Crystal morphology and non-isothermal crystallization kinetics of polyvinylidene fluoride used as a pressure barrier in flexible pipes: nanoclay effect

• Published in: Iranian polymer journal Vol. 31; no. 6; pp. 677 - 690
• Main Authors: de Lima, Mayara S. Cândido F., da Silva, Antonio Henrique Monteiro da Fonseca Thomé, da Costa Neto, Célio A., Nascimento, Christine Rabello, de Andrade, Mônica Calixto, Bertolino, Luiz Carlos, da Silva, Ana Lúcia Nazareth
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.06.2022; Springer Nature B.V
• Subjects: Ceramics; Chemistry; Chemistry and Materials Science; Composites; Crystal morphology; Crystallization; Flexible pipes; Fluorides; Glass; Hybrid systems; Internal pressure; Kinetics; Molecular structure; Montmorillonite; Morphology; Nanocomposites; Natural Materials; Original Research; Polymer Sciences; Polyvinylidene fluorides; Sheaths; Vinylidene fluoride; Flexible pipe; Non-isothermal crystallization; Polyvinylidene fluoride; Montmorillonite; Composite
• ISSN: 1026-1265; 1735-5265
• DOI: 10.1007/s13726-021-01008-6

Poly(vinylidene fluoride) (PVDF) is a commercial polymer used as an internal pressure sheath for offshore flexible pipes. A hybrid system based on PVDF was developed for offshore applications with 1, 2.5 and 5% by weight of nanoclay grade montmorillonite (OMMT) (polar and non-polar grades) by melting processing. The study was based on the effect of nanoclay grades on the molecular structure and the non-isothermal crystallization kinetics of the PVDF matrix by Jeziorny and Mo methods. The XRD results suggested that nanocomposites with lower OMMT contents, polar and non-polar grades, showed exfoliated morphology and are promising materials to be applied as pressure barrier in offshore applications. The DSC data showed that both OMMTs decreased the nanocomposite crystallinity, whereas the nanocomposite with polar OMMT grade showed less reduction in these values, probably due to a greater interaction with the PVDF matrix compared to a non-polar OMMT. The non-isothermal crystallization results showed that at 1% by weight OMMT (polar and non-polar grades) content, the nanocomposites have t 1/2 values lower than neat PVDF, while the PVDF/OMMT nanocomposites with 5% by weight OMMT content (polar and non-polar grades) have higher T c p and t 1/2 values compared to neat PVDF, indicating that the nanoclays at 5% by weight content act as a nucleating agent, but decrease the crystallization rate. The Jeziorny and Mo models were adequate to describe the non-isothermal crystallization kinetics of PVDF and its nanocomposites. The two models applied showed that the addition of both nanoclay grades decreases the crystallization rate of PVDF in the nanocomposites. Graphical abstract