Silicone adhesive is among the most common and widely used silicone applications in numerous industries. In this blog, we will learn about silicone adhesive and its various types .
What is silicone adhesive?
Silicone adhesive, whose primary ingredient is silica, is a water-resistant polymer. Silica is derived from silicon and is commonly found in the form of sand in quartz. Silicone is an artificial synthetic compound derived from silicon with organic compounds.
Silicone adhesives have a wide range of applications and the silicone adhesive type will depend on the industry you are working with/in. They act as non-toxic alternatives to the toxic adhesives, offering a safe method for securing and attaching surfaces.
Silicone adhesives form a strong long-lasting bond on any surface, due to their excellent chemical stability and resistance to weather and moisture. They are used in the medical field to create a tight seal over the skin and prevent any further infections, as silicone adhesive is biocompatible.
Steps of making silicone adhesive
The primary element of silicone adhesive is silica. It can be found in the form of glass, quartz, emerald, or glass. Silica, also known as silicon dioxide, is a combination of silicon and oxygen. There are three steps involved in the making of silicone adhesive:
Step 1: Isolating silica from silicon
This step involves isolating the silica from the silicon to manufacture silicone as an adhesive. In the first step of producing silicone adhesive, silicon is isolated from silica. When a large amount of quartz is heated up to 1800 degrees Celsius, pure silicon is obtained. After giving it some time to cool, the manufacturers grind it into fine powder.
Step 2: Making of silicone
The resultant product of step 1, i.e. pure silicon powder is combined with methyl chloride. When this mixture is heated, it activates the reaction between the components forming methyl chlorosilane. Methyl chlorosilane is a mixture of a lot of components, but the main component is dimethyldichlorosilane. It is a primary building block of silicone.
A complex distillation process is required to separate the numerous components of methyl chlorosilane. After the process of distillation is complete, a combination of water with dimethyldichlorosilane causes hydrochloric acid and disilanol to separate from each other. Post this separation, hydrochloric acid starts acting as a catalyst for the disilanol, causing it to condense into polydimethylsiloxane.
Step 3: Making of silicone adhesive
In this step, silicone is polymerized for the formation of silicone adhesive. When silicone is uncured, it is a highly adhesive and non-toxic gel or liquid. The final product after the polymerization of the silicone is a flexible, heat-resistant silicone adhesive that has a wide range of applications across industries.
Types of silicone adhesive
There are many types of silicone adhesives available in the market. Despite this number, there are two main types of silicone adhesives, two-part, and single-part. The difference between these two types is the curing agent. The curing agent can decide the drying time of the adhesive.
1. RTV (Room Temperature Vulcanizing) Silicone Adhesive
RTV silicone adhesive is used for electrical insulation due to its high weather resistance properties. It is a mild adhesive that develops a cushiony texture when gluing two surfaces together. This adhesive begins to cure as soon as it is exposed to the air, unlike other silicone adhesives which take a minimum of 24 hours to cure. For this reason, it is stored in an airtight conditioner.
2. High-Temperature Silicone Adhesive
It is a liquid silicone adhesive that is present in the form of a gel in the tube. This type of silicone adhesive can survive temperatures of 600 degrees Fahrenheit or 315 degrees Celsius, along with a strong resistance to aging, vibrations, and shock. High-temperature silicone adhesive requires 24-48 hours to cure, depending on how thick the application is.
3. One-Part System Silicone Adhesive
One-part silicone adhesives are available in the market with different viscosities and optical transparency. They do not require a mix of glue and the curing agent. They contain all the benefits of silicone adhesives including their strength and flexibility. The curing rate of one-part system silicone adhesives depends on how thick the application is.
4. Silicone Rubber Adhesive
The silicone rubber adhesive is commonly used for marine applications in sealing and waterproofing boats, as silicone has watertight properties. It does not crack or deteriorate over time.
5. Fluorosilicone Adhesive
Fluorosilicone adhesive is available in one and two-part versions. It contains trifluoropropyl, thus increasing its chemical resistance to fuels, solvents, oils, and acids. This adhesive has amazing mechanical properties and bonds well with other types of chemicals. The process of curing is similar to the silicone adhesive where one part is cured itself and two part requires mixing.
6. Pressure Sensitive Silicone Adhesives (PSA)
This silicone-based adhesive is resistant to high temperatures and it adheres to low-energy substrates. It is made up of synthetic elastomers. PSA is attached to some of the material like paper, cloth, or plastic which bonds to the surface when pressure is applied.
PSAs alone have unique characteristics and can be formulated to serve a wide range of purposes such as masking tape, and screen liner film for protecting the screen from prying eyes during transportation or installation. It also is ideal because it's easy to install electronic insulation (EMI) if designed properly. They are available in a huge range of packaging and are resistant to exposure to extreme weather conditions or environments. PSAs adhere well to hard-to-wet surfaces and low-energy substrates.
PSA is strong silicone adhesive tape that can be easily removed leaving no residue. As a result, they have been developed as an adhesive that is biocompatible and hypoallergenic for bandages dressings, or surgical tape. PSAs are mainly used in the medical field because they can help to keep harmful substances from getting into wounds and prevent bad bacteria from developing during repair.
The silicone pressure adhesive has a very strong bonding power, similar to an elastic sealant with the properties of a gel. They are also flexible at lower temperatures and resistant to UV rays as well as solvents.
7. Ultraviolet-cured silicone adhesive
To initiate curing, photoinitiators are added to ultra-violet cured silicone adhesive. When the photoinitiator absorbs light with wavelength and intensity that are appropriate, then the polymerization reaction begins to take place as does the curing of silicone glue. Curing takes a few seconds and is solvent-free.
8. Fast Cure Silicone
With a two-part platinum system, fast-cure silicone does not need air or moisture to begin the process. The two parts are a vinyl functional silicone polymer with a platinum catalyst which contains a cross linker and inhibitor. Curing begins with the addition of a crosslinker to vinyl polymer. The whole curing process takes about 24 hours.
9. Aquarium Silicone Adhesive
Aquarium silicone adhesive is a vital part of aquarium repair. It can be used to seal the tank and attach rocks, plants, or decorations. Because it dries clear and is invisible, it's the perfect adhesive for aquariums. Silicone aquarium adhesive is a gel and very easy to use. Silicone aquarium adhesive is cured in about seven days but will maintain a seal even when still sticky.
What kind of materials are bonded with silicone adhesive?
Silicone adhesives are used to bond different types of materials tightly together, due to their ability to maintain the bond at a series of varied temperatures. The one major benefit of using silicone adhesives is that they can sustain the bond despite the temperature and the environment. Some of the different kinds of materials that can be bonded with the silicone adhesive are:
- Ceramic
- Rubber
- Glass
- Metal
- Wood
Conclusion
In this blog, we learned that silicone adhesive glue is the most common application of silicone across a wide range of industries. Different types of silicone adhesives are used in different industries. It has ample unique and interesting properties, which makes it the best choice for binding materials together for a long-lasting time.
Frequently Asked Questions
What is the strongest silicone adhesive?
Extreme Hold is the strongest silicone adhesive, the latest innovation in the field of adhesives in the industry.
What is RTV silicone adhesive?
RTV silicone adhesive is a type of silicone adhesive that is used for electrical insulation and is used in sealing panels, window panes, and many other materials.
What is silicone caulk adhesive?
Silicone caulk adhesive acts as a strong sealant and can be used in various applications in a versatile manner.
Where is silicone adhesive tape used?
Silicone adhesive tape is used in treatments of blisters, corns, hammer toes, diabetic wounds, and warts.