Chemical Engineering Journal 152 (2009) 556–565 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Model-free kinetic analysis of melamine–formaldehyde resin cure A. Kandelbauer a,∗ , G. Wuzella b , A. Mahendran b , I. Taudes b , P. Widsten b a Department of Wood Science and Technology, University of Natural Resources and Applied Life Sciences, Peter Jordan Strasse 82, A-1190 Vienna, Austria b WOOD Carinthian Competence Centre, Kompetenzzentrum Holz GmbH, Klagenfurterstrasse 87 – 89, A-9300 St. Veit an der Glan, Austria article info Article history: Received 15 December 2008 Received in revised form 12 May 2009 Accepted 18 May 2009 Keywords: Melamine–formaldehyde resin Kinetics Isoconversional kinetics Curing Differential scanning calorimetry abstract The curing behaviour of an industrial melamine–formaldehyde (MF) resin with four different commercial curing catalysts was analyzed from thermal studies using differential scanning calorimetry (DSC) and model-free kinetic (MFK) analysis. For the kinetic study, the mathematical approaches developed by Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and Vyazovkin were used to calculate curing isotherms. With all kinetic approaches the apparent activation energy, E a , depended to some extent on the degree of conversion (˛). Besides being obscured by experimental errors, in some cases higher E a (˛) were calculated with higher catalyst concentrations, illustrating that E a (˛) may not be the only relevant parameter to compare different resin systems. However, E a (˛) was found to be well suited for predicting the isothermal curing behaviour of MF resin. The time required for achieving a certain conversion, ˛, was calculated for different temperatures. By comparing the calculated isotherms to experimental isothermal data obtained at 80, 100, and 120 ◦ C it was found that the Vyazovkin approach in its advanced form was best suited to predict the curing kinetics of MF with all catalyst systems tested. By applying DSC–MFK it was possible to detect and characterize the de-blocking behaviour of different catalysts for MF curing. The presented results illustrate that isoconversional methods for kinetic analysis of thermochemical data can be applied to the investigation and optimization of melamine–formaldehyde resins. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Products containing melamine-based aminoplastic resins are present in our daily environment, for example, as furniture, flooring, or exterior cladding, and represent an important market segment. Approximately 1 million metric tons of melamine was consumed in 2006; for 2009, the consumption is estimated to reach 1.3 million tons [1]. The major consumers of melamine are the wood-based panel and laminate manufacturers, which supply the furniture and construction industries with high-quality surface-coated interior and exterior materials [1]. Typically, particleboards are manufac- tured by gluing comminuted lignocellulosic material with 20–25% (w/w) of a melamine–formaldehyde (MF) resin in a hot press [2]. Practically all of these boards are subsequently coated with sheets of decorative paper that are impregnated with MF resins to obtain wood-like or custom design surfaces [3]. While about 30% of the melamine produced in 2006 was consumed in the manufacture of wood adhesives, the largest proportion was used for MF impreg- nation and coating resins for industrial laminates (ca. 50%). The remainder went to surface coatings (9%), moulding compounds (7%), and other applications [1]. ∗ Corresponding author. Tel.: +43 4212 494 8002; fax: +43 4212 494 8099. E-mail address: andreas.kandelbauer@boku.ac.at (A. Kandelbauer). The curing behaviour of an MF resin and its degree of cross- linking govern the customized product properties. If the resin is not sufficiently cured, particleboards glued with MF will lack mechan- ical strength [4] and surface finishes based on MF-impregnated papers will lack hardness, durability, brilliance, and resistance towards hydrolysis and chemical agents [5]. The cost of particle- board manufacturing is mainly governed by the production line speed so that the reaction time required for a specific cross-linking degree of MF is an important issue. Lamination of impregnated sheets onto wood-based panels takes place in presses at temper- atures between 160 and 180 ◦ C. Depending on the type of product, the pressurized cycle times of modern press equipment range from 6 to 30s for short-cycle presses to several minutes in multi-platen presses. The supplier of impregnated paper must be able to deliver products suitable for the whole variety of different pressing con- ditions used by his customers. In short, for the whole range of products in the wood-based panel industry, a rapid achievement of an optimal cross-linking degree upon pressing is desired and resin technologists need to know how to design gluing formulations and impregnation solutions complying with product properties, pro- duction technology, and production speed. A key issue in tailoring the curing behaviour of MF resins is the right choice of type and amount of curing catalyst [6]. To obtain the desired product properties in the shortest time possible, it must be known what degree of cross-linking (˛) can be obtained with a 1385-8947/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2009.05.027