Effects of uniaxial tensile strain on the release of small molecules from silicone rubber

Abstract

Silicone rubber materials may be subject to mechanical strains which can affect the transport properties of small molecules loaded in the materials such as plasticizers and active molecules, hence deteriorating their intended mechanical properties or affecting their performance as carriers of active molecules. Therefore, it is important to understand the effects of mechanical strains on transport of small molecules in the silicone rubber matrix. In this work, silicone rubber sheets loaded with 2 wt% triacetin were stretched and held at four different lengths up to 125% engineering strain. The mass transfer coefficients and diffusion coefficients of triacetin in the strained silicone rubber were determined by monitoring the release of triacetin using headspace gas chromatography–mass spectrometry. It was found that there was no significant change of diffusion coefficient as the applied strain increased, which might result from two microstructure changes that had conflicting effects on diffusion: chain orientation and free volume deformation.

Effects of molecular interactions on the release of small molecules from silicone rubber

“…The diffusion coefficient was determined by fitting the experimental normalized release over time using Equation () in MATLAB 36 …”

“…The diffusion coefficient was determined by fitting the experimental normalized release over time using Equation (4) in MATLAB. 36 2.4 | Fourier-transform infrared (FTIR) spectroscopy analysis of samples loaded with OCT Neat sample and samples loaded with 1, 3 and 5 wt% OCT; 1 and 5 wt% OA; 1 and 5 wt% OB were analyzed using attenuated total reflection (ATR) FTIR spectroscopy to characterize possible interactions between small molecules and the rubber matrix. The instrument used was a Nicolet Magna-IR 550 spectrometer (Madison, WI) equipped with a Thermo Spectra Tech Foundation Series ATR module with a diamond crystal (Shelton, CT) DTGS KBr detector and KBr beam splitter (Thermo Electron Scientific Instruments LLC, Madison, WI).…”