Modelling effects of moisture on mechanical properties of crosslinked polyurethane adhesives

TL;DR

This paper develops a coupled micromechanical and diffusion model to analyze how moisture affects the mechanical properties and aging of crosslinked polyurethane adhesives, accounting for their viscoelastic and hygroscopic behavior.

Contribution

It introduces a novel coupled modeling approach combining micromechanical network and Langmuir diffusion models for moisture-induced aging analysis.

Findings

Moisture causes exponential decay in mechanical properties.

The model predicts material softening due to chain breakage.

Coupled model effectively simulates aging process under moisture exposure.

Abstract

Crosslinked polyurethane adhesives show large deformation viscoelastic behaviour and age under the moisture influence because of their hygroscopic behaviour. The viscoelastic behaviour of the material is modelled with the micromechanical network model. The micromechanical model considers the shorter and longer chains with a probability distribution function. The network evolution concept is used to model softening of material due to the breakage of the shorter chains with an increase in deformation. The moisture diffusion in the polyurethane adhesive is behaviour, therefore Langmuir-type diffusion model is used to model moisture diffusion. The transported moisture in the material leads to an exponential decay in the mechanical properties causing the ageing of the material. The micromechanical model needs to be coupled with the Langmuir-type diffusion model to analyse the ageing process, where the mechanical properties are considered as the function of the local moisture concentration.