Investigation of the thermal degradation of fully aromatic regular polyesters: Poly(oxy-1,4-phenyleneoxy- fumaroyl-bis-4-oxybenzoate) Fabio Bertini a , Vjacheslav V. Zuev b, * a Istituto per lo Studio delle Macromolecole e C.N.R., Via Bassini 15, Milano 20133, Italy b Institute of Macromolecular Compounds of the Russian Academy of Sciences, Bolshoi pr. 31, Sankt Petersburg 199004, Russian Federation Received 21 March 2006; received in revised form 9 June 2006; accepted 12 July 2006 Available online 8 September 2006 Abstract The thermal behaviour and degradation mechanism of fully aromatic polyester, poly(oxy-1,4-phenyleneoxy-fumaroyl-bis-4-oxybenzoate), were studied by pyrolysisegas chromatography and pyrolysisegas chromatography/mass spectrometry at 500e700  C, and by thermogravim- etry. The influence of fullerene C 60 additives on thermal behaviour and thermal degradation was investigated. On the basis of pyrolysis products determined, the origin of the main degradation products (maleic anhydride, phenol, hydroquinone, phenyl ether, p-hydroxybenzoate-p 0 -phenol, etc.) was estimated. The fullerene is a well-known efficient acceptor of radicals and its presence influences the thermal degradation process of polymers shifting the decomposition from a radical pathway to a non-radical mechanism. Thermal degradation mechanism of poly(oxy-1,4-phe- nyleneoxy-fumaroyl-bis-4-oxybenzoate) is discussed in detail. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Poly(oxy-1,4-phenyleneoxy-fumaroyl-bis-4-oxybenzoate); Fullerene C 60 ; Pyrolysisegas chromatography; Thermal behaviour; Thermal degradation mechanism 1. Introduction Aromatic polyesters are increasingly replacing other con- ventional materials in engineering applications requiring high strength to weight ratio, high temperatures, and good chemical resistance. Liquid crystalline polymeric (LCP) mate- rials are emerging as engineering resins due to their unique molecular arrangement. A large variety of LCP systems have been examined [1]. Due to their rigidity and anisotropy, LCPs have improved physical properties, including high me- chanical properties in the direction of orientation, low thermal shrinkage, high dimensional stability, and low viscosity during processing. As LCP materials random aromatic polyesters like Vectra Ò (copolymer of p-oxybenzoic and 2,6-oxynaphthoic acids), Xydar Ò (polyethylene terephthalate modified by p-oxy- benzoic acid) and others are used commercially. Their thermal behaviour was investigated in various publications [2,3] but the thermal degradation mechanism was never determined. A significant hindrance to the degradation mechanism studies is the random unit distribution in these copolymers that com- plicates the determination of kinds and sequences of the deg- radation reactions. Nonetheless, the clarification of degradation mechanism is relevant to the deterioration of properties of the materials during high-temperature process- ing. For this purpose we synthesized regular fully aromatic polyester, poly(oxy-1,4-phenyleneoxy-fumaroyl-bis-4-oxy- benzoate) (I), and its thermal behaviour and degradation mechanism have been investigated by thermogravimetric anal- ysis in dynamic conditions and by pyrolysisegas chromatog- raphy techniques in isothermal conditions. * Corresponding author. Tel.: þ7 812 3284001; fax: þ7 812 3286869. E-mail address: zuev@hq.macro.ru (V.V. Zuev). 0141-3910/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymdegradstab.2006.07.008 Polymer Degradation and Stability 91 (2006) 3214e3220 www.elsevier.com/locate/polydegstab