Learn More About Other Pressure-Sensitive Adhesives

Silicone Pressure-Sensitive Adhesives

Silicone pressure-sensitive adhesives are highly resistant to heat, weather, chemicals, and water. They are also resistant to cold, making them useful for many applications across a broad range of temperatures.

Features

Silicone pressure-sensitive adhesives comprise silicone polymers and silicone resins that serve as tackifiers.
Silicone polymers are not very adhesive, so they are mixed with silicone resins to make them stickier. The level of adhesion can be adjusted by changing the mix proportions of the polymers and resins or using different resins.
Silicone pressure-sensitive adhesives are known for being fluid and soft without being too sticky, and stick well to many different materials, including silicone rubber and fluororesins that typically do not take well to rubber and acrylic pressure-sensitive adhesives.
The mildly adhesive types used on protective films for electronic devices are excellent at releasing air, minimizing air bubble entrapment during application.
They can also be used across a broad range of temperatures (-60 to 250°C). They do not melt or harden or experience substantial changes in adhesive strength in high or low temperatures, meaning they can stick to materials even when heat is applied or temperatures are low. Silicone pressure-sensitive adhesives are ideal for medical tape because they do not stretch the skin or pull out hairs—they do not irritate the skin much when applied or hurt much when removed.
They are also resistant to water, weather, oils, chemicals, and electricity, and are waterproof. With these and other characteristics, silicone pressure-sensitive adhesives are versatile and useful for a broad range of applications.

Applications

Protective film, waterproof tape, anticorrosion tape, medical tape, heat-resistant tape, electrical tape, and more.

Advantages and Disadvantages of Silicone Pressure-Sensitive Adhesives

The advantages and disadvantages of silicone pressure-sensitive adhesives are as follows.

Advantages

• Easy to remove and reapply
  Silicone pressure-sensitive adhesives are very easy to remove and reapply without losing stickiness or adhesive strength.
• High durability
  Silicone pressure-sensitive adhesives are highly resistant not only to heat and cold, but also to ultraviolet rays, sunlight, and other elements of weather. Their physical properties essentially remain intact even in harsh climatic conditions, making them apt for use outdoors. They are used on anticorrosion tape applied to the parts of pipes exposed to the elements, pipe joints, and other areas to prevent metal corrosion.
• Resistant to solvents and chemicals
  Silicone pressure-sensitive adhesives resist infiltration by alcohol and other polar organic compounds. Although they swell on contact with non-polar or low-polarity compounds such as benzene and toluene, they return to normal when the solvents are removed. They are also highly resistant to oils in high temperatures (100°C or higher).

Disadvantages

• Expensive
  Silicone pressure-sensitive adhesives are more expensive than other types of adhesives.
• Weak adhesion
  Silicone pressure-sensitive adhesives typically have low adhesive strength, making them a poor choice in situations where strong adhesion is required.
• Possible adverse effects of siloxanes
  Gasified siloxanes pose a risk of product defects, including contact faults in electronic components and fogging in optical components. They can also contaminate surfaces when applied in high temperatures, for example the surfaces of wafers when used on semiconductor tape.

Acrylic pressure-sensitive adhesives are a better choice when strong adhesive strength is required, or to achieve balance between price and performance.

Urethane Pressure-Sensitive Adhesives

Urethane pressure-sensitive adhesives are mildly adhesive and very easy to remove and reapply. Urethane resins are versatile and useful for a broad range of applications, including as adhesives. Their characteristics make them a suitable base for pressure-sensitive adhesives. Although urethane compounds currently lack versatility as pressure-sensitive adhesives, work is underway to add new value and develop more applications.

Features

Urethane pressure-sensitive adhesives are composed of polyols and polyisocyanates and contain urethane groups. They comprise high-cohesion hard segments and low-cohesion soft segments that can be adjusted to elicit and control various physical properties, including adhesion and holding power. The constituent urethane groups are highly cohesive, making urethane pressure-sensitive adhesives mildly adhesive and easy to remove and reapply. Urethane pressure-sensitive adhesives are also being used as medical tape for the strength of their other characteristics. They are highly moisture-permeable thanks to high polarity, and their properties are stable due to elasticity that is largely independent of temperature and frequency. They also give off minimal odors and cause very little skin irritation.
However, urethane pressure-sensitive adhesives require creative steps to control their hardness and molecular weight, making it somewhat impractical to develop adhesive properties for a broad range of applications. Studies are underway to solve this problem through chain extension or by introducing plasticizers to expand design freedom and improve adhesive properties. Urethane pressure-sensitive adhesives have characteristics that their rubber and acrylic counterparts do not, so if these drawbacks are resolved, we may be able to create pressure-sensitive adhesives with new added value.

Applications

Protective film, medical tape, industrial protective tape, and more.

Advantages and Disadvantages of Urethane Pressure-Sensitive Adhesives

The advantages and disadvantages of urethane pressure-sensitive adhesives are as follows.

Advantages

• Easy to remove and reapply
  Urethane pressure-sensitive adhesives are easy to remove and reapply, and can be peeled off without leaving adhesive residue even if left on for long periods of time.
• Low dependence on external factors
  Urethane pressure-sensitive adhesives essentially maintain their adhesive strength regardless of temperature and peeling speed. Their hardness generally stays the same around room temperature, resulting in consistent adhesive strength.
• High moisture permeability
  Urethane pressure-sensitive adhesives are highly moisture-permeable, for example, allowing water vapor passage to reduce discomfort when applied to the skin.
• Conducive to high solid differentiation
  Urethane pressure-sensitive adhesives have a relatively low molecular weight, making it easy to increase the ratio of active ingredients.

Disadvantages

• Low adhesion and tack
  Urethane pressure-sensitive adhesives generally have low adhesive strength and tack, making them a poor choice in situations where strong adhesion or initial adhesion are required. Also, adjusting their cohesion and degree of crosslinking to augment their adhesion reduces the strength of the pressure-sensitive adhesive layer, which may result in adhesive residue.
• Will not stick to olefines
  Urethane pressure-sensitive adhesives often do not stick well to low-polarity materials.
• Difficult to increase molecular weight
  The molecular weight of urethane pressure-sensitive adhesives cannot be increased easily, making it difficult to increase or otherwise adjust the viscosity. Doing so may also compromise the durability of the pressure-sensitive adhesive.

Acrylic pressure-sensitive adhesives are a better choice when strong adhesive strength, tack, or durability are required.