Effect of varying mixing ratio of PDMS on the consistency of the soft-contact Stribeck curve for glycerol solutions

• Friction curves for glycerol solutions were measured using different PDMS specimens.
• Master Stribeck curve for glycerol solutions was generated using the specimens.
• Variability in the consistency of friction curves is present between specimens.
• This finding calls on field-standard materials/synthesis protocols for consistent data interpretation.

We study how varying the mixing ratio of base and curing agent for polydimethylsiloxane (PDMS) affect the consistency of tribological data using a newly developed soft-contact ball-on-three-plate tribocell. The mixing ratio is systematically varied and the resultant surfaces are characterized for Young׳s modulus, surface chemistry, and surface roughness with texture analyzer, Fourier transform infrared spectroscopy (FT-IR), and atomic force microscopy (AFM). We find, from both friction curves for a single glycerol solution and master Stribeck curves for a series of glycerol solutions, that the PDMS surface properties are highly sensitive to numerous variables put into the synthesis protocol and may affect the consistency of tribological responses. Our observations suggest a necessity for field-standard materials/synthesis protocols for general soft-contact tribological characterization.