Anisotropic swelling of elastomers filled with aligned 2D materials

Mufeng Liu,Suhao Li,Dimitrios G Papageorgiou,Robert J Young,Ian A Kinloch

doi:10.1088/2053-1583/ab6f7b

Mufeng Liu, Suhao Li + Show 3 more

Open Access

https://doi.org/10.1088/2053-1583/ab6f7b

Copy DOI

Abstract

A comprehensive study has been undertaken on the dimensional swelling of graphene-reinforced elastomers in liquids. Anisotropic swelling was observed for samples reinforced with graphene nanoplatelets (GNPs), induced by the in-plane orientation of the GNPs. Upon the addition of the GNPs, the diameter swelling ratio of the nanocomposites was significantly reduced, whereas the thickness swelling ratio increased and was even greater than that of the unfilled elastomers. The swelling phenomenon has been analyzed in terms of a modification of the Flory–Rehner theory. The newly-derived equations proposed herein, can accurately predict the dependence of dimensional swelling (diameter and thickness) on volume swelling, independent of the type of elastomer and solvent. The anisotropic swelling of the samples was also studied in combination with the evaluation of the tensile properties of the filled elastomers. A novel theory that enables the assessment of volume swelling for GNP-reinforced elastomers, based on the filler geometry and volume fraction has been developed. It was found that the swelling of rubber nanocomposites induces a biaxial constraint from the graphene flakes.

Highlights

Crosslinked rubbers swell when they come in contact with liquids
The actual weight fractions of the fillers in the different elastomers were confirmed by thermogravimetric analysis (TGA) and the volume fractions are listed in Table S4 (Supporting Information)
A number of elastomers were filled with different graphene nanoplatelets and carbon blacks to study the swelling behaviour of the nanocomposites in solvents

Summary

Introduction

Crosslinked rubbers swell when they come in contact with liquids. The swelling of rubbers impacts negatively their mechanical properties and makes the materials lose their serviceability. The theory proposed by Kraus has been shown to be applicable to carbon blacks and other types of spherical fillers [2,3,4]. The reduced swelling ratio of carbon black-reinforced elastomer composites as the result of an improved stiffness modulus is central to Kraus' theory [1]. The anisotropy of modulus leads to anisotropic swelling when the nanocomposites are immersed in liquids [5, 6]. In this case, Kraus' equation is not applicable, because the reinforcement from asymmetric fillers is no longer uniform and leads to complexity in the swelling process

Methods

Results

Conclusion