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Properties of Penetrant Materials (Viscosity (Fluid's resistance to…
Properties of Penetrant Materials
Density/ Specific gravity
has little effect on the performance
Force = πr2hpg
Viscosity
Fluid's resistance to flow
Affect the speed of the penetrant enter the defects
Higher viscosity, higher resistance to the flow, speed of the flow will decrease
Ultraviolet and Thermal Stability of Penetrant Indications
will have negative effect if intense UV light and elevated temperature
High UV
fluorescent materials will lose brightness
high Temp
penetrants experience heat degradation
Surface Energy
energy required to form a unit of area of new surface at the interface
To spread over the material, the penetrant must have high adhesive force and low cohesive force in order for wetting to occur
If adhesive force higher than cohesive force, wetting occurs
Capillarity
driving force that draws penetrant into narrow openings
Force = 2 πrσ LG cosq
Capillary Pressure = (2 σLG cos Θ)/ r