Swelling of Carbon Nano-Filler Modified Polydimethylsiloxane

Abstract

Polymers may absorb fluids from their surroundings via the natural phenomenon of swelling. Dimensional changes due to swelling can affect the function of polymer components, such as in the case of O-ring seals and microfluidic components. An understanding of the swelling behaviour and means for controlling it can improve the design of polymer components, for example, for the previously mentioned applications. Carbon-based fillers have risen in popularity to be used for the property enhancement of resulting polymer composites. The present investigation focused on the effects of three carbon-based nano-fillers (graphene nano-platelets, carbon black, and graphene nano-scrolls) on the dimensional changes of polydimethylsiloxane composites due to swelling when immersed in certain organic solvents. The study also assessed the mechanical and physical properties of the respective polymer composites. The primary experimental technique for this study is comprised of optical measurements in conjunction with digital image analysis to assess swelling dimensional changes of the prepared composites. Other experimental characterization techniques included polymer cross-linking density and electrical resistance measurements, electron and helium ion microscopy, X-ray diffraction and mechanical testing. The study showed that the extent and rate of swelling depended on the organic solvent in which the composites were immersed in. The investigation also revealed that the type of nano-fillers had no correlation to the degree of swelling; however, the addition of any carbon-based nano-filler increased the overall swelling. The experimental results led to the postulate that the increase of swelling was primarily caused by filler agglomeration.