Physical Properties of Rubber

13 May.,2024

 

Physical Properties of Rubber

What are the physical properties of rubber?

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These are the physical properties of rubber.

  • Hardness
  • Tensile Strength
  • Tensile Modulus
  • Elongation
  • Resilience
  • Compression Set
  • Tear Resistance
  • Abrasion Resistance
  • Specific Gravity

The following sections provide a high-level look at each physical property. Future articles in this series will examine each property in greater detail.

Hardness

Elastomers have an inherent hardness because of their chemical structure. This hardness can be modified, and the processed hardness then measured in terms of durometer (duro) on a Shore scale. For soft to medium-hard rubber, Shore A is used. At 40 duro, solid rubber profiles have the consistency of pencil erasers. At 90 duro, they’re hard like hockey pucks. Which hardness do you need?

Tensile Strength

Tensile strength (TS) is the amount of force that’s required to pull a rubber specimen apart until it breaks. Known also as ultimate tensile strength (UTS), TS is measured in either pounds per square inch (psi) or megapascals according to ASTM D412. For technical buyers and part designers, tensile strength matters because it represents a rubber’s point of failure caused by stretching.

Tensile Modulus

Tensile modulus (TM) sounds similar to tensile strength, but these two properties are not the same. TM is the force or stress that’s required to produce an elongation percentage or strain in a rubber sample. In general, harder rubber has a higher tensile modulus. Such rubber is more resilient, but also more resistant to extrusion, a process for manufacturing stock materials used in custom fabrication.

Elongation

Elongation is the percentage increase (strain) in the original length of a rubber sample where a tensile force (stress) is applied. Some elastomers stretch more than others. For example, natural rubber (NR) may stretch up to 700% before reaching its ultimate elongation, the moment the NR breaks. By contrast, fluoroelastomers may rupture at 300% elongation. How much do you need your rubber parts to stretch?

Resilience

Resilience or rebound refers to a rubber’s ability to regain its original shape and size after a temporary deformation, such as contact with a metal surface. Resilience is especially important in dynamic seals, components that create a barrier between moving and stationary surfaces. If your application requires weatherstripping between a door and a door frame, the compound’s resilience is important to consider.

Compression Set

Compression set is the amount by which an elastomer fails to return to its original thickness after a compressive load is released. When a rubber seal is compressed repeatedly over time, progressive stress relaxation occurs. In terms of the seal’s life, stress relaxation is like dying. Compression set is like death itself – the end result of a steady decline in sealing force. How long do you need your seal to last?

Tear Resistance

Tear resistance describes an elastomer’s resistance to the growth of a nick or cut when tension is applied. Also known as tear strength, this physical property is measured in either pound force per inch (lbf/in) or kilonewtons per meter (kN/m). If you need edge trim that will contact rough metal edges or sharp objects, consider tear resistance during compound selection.

Abrasion Resistance

Abrasion resistance describes a rubber’s resistance to being worn away from rubbing or scraping. In industrial applications, abrasion-resistant rubber is used with conveyor belts that move coal and in pumps that handle slurries. Material loss due to abrasion can be measured with various instruments according to tests such as ASTM D394.

Specific Gravity

Specific gravity is the ratio of the weight of a material to the weight of an equal volume of water at a specified temperature. For chemists, it provides a way to identify compounds. For technical buyers and part designers, it’s important to know that rubber with a low specific gravity offers more square inches per pound of stock. Rubber with a higher specific gravity provides advantages in molding consistency.

Do you need custom seals? Learn more about the physical properties of rubber.

Do you have questions about the physical properties of rubber? Contact Elasto Proxy for more information, and enjoy the short video below that accompanies this article.

Rubber Gasket General Design Guide

If you are working in manufacturing, auto, food processing, pharmaceutical, aerospace, medical, energy, construction or any other industrial sector, you mostly be aware of the role that a gasket plays in many aspects of this industry. Since its inception, rubber gaskets become critical component of industrial world & found its place in the industry. It also has come a long way in terms of technological development as well.

In this article, we will discuss more about gaskets, the applications of rubber gaskets as well as some of the most significant factors you should consider while designing one for your needs.

What is a Gasket?

A gasket in the most simple of terms can be defined as being a mechanical seal which can be used to fill the gap between two joints. The main purpose of using a gasket is to achieve a perfect seal between two mating components, which are not so perfect. Along with this, the use of a gasket also prevents the leakage of liquids and other materials into the mating surfaces and out from it, thus contributing to keeping the transfer of materials safe and secure. Gasket also provide effective solution for controlling & dampening vibrations, providing insulation, preventing electromagnetic interference (EMI), supporting mounts & reducing surrounding sound.

How Does a Gasket Work?

As you can understand from the definition of a gasket, its job seems quite simple however many times working condition as well as surrounding environment makes it very challenging. Its basic job is to provide robust seal between two mating surfaces in such a way so that there is no leakage whatsoever. Depending upon the material that is being used to make the gasket, it can be used to serve in many applications, the most common being sealing.

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Today there are more than 1200 different materials from which gaskets are manufactured, and depending on your project, application & budgeting needs, you can choose any one of them. Among all the available gasket making materials, the most common are rubber, plastic, metal, cork, and hardened paper, etc..

Applications of Rubber Gaskets

Rubber gaskets are undoubtedly one of the most popular gasket in the industry. Thanks to the diverse properties & unique attributes that rubber brings to the table, a rubber gasket can be used to fulfill a variety of sealing needs and applications.

One application where rubber gaskets are most commonly used is the fluid transfer application. The pipes, hose or tubing that transport the fluid from one point to another are often connected by the use of rubber gaskets so that there is no leakage from the joints.

We can easily say that depending upon the type of gasket one is using, its application can be defined, but in most cases, it is used to safely transport fluids from one point to another without any spillage or leaks.

What Kind of Rubber Materials Can Be Used for Making a Gasket?

There are a variety of rubber materials available in the market that are used to make rubber gaskets. Some of the most significant ones are as mentioned below.

1. EPDM : EPDM offers excellent resistance for weathering, water and aging which makes it very popular elastomer for indoor as well as out door application.

2. Silicone Rubber : When you need gasket which can supports wide temperature range or complies in food & health environment or provide electrical insulation silicone is perfect choice for those gasket. It also offers excellent resistance to sunlight, ozone & radiation.

3.Buna-N or Nitrile Rubber: Buna N is a general-purpose rubber which has a temperature range of -65 to 300 degrees F and is most commonly used for making gaskets.

4. Fluorocarbon: After Buna N, this is the most common form of rubber that is used to make gaskets. Most commonly known as Viton in the industry, this is an all-purpose rubber that has a temperature range of -55 to 385 degrees F.

5. Neoprene: The third variety of rubber that is used to manufacture rubber gaskets is Neoprene, which has a low-temperature range and is mostly used in applications where extreme low-temperature conditions can be expected.

What Factors Need to Be Considered While Designing a Gasket?

Now that you know of the different types of rubbers that are used in the gasket manufacturing process, here are a few points to be consider while designing one for your needs.

1. Operating Condition: This is the first factor you need to look into when you sit down to design a gasket. Consider the type of weather and temperature range, your gasket will be exposed to in its lifetime because the wear and tear, as well as the shelf life of the gasket, will be dependent on this. Also needs to consider if there is operating pressure and any kind of movement and speed for sealing environment.

2. Machine Assembly: The second aspect to consider is where & why your gasket will be used. Will it be used to seal pipes together or seal enclosure or create air tight space or reduce vibration or insulate heat & noise or something else? Depending on the most specific application & location of gasket, its design & material specifications need to be changed.

3. What needs to be sealed: The third most important factor that you need to consider is the type of liquid, gas or chemical that the gasket will get exposed to. For example, designing gasket for sealing gas is difficult than a liquid. After determining temperature & pressure range it is very important to check chemical resistance of gasket material because it directly impacts structural & functional properties of gasket. Sometime temperature makes the fluids more aggressive which can adversely affect gasket performance.

We at Accurate Rubber Corporation are one of the premium manufacturers & supplier of rubber gasket & seal for all different needs. Please contact us today if you need more information about rubber gasket or have some project which requires rubber gasket or other rubber parts.

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