Evaluating a four-directional benzene-centered aliphatic polyamine curing agent for epoxy resins
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Evaluating a four-directional benzene-centered aliphatic polyamine curing agent for epoxy resins Isothermal curing behavior and dynamic mechanical property Jintao Wan • Cheng Li • Zhi-Yang Bu Hong Fan • Bo-Geng Li
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Received: 2 April 2012 / Accepted: 3 December 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract A four-directional benzene-centered aliphatic polyamine, MXBDP, with high functionality and low volatility, is used to cure epoxy resin (DGEBA). Herein we originally report the isothermal cure kinetics and dynamic mechanical properties of DGEBA/MXBDP. Differential scanning calorimetry confirms that MXDBP is more reactive than commercial linear metaxylenediamine and branched Jeffamine T-403 and the isothermal curing reaction is autocatalytic. The Kamal model is found to be able to well describe the curing rate up to the onset of diffusion control, and the excellent match over the whole conversion range is achieved using the extended Kamal model. Interestingly, the isoconversional kinetic analysis indicates that the effective reaction activation energy (Ea) changes substantially with conversion, and ultimately decreases to a very small value (\10 kJ mol-1) because of the diffusion-controlled reaction kinetics. Then, dynamic mechanical analysis reveals that DGEBA/MXBDP exhibits the higher a- and b-relaxation temperatures and the much higher crosslink density than DGEBA/metaxylenediamine. Our experiment results support that MXBDP has the high reactivity and improved thermal resistance in combination with the advantages of the high functionality, low volatility and decreased CO2 absorption. Therefore, MXBDP may be
J. Wan C. Li Z.-Y. Bu H. Fan (&) B.-G. Li (&) State Key Laboratory of Chemical Engineering, Department of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou 310027, China e-mail: [email protected] B.-G. Li e-mail: [email protected] J. Wan Zhejiang Jiamin Plastics Company Ltd., Jiaxing 314027, China
especially suitable for room temperature-cure epoxy coatings and adhesives. Keywords Epoxy resin Aliphatic polyamine Reactivity Isothermal cure Reaction kinetics Dynamic mechanical properties
Introduction Epoxy resins possess many attractive properties such as high adhesion, mechanical strength, thermal resistance, low shrinkage during cure, excellent processability and high performance/cost ratio, etc., and thus they find many irreplaceable applications in industrial, civil and military aspects. Although many kinds of epoxy resins with different molecular structures are commercially available, the most commonly used belongs to oligomers of diglycidylether of bisphenol A (DGEBA) of varied molecular masses (accounting for about 80 % market share). Epoxy oligomers and/or monomers must be transformed to a highly crosslinked network macromolecule in the presence of a suitable curing agent under optimal conditions. A large variety of curing agents combined with many different kinds of epoxy resins results in a huge number of the epoxy formulations for specific applicatio
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