Compatibility of poly(dimethylsiloxane) microfluidic systems with high viscosity hydrocarbons

In this work, the compatibility of poly(dimethylsiloxane) (PDMS) with high viscosity petroleum liquids (bitumen) was evaluated to study the possibility of using PDMS microchannels in heavy oil and bitumen extraction research using solvent based methods such as Vapor Extraction. Three curing agent to base ratios (1:2, 1:10, and 1:20) were used to fabricate PDMS. Swelling ratio of these three samples in the vicinity of different organic solvents and diluted bitumen were evaluated by measuring the weight of sample every 15 min. It was found that 1:10 ratio PDMS was preferential ratio for minimizing absorption. We were particularly interested in the kinetic of swelling, deformation, and discoloration of PDMS. The hypothesis was that a PDMS microchip can still be used for experiments with heavy oil and bitumen if the experiment time is much shorter than the time it takes for PDMS discoloration, swelling, and deformation. The coating of PDMS slabs with trichloro (1 h 1 h 2 h 2 h-perfluorooctyl) silane was also tested and swelling ratios were again measured to evaluate the effect of surface coating. Swelling ratios were at the same order for uncoated PDMS which shows silane coating is not able to improve the solvent compatibility of PDMS. Moreover, solubility parameter was used to predict the swelling ratio of 1:10 PDMS sample in organic solvents. It predicts that hexane and toluene have the highest solubility that was in great agreement with experimental results. It seems that solubility parameter is a reliable factor to qualitatively predict the swelling ratio of PDMS. The effect of bitumen on transparency of PDMS was also studied using Ultraviolet–Visible spectrophotometer.