What Type of Bonding is there in Rubber?

Alex Williams
11 Min Read

Having a good bonding with someone is something that everyone cannot achieve easily. However, emotional and mental bonding is a social trait and need for humans. Talking about materialistic things, various means create a bond between them. Here bond means elements or atoms are joined with other elements to form a complex structure. Today I am talking about rubber bonding. Do you know what type of bonding is there in rubber? Is rubber ionic or covalent bond? How do you bond rubber? Let’s begin and find the answers.

1. What are the Different types of Rubber?

The basic categorization of rubber is natural and synthetic (man-made). But, there are different types of synthetic rubber that are used for different purposes. Here are some of the basic rubber types:

  • Butyl Rubber: It is highly flexible and used in seals, toppers, inner linings, inner tubes, linings, and valve seating.
  • Ethylene Propylene Diene Monomer (EPDM): It is highly durable and flexible, this is why it is used in seals (windows and doors), non-slip coatings (decks), cold rooms, automotive hoses, etc.
  • Natural Rubber: It occurs naturally and is used in seals, gaskets, mountings, carpet backing, surgical gloves, car tires, pacifiers, toys, etc.
  • Nitrile Rubber: It is highly resistant compared to natural rubber and has superior strength but the least flexibility. It is used in automotive transmission belts, hoses, v-belts, synthetic leather, cable jacketing, O-rings, conveyor belts, etc.
  • Polyurethane Rubber: It is resistant to tear and cut along with abrasion. This rubber is used in plastic, outlast metal, modeling, molds, etc.
  • Silicone Rubber: This rubber is highly resistant to temperature, radiation, and chemicals; this is why it has food and medical-grade ratings. It is used in ovenware, cookware, medical devices, prosthetics, gaskets, etc. 

2. What is Bonding?

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For materials or things, the word bonding means the action to join things securely to another thing. This can be done with the help of an adhesive, pressure, or heat. Sometimes changing the chemical bonding can also help in bonding things. Read the next segment to know what type of bonding is there in rubber. (See Why do atoms form chemical bonds?)

3. What Type of Bonding is there in Rubber?

A rubber is constituted of elastic polymers, also known as elastomers. They are large chain-like molecules that are highly elastic and can be stretched to great lengths. They have the tendency to return to their original shape after you stop stretching. So, what type of bonding is there in rubber? The bonding in rubber is covalent with Van der Waals force. The group of interactions between atoms or within molecules taking place when electron clouds interact with each other is known as the Van der Waals force. The interactions usually take place surrounding the poles. (See How many Oxygen Atoms are in SiO2?)

4. What is Atomic Bonding?

Every living and non-living thing is made up of atoms. Atom is the basic unit and the force that holds these atoms together is the inter-atomic bonds. Understanding different types of bonding are useful while learning about what type of bonding is there in rubber. It is an important determinant of material properties, and it is of three types namely, covalent, ionic, and metallic. But most materials lack pure bonding of the mentioned three types, and some can have other types of bonding too. Like in some metals there is metallic bonding, but traces of covalent bonding are also noticed in it. The types are:

  • Covalent Bonding: A bond is formed when two or more particular atoms share the valence electrons from one atom. This bond is known as a covalent bond and polymers are an example of such a bond. A material made from polymers is nylon rope. Polymer structures are long chains of covalent bonds containing carbon and hydrogen atoms in different arrangements.
  • Ionic Bonding: A bond formed with the transfer of valence electrons from one atom to another atom and completes the outer electron shell is known as ionic bonding. Salt is an example of ionic bonding because of the simple molecular arrangement of NaCl.
  • Metallic Bonding: When there is no association of the valence electrons with another particular ion or atom, but it exists around the ion centers as a cloud of electrons, this type of bonding is known as metallic bonding. For example, iron and other metals are considered to have metallic bonding. 

5. Is Rubber Ionic or Covalent?

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It is covalent with Van der Waals force. Rubber is an elastomer, and it occurs naturally as well as it is synthetically produced. It has 2-methyl, and 1 3-butadiene atom, making it an isoprene. This structure of rubber and the molecular arrangements along with the interactions between the ions defines that the bond in rubber is covalent. (See What are Carbohydrates Monomer and Polymer?)

6. How do you Bond Rubber?

There have been instances where you had the need to bond rubber with rubber or other materials. But different techniques and adhesives are required for bonding different types of rubbers according to the knowledge regarding what type of bonding is there in rubber. This is because not every rubber has the same composition. EPDM rubber, polyurethane rubber, nitrite rubber, silicone rubber, natural rubber, and butyl rubber are a few types of rubber that you can bond. Here are the steps that can be followed if you are trying to bond the rubber:

  • Prepare the Rubber for Bonding: Irrespective of the rubber that you are using, preparing it is the first thing that needs to be done. You need to begin by degreasing the surface of the rubber with some degreasing solvent. It will remove mold, slip additives, or any other processing lubricants. Isopropanol is considered the best degrease because acetone can be too strong for some rubbers.
  • Selecting the Adhesive: You must have heard the name superglue, which can stick to almost everything quickly and strongly. This is the case with rubber also, superglue scientifically known as cyanoacrylate instant adhesive, is considered the best choice for rubbers too. A small amount of adhesive is required to bond the rubber together. However, sometimes, the bond does not stay and hold together. This happens because some types of rubber do not bond with this glue, like silicone rubber or natural rubber. 

7. How to Bond Natural and Synthetic Rubber?

After understanding what type of bonding is there in rubber, is it not useful to know ways to bond natural and synthetic rubber?

Ethylene Propylene Diene Monomer (EPDM) or natural rubber ASI RP Series Cyanoacrylate Super Glue can be used. It is another type of cyanoacrylate adhesive that is especially effective for plastics and rubbers. However, while working with silicone rubber, you need to first apply a primer and then put the adhesive. Permabond POP primer is considered for this rubber. (See What is a Drop of Liquid Mercury?)

8. How to Bond Rubber to Other Substances?

If you need to bond rubber to glass, metal, or plastic, it is necessary to consider the properties of the elements. Cyanoacrylate may be useful mostly but while bonding plastic with rubber, it does not work, as the adhesive can eat the plastic. An epoxy adhesive can be a better option in this situation when you are bonding rubber with other materials, namely metal, and glass. However, they do not work on rubber-to-rubber bonding. (See What Tools do Forensic Scientists Use?)

9. What is Silicone Adhesive?

This adhesive is highly versatile and can be used to bond silicone rubber with other materials too. It is used in many industries. The properties of silicone adhesive are as follows:

  • It is resistant to Ultraviolet rays (UV), chemicals, moisture, and temperature.
  • It is highly flexible and does not break or wear off.
  • It can act as a good conductor and insulator of electricity, depending upon the situation and product it is applied to.

So, today you learned about what type of bonding is there in rubber. How do you bond rubber? The answer to this is hidden in the type of rubber and properties of the material that you are bonding together. Did you notice whether is rubber ionic or covalent? (See What is Silicon Made of?)

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