Abstract
In this work, the characterisation of reaction kinetics of a methylene diphenyl diisocyanate (MDI)-based fast curing polyurethane resin (PUR) and the mathematical description of its curing process are presented. For the modelling of the reaction process isoconversional methods, which are also called model-free approaches, are used instead of model-based approaches. One of the main challenges is the characterisation of a reactive system with a short pot life, which already starts to crosslink below room temperature. The main focus is the evaluation of the applicability of isoconversional methods for predicting the reaction kinetics of fast curing polyurethane resins. In order to realise this, a repeatable methodology for the determination of time- and temperature-dependent reaction curves using differential scanning calorimetry (DSC) is defined. The cure models defined by this method serve as the basis for process simulations of PUR processing technologies such as resin transfer moulding (RTM) or reactive injection moulding (RIM) and reactive extrusion (REX). The characterisation of the reaction kinetics using DSC measurements is carried out under isothermal and non-isothermal conditions. Within this work isoconversional methods have been applied successfully to experimentally determined DSC data sets. It is shown that the reaction kinetics of fast curing polyurethane resins can be predicted using this methods. Furthermore, it is demonstrated that the time-dependent change of conversion of the considered polyurethane under isothermal curing conditions can also be predicted using isoconversional methods based on non-isothermal DSC measurements. This results in a significant reduction in the experimental effort required to characterise and model the curing process of polyurethanes.
Highlights
The processing of thermoset moulding materials like polyurethanes (PUR) is a very important field of plastics technology
The procedure isothermalabove measurement) and six different curing measurement) relation described for the preparation of the differential scanning calorimetry (DSC) temperatures samples and
The experimental data obtained were used for the mathematical description and successfully applied
Summary
The processing of thermoset moulding materials like polyurethanes (PUR) is a very important field of plastics technology. The various properties of this material, especially the wide range of mechanical properties, are apparent in various application areas like the automotive industry, the construction industry as well as in products for everyday domestic needs. The mechanical properties of polyurethanes, depending on their chemical structure, provide the entire spectrum of material behaviour of engineering plastics, from rubber-elastic to hard elastic brittle deformation behaviour. It can be assumed that due to the application-specific variable material properties the importance of polyurethanes in all areas of technical applications will increase. In order to meet the requirements of modern development processes, it is necessary to carry out specific research and further developments, especially in the area of numerical simulation of polyurethane manufacturing processes, the calculation of mechanical stresses in polyurethane components and the prediction of process specific component properties.
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