Cross-Linking of Poly(butylene terephthalate) by Reactive Extrusion Using Zn(II) Epoxy-Vitrimer Chemistry

• Published in: Macromolecules Vol. 50; no. 16; pp. 6117 - 6127
• Main Authors: Demongeot, Adrien, Groote, Ramon, Goossens, Han, Hoeks, Theo, Tournilhac, François, Leibler, Ludwik
• Format: Journal Article
• Language: English
• Published: American Chemical Society 22.08.2017
• Subjects: Chemical Sciences; Polymers
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.7b01141

Poly­(butylene terephthalate) (PBT) vitrimers were prepared by reactive extrusion from industrial PBT thermoplastics using Zn­(II)-catalyzed addition and transesterification chemistry. PBT thermoplastics are characterized by a high degree of crystallinity, high melting temperature, and high crystallization rate, but right above their melting temperature their mechanical resistance disappears and they show a tendency to drip. We compared −OH and −COOH end-group additions on epoxies in the presence of two different catalysts: 2-methyl­imidazole (2-MI) and zinc acetyl­acetonate (Zn­(acac)2). With 2-MI, chain extension reactions were efficiently catalyzed in a few minutes at 270 °C, but no gelation was observed. With Zn­(acac)2, −COOH addition and transesterification led to efficient cross-linking within a few minutes at 270 °C. Such cross-linked material combines the crystalline properties of PBT and dimensional stability above the melting temperature. PBT materials cross-linked through epoxy-vitrimer chemistry are not soluble. However, compared with radiation cross-linked PBT, vitrimer PBT is processable and can be reshaped and recycled.