Characterisation and FE Modelling of the Sorption and Swelling Behaviour of Polyamide 6 in Water.

Anna Katharina Sambale,Markus Stommel,Michael Stanko,Jessica Emde

doi:10.3390/polym13091480

Anna Katharina Sambale, Markus Stommel + Show 2 more

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https://doi.org/10.3390/polym13091480

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Abstract

Polyamide 6 (PA6) is known to absorb water from its environment due to its chemical structure. This water absorption leads to a change in the mechanical properties as well as an increase in volume (swelling) of the polyamide. In the present work, the sorption and swelling behaviour of polyamide 6 in different conditioning environments was experimentally investigated on different part geometries to develop a finite element (FE) method on the basis of the measured data that numerically calculates the sorption and swelling behaviour. The developed method includes two analyses using the Abaqus software. Both the concentration-dependent implementation of the simulation parameters and the calculation of swelling-induced stresses are performed. This enables the modelling of the sorption curves until maximum saturation is reached and the simulation of the characteristic S-shaped swelling curves. Therefore, the developed methodology represents an efficient method for predicting the sorption and swelling behaviour of polyamide 6 parts during conditioning in a water bath. The determined properties provide the basis for the development of an FE-based simulation environment to take moisture absorption into account during the part design. This enables the calculation of moisture-induced swelling processes and the resulting initial stresses in a given part.

Highlights

Polyamide 6 (PA6) is able to absorb moisture from the surrounding air and release it again until it is in balance with the environment
To ensure that the influence of different part wall thicknesses was considered for determining the sorption and swelling behaviour, a simple, step-shaped sample geometry was developed
This geometry has the advantage that it represents a part with different wall thicknesses, which can be separated at the steps into individual bar-shaped parts

Summary

Introduction

The water molecules can be bound by hydrogen bonds between the amides and increase the chain segment mobility due to the increased molecular chain spacing [2,3] This lowers the glass transition temperature of the material from about 60 ◦ C for dry PA6 to about −20 ◦ C for completely water-saturated material [4,5,6,7,8,9]. To ensure that the influence of different part wall thicknesses was considered for determining the sorption and swelling behaviour, a simple, step-shaped sample geometry was developed. This geometry has the advantage that it represents a part with different wall thicknesses, which can be separated at the steps into individual bar-shaped parts. Conclusions can be drawn about the interaction of the individual part areas

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