Computational modelling of the complex dynamics of chemically blown polyurethane foam

Abstract

This study presents computational analysis of the complex dynamics observed in chemically blown polyurethane foams during reaction injection molding process. The mathematical formulation introduces an experimentally motivated non-divergence free setup for the continuity equations which reflects the self expanding behaviour observed in the physical system. The foam growth phenomena which is normally initiated by adequate pre-mixing of necessary reactant polymers, leading to an exothermic polymerization reaction, bubble nucleation, and gas formation, is captured numerically. We assume the dependence of material viscosity on the degree of cure/polymerization, gas volume fraction, and temperature as well as nondependence of mixture density on pressure. The set of unsteady nonlinear coupled partial differential equations describing the dynamics of the system are solved numerically for state variables using finite volume techniques such that the front of the flow is tracked w ith high resolution interface capturing schemes. Graphical representation of the foam volume fraction, evolution of foam heights, and temperature distributions is presented. Results from our simulations are validated with experimental data. These results show good quantitative agreement with observations from experiments

Numerical Studies of the Viscosity of Reacting Polyurethane Foam with Experimental Validation

“…This approach is valuable for foam manufacturers who purchase PUR foam formulations from suppliers that do not provide the exact chemical composition. Computational studies of the authors of this paper about this are presented in [22]. A coupled system of partial differential equations for governing the foam expansion process based on Navier-Stokes equations including equations for heat transfer and degree of polymerization in the system was introduced there.…”

“…The simulation results were validated with experiments in tubes. The model described in [22] has also been successfully used to simulate the structural reaction injection moulding (SRIM) with spacer fabrics as inserts [23]. A further extension of the model was carried out in [24] to account for non-uniformity in the expansion of the foaming mixture.…”

“…The balance between gas creation, heat generation, bubble nucleation and growth as well as phase transition because of the polymerization in PUR foam formation suggests additional contribution of the gas fraction to the mathematical framework of the existing viscosity model [22,24]. Therefore, this study seeks to numerically investigate the influence of the gas volume fraction on the rheology of reacting PUR foams with the aim to validate and improve the existing material models.…”

Continuous, Free‐Formable Sandwich Design with 3D Fiber Reinforced Core for Increased Lightweight Level of Applications in Large‐Scale Production

“…The corresponding process flow contains many individual steps, each of which places individual demands on the tool design and has complex process parameters. Extensive preliminary investigations and process simulations within the individual process steps are necessary to avoid the misconception of a corresponding tool system with high investment costs of approximately 100.000 €. This paper describes the practical development work and studies carried out for this purpose.…”

Material Selection and Process Configuration for Free-Form, Voluminous and Textile-Based Multi-Material-Design by the Example of a Bucket Seat

“…The surface shells, the reinforcing spacer fabrics and the cushioning spacer fabrics are integrally implemented through adhesion and micro fitting. The expanding chemical foam reaction was simulated and validated parallel to these experiments [12]. The usage of textile-based organic shells, lightweight spacer fabrics and a high fluidity allows a free design while achieving high mechanical properties in the components.…”