Kinetic Prediction of Fast Curing Polyurethane Resins by Model-Free Isoconversional Methods

Abstract

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.

Kinetic Analysis of the Thermal Degradation of Recycled Acrylonitrile-Butadiene-Styrene by non-Isothermal Thermogravimetry

“…Thus, these methods are habitually called Model-Free Kinetic methods (MFK). These methods are widely used to study the apparent activation energy of thermal activated processes (degradation and cross-linking) [23]. [∂ln(dαnormaldt)∂ T −1]αi= −Ea,αiR…”

Description of the Resin Curing Process—Formulation and Optimization

“…Due to many different resin systems used in practical applications, different RK models have been proposed so far [7,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]. Many RK models are based on the following formulations (including a combination of them):…”

“…Due to this fact, a proper selection of the RK model is an important practical issue. On the basis of the validation of the particular models to the experimental tests [27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57], the practical recommendations regarding the selection of the RK models for composite materials (Table 1) and fabrication processes of fiber composites (Table 2) are given.…”

“…Application of them allows for the determination of the optimal shape of a mold and the optimal process of heating and cooling of the mold and sample (a temperature-time history, a location of inlet gates and a location of heaters). Many different reaction kinetics (RK) models have been proposed so far [22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37]. In practical application, the most often used are models (or their extended or developed formulations) proposed by Kamal and Sourour [22] and Bogetti and Gillespie [23].…”

“…The above-mentioned models have been successfully applied to the different composite materials and resin systems such as carbon-fiber reinforced polymer (CFRP) [38,39,40,41,42,43,44], glass-fiber reinforced polymer (GFRP) [45,46,47,48], epoxy resin systems [49,50,51], fast cure epoxy [30,32,37]. The applicability of the curing models has been also confirmed for different manufacturing technologies of composite structures, such as: liquid silicone rubber (LSR) [52], resin film infusion (RFI) [53], resin transfer molding (RTM) [30,31,33,38,44,51,54], compression resin transfer molding (C-RTM) [32], reactive injection molding (RIM) [30], vacuum-assisted resin transfer molding (VARTM) [55,56], reactive extrusion (REX) [30], autoclaving [57] and out-of-autoclave (OOA) [34,37]. A detailed description is presented in Chapter 2.…”