran PVDF-co-PTFE telah dijalankan dengan menggunakan mikroskop elektron pengimbas (SEM). Analisis keputusan keliangan ditentukan dengan  perendaman membran kering di dalam oktanol selama 15 saat. Keputusan menunjukkan bahawa kepekatan polimer adalah parameter penting. Pada kepekatan polimer yang berbeza, bahan pemendak memainkan peranan yang penting dan akhirnya mempengaruhi mikrostruktur membran tersedia. Pada kepekatan polimer PVDF-ko-PTFE yang lebih tinggi, membran tersedia memiliki struktur membran seperti span, sedangkan pada kepekatan yang lebih rendah, struktur seperti-jejari telah diperolehi. Ia juga mendapati bahawa, keliangan membran menurun dengan peningkatan kepekatan polimer. Penggunaan pelarut yang berbeza terkesan kepada berlainan morfologi membran kepingan rata yang tersedia. Membran tersedia dengan struktur seperti span menunjukkan pelarut pelarutan lemah telah digunakan. Oleh itu, jumlah air yang sedikit diperlukan untuk mendorong mendakan dan mengurangkan kadar mendakan.

 

Kata kunci:  PVDF-ko-PTFE polimer, fasa pemisah, kepekatan polimer, morfologi membran

 

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