~Which squeegee to choose (from ink solvent)~
One of the most frequently asked questions about squeegees is about solvents.
For example, "What kind of squeegee can be used with the solvent XX that is used as the ink diluent?", "What is the appropriate cleaning agent for cleaning the squeegee?" The squeegee swells up quickly. Do you have any other good squeegees?"
For example, "What kind of squeegee can be used with the solvent XX that is used as the ink diluent?", "What is the appropriate cleaning agent for cleaning the squeegee?" The squeegee swells up quickly. Do you have any other good squeegees?"
In order to explain the solvent resistance of squeegees, it is first necessary to confirm various properties of ink solvents.
Solvents have different colors and odors, but they are in liquid form. Among them, the "polarity" of the solvent greatly affects the solvent resistance of the squeegee. What does this "polarity" mean?
Solvents have different colors and odors, but they are in liquid form. Among them, the "polarity" of the solvent greatly affects the solvent resistance of the squeegee. What does this "polarity" mean?
"Polarity" is the electrical bias within a molecule. Solvents used in ink that have a large electrical bias are called "polar solvents," while solvents that have a small electrical bias are called "non-polar solvents."
Typical polar solvents are water and alcohol. A typical non-polar solvent is a thinner solvent such as toluene.
Typical polar solvents are water and alcohol. A typical non-polar solvent is a thinner solvent such as toluene.
By the way, let me digress a little, but the bad relationship is called "the relationship between water and oil." It is a way of saying that water and oil that do not dissolve in each other are likened to human relationships. In chemistry, substances with similar properties mix with each other. In the case of water and oil, water, which is a polar solvent, and oil, which is a non-polar solvent, do not mix because their electrical properties are too different. (Since polar solvents mix easily with water, they are sometimes called hydrophilic solvents.)
This happens not only between liquids such as solvents, but also between liquids and solids. If the resin and solvent both have the same polarity, they will try to mix with each other. This will cause the resin to swell.
Back to the squeegee story.
The material commonly used for squeegees is "ester urethane rubber". The material of the "E-Fine Squeegee" and "New Super Urethane Squeegee" that we sell is also "ester-based urethane rubber". Urethane rubber is a synthetic rubber characterized by excellent abrasion resistance, but the "urethane bond" that is the center of the chemical bond of urethane rubber has "polarity".
Most of the solvents used in screen printing inks are "non-polar", so they do not try to mix with "polar" resins such as urethane rubber, so urethane rubber does not swell. Therefore, if you use a urethane rubber squeegee for screen printing, problems will not occur in most cases.
However, there are some inks that use "polar solvents". In addition to water, polar solvents include DMF, THF, and γ-butyl lactone. Polar urethane rubber melts violently because polar materials melt well together. In other words, it swells.
The pictures below are of squeegees immersed in polar and non-polar solvents for 24 hours. As you can see, the squeegee swells violently in polar solvents.
The material commonly used for squeegees is "ester urethane rubber". The material of the "E-Fine Squeegee" and "New Super Urethane Squeegee" that we sell is also "ester-based urethane rubber". Urethane rubber is a synthetic rubber characterized by excellent abrasion resistance, but the "urethane bond" that is the center of the chemical bond of urethane rubber has "polarity".
Most of the solvents used in screen printing inks are "non-polar", so they do not try to mix with "polar" resins such as urethane rubber, so urethane rubber does not swell. Therefore, if you use a urethane rubber squeegee for screen printing, problems will not occur in most cases.
However, there are some inks that use "polar solvents". In addition to water, polar solvents include DMF, THF, and γ-butyl lactone. Polar urethane rubber melts violently because polar materials melt well together. In other words, it swells.
The pictures below are of squeegees immersed in polar and non-polar solvents for 24 hours. As you can see, the squeegee swells violently in polar solvents.
Urethane rubber cannot be used when printing ink containing polar solvents.
In this case, it is necessary to use non-polar rubber as the squeegee, which is the opposite of urethane rubber. In other words, if you use a non-polar rubber for a polar solvent like water and oil, they will not mix with each other and will not swell.
We sell PS squeegees that use non-polar propylene rubber.By using this squeegee, the squeegee will not swell even with ink containing polar solvents.
The photo below shows a PS squeegee immersed in a polar solvent for 24 hours. PS squeegees that use propylene rubber do not swell even in polar solvents.
In this case, it is necessary to use non-polar rubber as the squeegee, which is the opposite of urethane rubber. In other words, if you use a non-polar rubber for a polar solvent like water and oil, they will not mix with each other and will not swell.
We sell PS squeegees that use non-polar propylene rubber.By using this squeegee, the squeegee will not swell even with ink containing polar solvents.
The photo below shows a PS squeegee immersed in a polar solvent for 24 hours. PS squeegees that use propylene rubber do not swell even in polar solvents.
So what happens when you dip a "non-polar" PS squeegee into a "non-polar" solvent?
This time the squeegee swells because it is non-polar. The photo below shows a PS squeegee immersed in a non-polar solvent for 24 hours. Now you can see that the PS squeegee is swollen.
This time the squeegee swells because it is non-polar. The photo below shows a PS squeegee immersed in a non-polar solvent for 24 hours. Now you can see that the PS squeegee is swollen.
summary:
Solvents used in ink include polar solvents and non-polar solvents.
Most of the inks used in screen printing are non-polar, so using a urethane rubber squeegee is fine in most cases.
However, some inks use polar solvents. A urethane rubber squeegee cannot be used for this. In this case, it is better to use a PS squeegee made of propylene rubber.
Solvents used in ink include polar solvents and non-polar solvents.
Most of the inks used in screen printing are non-polar, so using a urethane rubber squeegee is fine in most cases.
However, some inks use polar solvents. A urethane rubber squeegee cannot be used for this. In this case, it is better to use a PS squeegee made of propylene rubber.
