Adhesives and Glues

Adhesives and glues are used nearly across the board, from factories to household kitchens, from construction sites to kindergarten art classes. There are several ways that various adhesives can be differentiated from one another. Some are derived from natural sources and some are completely synthesized materials that come out of labs. Some adhesives harden after a chemical reaction takes place and some only need to change temperature to harden. Some only need pressure.

Adhesives have been in use for literally hundreds of thousands of years. They are advantageous options in many cases, particularly when using some form of mechanical fastening would be impractical. They come as paint-on substances, in spray cans, in stick form and in bottles with applicators. They are typically inexpensive and, in some cases, they can hold up for a lifetime, and quite often they can last far longer than that.

From prehistoric tar pits to the most advanced laboratories in the world, humankind has continually improved upon and found new uses for adhesives.


What Is Glue?

Glue is a substance that allows two surfaces to be bonded together. The term is commonly used interchangeably with “adhesive”. Glues are often marketed for specific applications—wood glue, thread lock, etc.—rather than being marketed based on their chemical compositions, such as polyurethane or epoxy.


What Is Adhesive?

An adhesive holds materials together. There are many different types, but the different types all describe essentially the same thing. Cement, glue and other terms all refer to adhesives of one sort or another.

There are natural and synthetic adhesives in use. They range from adhesives that are strong enough to hold parts of a building’s structure together to adhesives that are weak enough that they are only practical for paper and other very light surfaces that are not put under any great deal of tension.

Adhesives can also be used as coatings. This is sometimes done on surfaces that are going to be in contact with a lot of contaminants—flooring, for instance—or on surfaces that are subject to corrosion and rust.


History of Adhesives and Glues

Adhesives in one form or another have been in use for literally hundreds of thousands of years. Tar is believed to be the first adhesive that humankind used. Natural adhesives have been use in various forms since then, with not much change in there natures until recently. Everyth8ign from tree resin to plant gum has been used as glue over the years.

The Egyptians are known to have used animal gules in the production of some objects. Glues were developed further in the early first millennium by Greeks and then Romans. They began to use a variety of materials as adhesives. Mortar is a type of adhesives and this was improved by the Romans, as well.

Furniture makers and instrument makers started to use glue in their work around 1500 in Europe. Adhesives, however, for the most part, remained unchanged for many centuries. In the late 17th Century, glue was first produced on an industrial scale.

Animal glues remained popular for centuries, with fish and hides being used to produce reliable adhesives. Starch was and is still used in some applications.

Charles Goodyear mixed the first modern plastic in 1939 when he combined rubber with sulfur. The development of new adhesives frequently coincided with industrial needs. When automobiles started to become common, for instance, adhesive had to be developed to accommodate the stresses and the materials that needed to be bonded together as part of the vehicle.

Pressure sensitive adhesives are the types found on tape and other materials that can be adhered without anything more than a light press. They were developed in 1845, but have been continuously improved upon since.

Many of the most advanced synthetic adhesives were developed as a result of the world wars. These adhesives provide some of the strongest bonds and have other qualities that make them ideal for specific applications.


What Is Adhesive Used For?

Adhesives are used whenever two or more surfaces need to be affixed to one another. It is used when its particular qualities make it preferable to other means of fastening—bolts and nuts, for instance—or when the addition of an adhesive provides a more practical and better functioning bond.

Adhesives are also used in many repair applications. The consumer market, for instance, includes many types of glue that are advertised for fast drying and strong bonding properties. These are commonly used to fix broken dishes and to make other repairs that would be impossible or difficult by other means.

Adhesives are also used as coatings. They are easily spread across a surface. When they dry, they completely cover or encapsulate a surface, preventing it from coming into contact with the outside environment. This can also provide improved mechanical strength. A popular application for this is the use of adhesives to encapsulate electronic components, providing protection for that component against environmental and mechanical damage.


What Is the Difference Between Reactive Adhesives and Non-Reactive Adhesives?

Reactivity in adhesives has to do with how the adhesive actually hardens. If it hardens by way of a chemical reaction, then it is described as a reactive adhesive. If not, it is considered a non-reactive adhesive.

The easiest example of reactive adhesives to understand is a two-part adhesive, such as the tubes of epoxy that are widely available. The chemical reaction between the two parts of the adhesive is what causes it to harden. Left separate in their tubes, the two components are soft.

Hot adhesives are examples of non-reactive adhesives. In this case, the adhesive hardens as the heat used to melt it dissipates into the environment. There is no chemical reaction involved in the actual hardening of the material.


What Is the Difference Between Natural and Synthetic Adhesives?

Natural adhesives are made out of animal or vegetable materials. They may also be made out of materials gathered from the natural environment. Animal glues were used in the construction of antique instruments and it still used to repair such instruments. In modern times, synthetic adhesives have replaced animal adhesives in many applications, though other forms of natural adhesives are still very popular and useful.

In synthetic adhesives are made out of materials including thermosets and elastomers. Emulsions and thermoplastics are also used in their manufacture. They include the very fast-stetting household glues, which are chemically known as cyanoacrylate glues. Many of the very mundane applications filled by adhesives—such as the backing on tapes and sticky notepaper—employ pressure sensitive adhesives. There are many different synthetic adhesives, and they range from the strongest and most durable epoxies to some of the lightest bonding adhesives on the market.


What Types of Adhesives and Glues Exist? How Does each Type Function and What Is It Used For?


Acrylic Adhesives

Acrylic adhesives are reliable and hold up well against damage from UV light, head and the other forces that compromise glues. They are used in many different applications where a great deal of strength is needed.


Adhesive Activators, Primers & Debonders

Adhesive activators are accelerants that lower the time required for an adhesive to bond. Adhesive primers work a bit like paint primer. The adhesive primer is painted onto the surface where the glue is to be applied and helps the glue to stick. A debonder can remove adhesives from surfaces and between objects. They sometimes soften the adhesives and sometimes dissolve them altogether.


Adhesive Brushes

Adhesive brushes are particularly useful in applications where a great deal of precision needs to be exercised in the application of the glue. They can prevent problems with adhesion due to too much or too little glue being applied.


Adhesive Patch Kits

Adhesive patch kits can be used perform field repairs on equipment such as pipes. The kits usually contain the patch and a spay adhesive that bonds the patch to whatever equipment is being repaired. This may affect a permanent or temporary repair, depending upon the application.


Conductive Adhesives

These are adhesives that are capable of conducting electric current. They are commonly used in electronics to repair equipment.


Cyanoacrylate Adhesives

These adhesives are commonly known by their brand names. They are thermoplastic adhesives that can set very quickly. They provide a very secure bond, as well, making them enormously convenient. They’re popular for fast repairs and in the consumer market for range of different uses.


Epoxy Coatings

Epoxy coatings are protective coatings that are frequently used in industrial applications. They have very good durability, but are vulnerable to UV light. They can help to protect against corrosion and other environmental damage.


Epoxy Resins and Adhesives

Epoxy products generally consist of two separate resins that, when they are blended together in some proportion, provide an adhesive material. The adhesives are very strong, able to endure damage from chemicals and other threats and can hold for a long time. They are used in some of the most demanding applications for adhesives.


Glue Dots

Glue dots are a convenient way to dispense glue. The dot is merely a small quantity of glue that is applied to a surface—usually paper or plastic—that needs to be adhered to another surface. They are inexpensive and widely used in arts and crafts.


Glue Sticks

Glue sticks are quantities of glue that are usually dispensed in a tube. The glue is solid enough at room temperature to allow it to keep its shape, but can be applied to surfaces by dragging it across them. This is a popular, low mess way to dispense glue for craft and office use.


Polyester Resins and Adhesives

Polyester resins very versatile materials that are used in myriad applications, including laminating and more. Polyester adhesives use this material to form very strong bonds that are resistant to environmental and chemical attacks. These are commonly used in the construction field, and are used in the manufacture of optics as well.


Polyurethane Glues

These types of glues are made out of urethane polymers. They are remarkable for being very elastic. These glues can hold up to a lot of deformation and still keep their bonds. These glues tend to be quite strong. They are used in woodworking and construction and in some other applications.


Polyvinyl Acetate Adhesives

This group of adhesives is used in woodworking, for craft purposes and in construction. They are commonly used on porous surfaces and objects.


Potting Compounds

Potting compounds are used in electronics as a way to protect components. They consist of two parts that are usually poured over the components to completely encapsulate them.


Rubber and Contact Adhesives

These are also known by the name rubber cement and contact cement. They provide a very quick-setting bond. The compound includes neoprene rubber, which comprises part of the name for some brands, as well.


Spray Adhesives

Spray adhesives are commonly used in arts and crafts, though they have industrial and heavy-duty applications, as well. The method of application is what defines these adhesives and they are enormously convenient.


Surface Mount and Silicone Adhesives

These are adhesives used in electronics. They bond the components of a printed circuit board (PCB) to the board itself. They are often fast drying and dispensed in syringes and other forms that are convenient for their applications.


Thermal Adhesives

Thermal adhesives are used in electronics and in other applications. They are able to transfer heat between the surfaces to which they are bonded. They are used, for example, to transfer heat from a processor to the heat sink to which it is attached.


Threadlocking Adhesives

Threadlocking adhesives are used to provide improved seals between threaded pipes, bolts and nuts and other surfaces where leakage and loosening might be issues. They can create a very effective seal and come in a variety of different strengths and types suitable for different applications.


Vehicle Maintenance Adhesive Kits

These are adhesives made to repair or improve equipment on a vehicle. They are often used in conjunction with gaskets and help to provide a better seal between the parts that are joined together, preventing leakage.