[Physics Class Notes] on Elastomers Pdf for Exam

What are Elastomers?

Every day we are dependent upon products and use them as have developed through experimentation and discovery.  Having knowledge that evolves regarding the chemical properties, we understand the benefits of developing new products, including products that are made of elastomers.

Countless things like the tires allow the smooth movement of the car over the road. Also, the rubber storage containers in our kitchen and many things with flexible molecular structures are all elastomers. What makes these objects flex and return to original shape? Why are some products rigid compared to others? What holds these structures together? Let us learn more about elastomers.

Elastomers Definition

In chemistry, material made of a long chain of molecules is known as polymer and elastomer. It is known as the polymer having both viscous and elastic properties. A substance which is thick, sticky, and consistent somewhere between the solid and gas stage are known as viscous. How fast or slow a liquid flow is determined by the viscosity of the liquid. When you pour oil from a container, you will see that it pours much slower compared to water, since it is more viscous.

Properties of Elastomers

In chemistry, the bonds that hold several compounds together are very strong compared to size. The flexibility of the object is determined by the bond force and the compound’s ability to manipulate into different shapes.

• Comparatively, elastomers intermolecular forces are weak. The forces of repulsion and attraction between molecules and other particles are known as intermolecular forces.

• As elastomers are not tightly bonded together by attraction to their nucleus, they can stretch apart and have higher failure strain than many other compounds.

• The material that will fail at a molecular level when stain is imparted on them, they are known as non-elastic compounds.

• The elements used to make elastomers are carbon, silicon, hydrogen, and oxygen, which hold together well in different conditions.

Categories of Elastomers

As a consensus, there are two categories of elastomers:

When heated, thermoset elastomers do not melt. When exposed to different types of environmental conditions, they retain their structure. This property of elastomers makes them very useful in different industries where heat and pressure are applied at various levels since they will not break down.

Whereas, thermoplastic elastomers can be melted and reformed into different shapes and configured as per requirement and their use. E.g., you can think of a stick of butter when picturing thermoplastic elastomers. The stick can be cooled and melted many times and molded into different shapes while retaining its original properties.

Elastomers Examples

In manufacturing processes like injection molding, thermoplastic elastomers are used. Thermoplastic polyurethanes are used in many applications, including production of foam seating, seals, gaskets, etc.

All types of saturated and unsaturated rubbers and polysulfide rubbers

•  Natural Rubber – This is used in the manufacture of gaskets, shoe heels…

• Polyurethanes – This material is used in the textile industry for manufacturing elastic clothing such as lycra is also used as foam, wheels, etc.

• Polybutadiene – This type of elastomer material is used on wheels or tires of vehicles, giving them extraordinary resistance to wear and tear.

• Neoprene – This material is primarily used in manufacturing of wetsuits and is also used as wire insulation, industrial belts, etc.

• Silicone – This material is used in a variety of materials and areas since they have excellent chemical and thermal resistance. Silicon is used in manufacture of medical prostheses, pacifiers, lubricants, mold, etc.

Types of Elastomers

Following are the two types of elastomers:

1. Saturated elastomers

2. Unsaturated elastomers

Unsaturated Elastomers:

By using sulfur vulcanization unsaturated elastomers can be cured, and non-sulfur vulcanization is desired, for examples:

• Synthetic polyisoprene

• Butadiene rubber

• Neoprene rubber

• Nitrile rubber

• Butyl rubber

Saturated Elastomers:

This type of elastomers cannot be cured by sulphur vulcanization process, for examples:

• Ethylene propylene rubber (EPR)

• Ethylene-vinyl acetate (EVA)

• Polyacrylic rubber

• Silicone rubber

• Fluoroelastomers

• Polyether block amides.

• Chlorosulfonated polyethylene rubber

Do you know?

Elastomers are used to manufacture duckbills and diaphragms of plastic diaphragm check valves; also, O-rings and gasket seals. This is because of its unique physical and chemical properties. Most designing processes can benefit from a better understanding of elastomeric materials.