What size holes can be filled using vacuum impregnation?
At Godfrey & Wing, we are often asked how large and how small of a pore may be sealed or how long it takes to fill porosity using vacuum impregnation. There are multiple variables that directly impact this answer including the relationship between sealant viscosity, pore size and pore depth.
We know that impregnation sealants flow easily through small pores since Godfrey & Wing sealants are routinely pumped through a 1 micron filter during the filling of containers.
The variables that impact flow and penetration of sealant into porosity are:
- Size of pore to be filled
- Depth of pore to be filled
- Viscosity at application temperature
- Percent of air removed from the pore
- Pressure applied to force sealant into pore
Flow calculations are based on the experiments of early 19th century French physician Poiseuille. Poiseuille observed that flow is proportional to the radius of the cylindrical tube raised to the 4th power. He also noticed that it is inversely proportional to the length of the tube and the liquid viscosity. This formulation was published in 1846 and is known as Poiseuille’s Law (PL).
Some considerations must be taken into account when applying PL such as porosity is not perfectly cylindrical, and the size of the porosity varies throughout the component. For more detailed information about the relationship between sealant viscosity, pore size and pore depth and Poiseuille’s Law, click here to download the complete whitepaper.