Kinetics of Polymerization of Dimer Fatty Acids with Ethylenediamine Javad Heidarian, Nayef Mohd Ghasem, Wan Mohd Ashri Wan Daud Department of Chemical Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia Received 18 July 2003; accepted 30 September 2003 ABSTRACT: A generally applicable stoichiometric and ki- netic model was developed for the polymerization of dimer fatty acids with ethylenediamine. The rate equations were second-order before 90% conversion and were used between 405 and 475 K. The parameters of the rate equations were determined with nonlinear regression analysis. A compari- son of the model predictions and the experimental data showed that the approach was useful in predicting the po- lymerization kinetics. The equilibrium constant changed from 3.175 to 7.311. The frequency factor and activation energy for the forward rate constant before 90% conversion were 2,716,894 kg mol -1 min -1 and 66.7 kJ mol -1 , respec- tively. The equilibrium constant was independent of the temperature at frequency factor and activation energy val- ues of 74.4 and 9.7 kJ mol -1 , respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2504 –2513, 2004 Key words: polyamides; kinetics (polym.); modeling INTRODUCTION Dimer fatty acids have traditionally been used to syn- thesize and formulate hot-melt adhesives, flexo- graphic inks, functional coatings, and other engineer- ing materials. 1 Equation (1) shows the polymerization reaction be- tween dimer fatty acids and ethylenediamine: nH 2 NCH 2 CH 2 NH 2 + nHOOCC 34 COOH ^ HNHCH 2 CH 2 NHCOC 34 CO n OH + n - 1H 2 O (1) In industry, the water produced during the reaction should be purged to minimize the reverse reaction. The evaporation of ethylenediamine during the reac- tion is another important factor that needs to be con- sidered because if the evaporation becomes high, the loss of ethylenediamine will cause an imbalance be- tween the acid and amine values, and this will affect the final product. To obtain the reverse rate constant and the amount of evaporation with the temperature and time, we need an appropriate model. Most of the publications on fatty polyamide prepa- ration are patents, and no substantial work has been reported on the modeling of the kinetics of this reac- tion, except for products such as nylon 6 and nylon 66. 2 Vijay et al. 3 studied the kinetics of the reaction between ethylenediamine and dimeric fatty acids in the melt phase in the temperature range of 399 – 465 K and found that the reaction was second-order with an activation energy of 76.44 kJ mol -1 for conversions of up to 90%. For higher conversions, the reaction was third-order overall with an activation energy of 68.88 kJ mol -1 . In another work, Vijay et al. 4 carried out a kinetic study on the reaction between C 36 dimer acids and di- ethylenetriamine and triethylenetetramine in the tem- perature range of 420 – 465 K and found that the reac- tions overall followed second-order kinetics and had activation energies of 60.8 and 51.7 kJ mol -1 , respec- tively. These polyamides are known as reactive poly- amides because they can be crosslinked with other resins such as epoxy resins and they are not linear. Sumathi et al. 5 conducted kinetic studies on the reaction between ethylenediamine and C 36 dimeric fatty acids with benzyl alcohol as a solvent. The reac- tion was performed at temperatures between 435 and 465 K, and the kinetics were determined from the change in the acid value. The reaction was found to be third-order overall and had an activation energy of 128.9 kJ mol -1 . For reverse reaction and equilibrium constants, there are no published literature values available. In the aforementioned publication, nitrogen bubbling inside the reaction mass was applied to re- move the water produced, and so the reaction could be considered irreversible. In this work, the kinetics of the polyamidation re- action of ethylenediamine and dimer fatty acid are modeled with MATLAB, EXCEL, and EASY-FIT soft- ware, and the generated results are compared with the experimental data obtained. The reverse reaction and evaporation of water and amine are also examined. Correspondence to: W. M. A. W. Daud (ashri@um.edu.my). Contract grant sponsor: Malaysian Technical Corporation Program. Journal of Applied Polymer Science, Vol. 92, 2504 –2513 (2004) © 2004 Wiley Periodicals, Inc.