Predicting the Curing Time of Thermosetting Materials Using Differential Scanning Calorimetry
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icting the Curing Time of Thermosetting Materials Using Differential Scanning Calorimetry A. V. Khabenkoa, *, O. V. Tomchania, S. M. Ivanovaa, and M. N. Kordoa aRomashin
Corp. “Technology,” Obninsk, Kaluga oblast, 249031 Russia *e-mail: [email protected]
Received June 11, 2019; revised August 28, 2019; accepted October 31, 2019
Abstract—In this work, predictions of the curing time at a given temperature to a given degree of curing for four thermosetting materials have been made based on the data of differential scanning calorimetry (DSC) and they have been verified. An assessment of the possibility of using various methods for predicting the parameters of the reaction of thermosetting plastics has been given. Keywords: curing time, differential scanning calorimetry, model-less kinetics, Thermokinetics 3, thermosetting materials DOI: 10.1134/S1995421220040097
INTRODUCTION Determination of the curing time of a thermosetting material to a required degree at a given temperature provides very useful information, both for process engineers to adjust molding modes and for material developers to select the optimal composition of a material and its curing mode. Recently, several studies have reported kinetic parameters of the curing reactions of thermosetting materials based on the results of differential scanning calorimetry (DSC) tests [1–6], in which the data and the curing times were predicted for given very complex curing modes. However, there are no works in which predictions of the isothermal curing time are verified by determining the degree of conversion achieved at a given temperature for the time obtained in the modeling. In work [2], such a comparison was made for one epoxy composition and three degrees of conversion from 60 to 98%. This paper presents experimental data on verification of such predictions of conversion in four thermosetting materials with different compositions for five degrees from 10 to 100%. EXPERIMENTAL The following thermosetting materials were used in this study: –ENFB epoxy phenol binder, technical conditions TU 1-596-36–2005; –VEK-7 high-temperature epoxy compound, TU 1-596-475–2015; –VK-36R film epoxy adhesive, TU 1-596-389–96; and
–BMI-3 bismaleimide binder, TU 1-596-489– 2012. The curing time was predicted by two methods. (1) The model-less kinetic method (MKM) [7]. This method is based on the recording of DSC curves using a DSC-500 differential scanning calorimeter (Russia) in an air atmosphere at a heating rate of 5, 10, or 20°/min. The mass of the samples was 10–30 mg. The curves obtained were processed using the Ozawa– Flynn–Wall method of equal conversions to determine effective activation energy Ea of the curing reaction for degrees of curing from 5 to 100% with a 5% step. Using the obtained values of Ea and assuming that the reaction rate at the same degree of conversion is only a function of temperature, the time of curing of the materials under study to a given degree of curing was predicted without taking into account the kinetic model of the reaction using the equat
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