Silicon adhesives vs. acrylic adhesives

Silicone and acrylic adhesives are those adhesives most commonly used in polyimide tapes. Polyimide adhesive tapes consist of two layers:

• the polyimide film and
• the adhesive that is applied to this film.

Although silicone adhesives are most commonly used for the adhesive layer, many applications require the tape to have an acrylic adhesive. The only way to understand why this is so is to compare the two types of adhesives – silicone and acrylic.

Silicone adhesives – the properties

Silicone offers better elongation at break. It is used for electrical insulation of electrical equipment. Since it offers the highest heat resistance among adhesives, it is also widely used for high-temperature insulation. Some of the properties of silicone adhesive tapes are listed below for better understanding:

• Silicone is highly flexible at temperatures below ambient.
• It can provide consistent performance over wide temperature ranges.
• It has very good aging and UV resistance.
• It can withstand high temperatures.
• Silicone also shows good resistance to polar solvents.

Acrylic adhesives – the properties

There are two types of acrylic adhesives:

• water-based and
• solvent-based.

Water-based acrylic adhesives dry more slowly compared to solvent-based adhesives. However, solvent-based acrylic adhesives usually have better resistance to other solvents, chemicals and water. Some of the properties of acrylic adhesives are as follows:

• Acrylic adhesives have adequate adhesion to a wide range of substrates.
• It has good aging, transmission and UV resistance, which are suitable for fiber optic applications.
• It also has reasonable temperature resistance, but is not as good as silicone adhesives.
• It has lower tack, which means it will stick less after drying.

Silicone vs. acrylic adhesives

Now that we know the properties of silicone and acrylic adhesives, we can move on to comparing the two types of adhesives.

Silicone adhesives can withstand a higher temperature range compared to acrylic adhesives. Acrylic adhesives have the property of being more brittle and therefore can break even at extremely low temperatures. Generally speaking, acrylic adhesives adhere better at medium temperatures, i.e., in a temperature range between 0°C and 100°C. On the other hand, silicone adhesives have higher adhesion at lower temperatures, i.e., below 0°C, as well as at higher temperatures, i.e., above 100°C.

So it seems that silicone adhesives are rather standard and preferred for most applications. However, in some situations where silicone cannot be used, acrylic adhesives must be used. As for the point of lower tack with pure acrylics, again, there is an alternative for better performance. Modified acrylic or rubber adhesives can be used for better tack. Pure acrylic adhesives are commonly used for tapes used for bonding, sealing or surface protection.

 

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