Abstract
Due to its simple curing and very good mechanical properties, Sylgard 184 belongs to the most widely and frequently used silicones in many industrial applications such as microfluidics and microengineering. On top of that its mechanical properties are further controllable through the curing temperature, which may vary from ambient temperature up to 200 °C; the lower the curing temperature the lower the mechanical properties (Johnston et al. in J Micromech Microeng 24:7, 2014. 10.1088/0960-1317/24/3/035017). However, certain specialised application may require even a softer binder than the low curing temperature allows for. In this study we show that this softening can be achieved with the addition of silicone oil into the Sylgard 184 system. To this end a series of Sylgard 184 samples with varying silicone oil concentrations were prepared and tested (tensile test, rotational rheometer) in order to determine how curing temperature and silicone oil content affect mechanical properties. Curing reaction of the polymer system was found to observe 2nd order kinetics in all cases, regardless the oil concentration used. The results suggest that within the tested concentration range the silicone oil addition can be used to soften commercial silicone Sylgard 184.
Highlights
Due to their simple fabrication, good transparency, chemical inertness, biocompatibility, and elasticity with decent mechanical properties, silicone elastomers, namely polydimethylsiloxane (PDMS), have quickly become indispensable in many applications
The effects of the oil addition and curing temperature used are studied in order to determine optimal settings, for which sufficient softening of Sylgard 184 takes place without occurrence of negative phenomena such separation of silicone oil from Sylgard 184 composition or considerable
We present an experimental study delving into the effect of curing temperature on final mechanical properties of Sylgard 184, a matrix widely used in industrial applications
Summary
Due to their simple fabrication, good transparency, chemical inertness, biocompatibility, and elasticity with decent mechanical properties, silicone elastomers, namely polydimethylsiloxane (PDMS), have quickly become indispensable in many applications They are used in stretchable wearable electronics1, biomedicine[2,3], microelectromechanical systems (MEMS)[4], microfluidic chips[5], in biomaterials for studying cell mechanobiology[6] and lately in the field of magnetorheology[7,8]. One needs to increase the distance between cross-links, which can be achieved, for instance, through using bottle-brush polymers[19], by choice of polymerization strategy[20], change of molecular weight[21], decreasing concentration of reactive groups[22], addition of p lasticizer[23], increasing dangling c hains[24] or changing crosslinker functionality[25] This can be in theory accomplished by changing the ratio between a prepolymer and a curing agent. We notice how this polymer system can be further “softened” by extension with silicone oil for the purpose of applications requiring highly elastic soft polymeric matrix/binder with simple method of preparation
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