The effect of curing temperatures on the thermal behaviour of new polybenzoxazine-modified epoxy resin

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The effect of curing temperatures on the thermal behaviour of new polybenzoxazine‑modified epoxy resin Abdulrahman Musa1 · Khalid A. Alamry1   · Mahmoud A. Hussein1,2 Received: 10 October 2019 / Revised: 12 November 2019 / Accepted: 16 November 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019

Abstract In this study, hydroxyl end functional group benzoxazine monomer (BZ-OH) was synthesized from ethanolamine, bisphenol-A and paraformaldehyde. The monomer was analysed and confirmed by Fourier transform infrared, and (1H and 13C) nuclear magnetic resonance techniques, respectively. The benzoxazine (10% by weight) was incorporated into a (50:50) weight ratio of epoxy resin and its hardener. This mixture was first cured at room temperature for 24  h and then post-cured at temperatures; 90, 120, 150, 180, 200 and 220  °C, respectively. Thermal gravimetric analysis was employed to study the effect of the  different curing temperatures on the thermal properties of the benzoxazine/epoxy mixture. The results showed an overall improvement in the thermal stability of the samples as the curing temperature is increased. However, the product cured at 220  °C depicted a better thermal behaviour, with a decomposition temperature in the range of 258–532 °C. Keywords  Polybenzoxazine · Epoxy resin · Curing temperatures · Thermal behaviour · Scanning electron microscopy

Introduction Epoxy resin is one of the engineering polymer materials with many industrial applications. This includes its use such as a  coating and adhesive substances, material for semiconductor manufacturing and other applications [1]. The versatility of the resin is due to its promising chemical, mechanical and thermal properties. However, these properties depend on the curing temperature of the resin [2]. Epoxy suffers * Abdulrahman Musa [email protected] * Khalid A. Alamry [email protected] 1

Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia

2

Chemistry Department, Assiut University, Synthetic Polymer Lab. 122, Assiut 71516, Egypt



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some drawbacks because of its brittleness, notch sensitivity and lack of toughness, thus limiting its wider applicability. Current researches on this material also include; improving the behaviour of the resin by using different toughening methods. Reported works on this resin show successful modification of the material using polymers [3–7], nanoparticles [8, 9], natural and synthetic fibres [10–12]. Benzoxazine is a monomer belonging to the class of phenolic resins. The monomer is synthesized by the reaction of primary amines, phenols and formaldehydes [13]. Polymerization of this phenolic resin, under carefully designed conditions, gives polybenzoxazine [14]. Like epoxy resin, polybenzoxazine has attractive properties such as effective heat stability and excellent resistance to chemical attack [15], low water absorption [16], high strength and glass transition temperatures [17]. Also, curing of benzoxazines does not