Cracking in UV-irradiated poly(methyl methacrylate)/functionalized graphene composites: solvent effect

Abstract

In this work, we study the combinational effects of UV irradiation, functionalized graphene (FG) sheets, and organic solvents on the crack evolution in PMMA/FG composites. The UV irradiation leads to the scission of polymer chains in the PMMA/FG composites with the FG sheets hindering the scission of polymer chains. The evolutions of surface cracks and the pre-formed crack in the PMMA/FG composites depend on the diffusion of organic solvents. The increase of Hansen solubility distance (HSD) with the solvent follows the order of cyclohexanol, 2EA, and 1-butanol sequence. The solvent with a smaller HSD diffuses faster in polymer, producing larger tensile stress to cause the nucleation and growth of cracks. The density of surface cracks and the length of the pre-formed crack decrease with increasing the FG fraction and HSD and increase with increasing the UV dose. The activation energy and heat of mixing for the growth of surface cracks increase with the FG fraction and HSD and decrease with increasing the UV dose. The activation energy for the growth of the pre-formed crack increases with increasing the FG fraction and HSD and decreases with increasing the UV dose. The activation energy for the inculcation period of the growth of the pre-formed crack has an opposite trend to the activation energy for the growth of the pre-formed crack versus the FG fraction, HSD, and UV dose. The experimental results show that the evolutions of surface cracks and the pre-formed crack follow the scaling law describing the diffusion of organic solvents in solids.