Kinetic Monte Carlo simulation of the photodegradation process of polyester-urethane coatings

Abstract

A numerical method to simulate reactions in a cross-linked polymer is developed and applied to the photodegradation process of polyester-urethane clearcoats during artificial exposure in a Weather-Ometer. This coarse-grained simulation method, which is based on a kinetic Monte Carlo scheme, is verified with experimental data on the depth-resolved changes in optical properties and chemical composition that have been previously determined. By modelling the depth-dependency of physical processes that occur in the coating, such as the absorption of photons and the diffusion of oxygen, the experimentally observed evolution of depth gradients in chemical composition can be well described by the simulation. A sensitivity analysis of individual simulation input parameters with respect to a set of resulting observables is performed and the results provide insight into the influence of specific reaction mechanisms on the overall degradation process and help to distinguish essential from less important processes. The values of input parameters that result in the most accurate simulation of the experimental data are determined with an optimisation procedure. In this way, the numerical values of several kinetic and physical parameters that are difficult to determine directly in an experimental way, such as various reaction rate constants, can be obtained from the simulations.

A Review of Multiscale Computational Methods in Polymeric Materials

“…The extension of the MC predictions to the simulation of microstructure evolution was first promoted by the incorporation of Ising lattice model in Potts-type MC models [68,69,70]. In the sense of using an internal kinetic measure such as the number of MC steps, this class of MC models is often referred to as kinetic MC models [71,72,73,74,75].…”

“…MC simulations have been utilized to describe a variety of phenomena in polymeric materials. Its application covers a wide range of problems including study of polymer degradation [71,73], development of surface morphology in thin films [76,77,78,79,80], heterophase interfaces [81,82,83,84,85,86,87,88,89,90,91,92,93,94], crystal growth and melting [95,96,97,98], morphology evolution [99,100,101,102,103,104,105,106], fracture behavior [107], diffusion [108,109,110,111], study of polymer melt viscoelasticity by nonequilibrium MC [112,113], and prediction of phase diagrams [114,115].…”

Modeling the reaction event history and microstructure of individual macrospecies in postpolymerization modification

“…Importantly, in this work, an advanced treatment for the description of hydrogen abstraction was additionally implemented in Module A, in agreement with the deterministic model of Giudici 35 and Hern andez-Ortiz and Vivaldo-Lima, 30 and the MC weight-based random sampling work of Tobita 55-57 and Zhao et al 58 For the mathematical description of hydrogen abstraction for macrospecies by means of kMC simulations, different approaches have also been proposed. For example, for the case of photodegradation of polyesterurethane coatings, Adema et al 59 applied a methodology including a weight factor to account for the number of hydrogen atoms that can be abstracted from the aliphatic reactant. For the poly(styrene peroxide) pyrolysis, the group of Broadbelt 60 used a matrix structure to characterize each macromolecule according to the number of functional groups.…”

Connecting polymer synthesis and chemical recycling on a chain-by-chain basis: a unified matrix-based kinetic Monte Carlo strategy

“…Some efforts include lattice based models which represent the polymeric material in a 2/3D matrix, where each node corresponds to a piece of the 3D polymer material. [62][63][64][65][66] A recent study by Adema et al 66 discusses the photodegradation of polyester-urethane coatings, where the coatings are subdivided into small cubes. These cubes are an ensemble of different chemical moieties and the degradation of some of these moieties is modeled using an elementary reaction scheme.…”